Set I - Atmospheric Model high resolution 10-day forecast (HRES)

 Configure and order Set I

Single prediction that uses

  • observations
  • prior information about the Earth-system
  • ECMWF's highest-resolution model

HRES Direct model output Products offers "High Frequency products"  

  • 4 forecast runs per day (00/06/12/18) (see dissemination schedule for details)
  • Hourly steps to step 90 for all four runs

Post-processed Products are not available at 06/18 runs or in hourly steps.

The purchase of the "Basic Set" +72, +96, +120, +144, +168 hrs is a mandatory prerequisite for the purchase of time steps in the range 12 to 66 hours.

The following sub-sets are available from the HRES (High Resolution) Model (previously "Deterministic Atmospheric Model") :

I-i: Atmospheric fields (Direct model output)

I-ii: Time series of weather parameters (Post-processed output)

I-iii Tropical cyclones tracks (Post-processed output)

Tropical cyclones tracks products are provided in BUFR code free of information charge.

I-iv Simulated satellite data (Post-processed output)

Product description

  • 0.1° x 0.1° lat/long grid or any multiple thereof (global or sub-area)
  • On model (Octahedral) O1280 grid (global or sub-area)
  • Spectral components (TCO1279) for upper-air fields (global area only)

The products are provided in GRIB code except I-ii Time series of weather parameters and I-iii Tropical cyclones tracks that are provided in BUFR code.

See What is the format of the data?

Dissemination schedule

I-i: Atmospheric fields

Forecast Runs (base time) Forecast step frequency Forecast Dissemination schedule Forecast Dissemination stream indicator*
00 UTC
  • 0 to 90 by 1
  • 93  to 144 by 3
  • 150 to 240 by 6
  • 5:45 --> 6:12
  • 6:12 --> 6:27
  • 6:27 --> 6:55
  • S
  • D
  • D
06 UTC
  • 0 to 90 by 1
  • 11:45 --> 12:12
  • S
12 UTC
  • 0 to 90 by 1
  • 93 to 144 by 3
  • 150 to 240 by 6
  • 17:45 --> 18:12
  • 18:12 --> 18:27
  • 18:27 --> 18:55
  • S
  • D
  • D
18 UTC
  • 0 to 90 by 1
  • 23:45 --> 00:12
  • S

 

Analysis Runs (base time) Analysis Dissemination schedule Forecast Dissemination stream indicator
00 UTC
  • 5:40
  • D
06 UTC
  • 11:40
  • 17:35
  • S
  • D
12 UTC
  • 17:40
  • D
18 UTC
  • 23:40
  • 5:35
  • S
  • D

*for more information: Real-time data - file naming convention format

I-ii: Time series of weather parameters (Post-processed Products)

 

Weather Parameter Products Time available
12 UTC based 18:55
00 UTC based 06:55

 I-iii Tropical cyclones (Post-processed Products)

(dissemination data stream indicator = C)

Tropical cyclone products Time available
12 UTC based 18:55
00 UTC based 06:55

I-i: Atmospheric fields (Direct model output)

Single level - analysis

Analysis fields can be provided for base time 00, 06, 12 or 18

Short Name ID Long Name Description Units Additional information
aluvp 15 UV visible albedo for direct radiation Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the fraction of direct solar (shortwave) radiation with wavelengths shorter than 0.7 µm (microns, 1 millionth of a metre) reflected by the Earth's surface (for snow-free land surfaces only). It is one of four components (parameters 15-18) that were used by the ECMWF Integrated Forecasting System (IFS) to represent albedo up to and including Cycle 46R1. Later cycles use instead six components (parameters 210186-210191). See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).

In the IFS, a climatological (observed values averaged over a period of several years) background albedo is used which varies from month to month through the year, modified by the model over water, ice and snow.
(0 - 1)  
aluvd 16 UV visible albedo for diffuse radiation Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the fraction of diffuse solar (shortwave) radiation with wavelengths shorter than 0.7 µm (microns, 1 millionth of a metre) reflected by the Earth's surface (for snow-free land surfaces only). It is one of four components (parameters 15-18) that were used by the ECMWF Integrated Forecasting System (IFS) to represent albedo up to and including Cycle 46R1. Later cycles use instead six components (parameters 210186-210191). See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).

In the IFS, a climatological (observed values averaged over a period of several years) background albedo is used which varies from month to month through the year, modified by the model over water, ice and snow.
(0 - 1)  
alnip 17 Near IR albedo for direct radiation Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the fraction of direct solar (shortwave) radiation with wavelengths longer than 0.7 (microns, 1 millionth of a metre) reflected by the Earth's surface (for snow-free land surfaces only). It is one of four components (parameters 15-18) that were used by the ECMWF Integrated Forecasting System (IFS) to represent albedo up to and including Cycle 46R1. Later cycles use instead six components (parameters 210186-210191). See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).

In the IFS, a climatological (observed values averaged over a period of several years) background albedo is used which varies from month to month through the year, modified by the model over water, ice and snow.
(0 - 1)  
alnid 18 Near IR albedo for diffuse radiation Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the fraction of diffuse solar (shortwave) radiation with wavelengths longer than 0.7 µm (microns, 1 millionth of a metre) reflected by the Earth's surface (for snow-free land surfaces only). It is one of four components (parameters 15-18) that were used by the ECMWF Integrated Forecasting System (IFS) to represent albedo up to and including Cycle 46R1. Later cycles use instead six components (parameters 210186-210191). See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).

In the IFS, a climatological (observed values averaged over a period of several years) background albedo is used which varies from month to month through the year, modified by the model over water, ice and snow.
(0 - 1)  
cl 26 Lake cover This parameter is the proportion of a grid box covered by inland water bodies (lakes, reservoirs, rivers) and coastal waters. Values vary between 0: no inland or coastal water body, and 1: grid box is fully covered with inland or coastal water body. This field is specified from observations and is constant in time.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
(0 - 1)  
cvl 27 Low vegetation cover This parameter is the fraction of the grid box (0-1) that is covered with vegetation that is classified as 'low'.

This is one of the parameters in the model that describes land surface vegetation. 'Low vegetation' consists of crops and mixed farming, irrigated crops, short grass, tall grass, tundra, semidesert, bogs and marshes, evergreen shrubs, deciduous shrubs, and water and land mixtures.
(0 - 1)  
cvh 28 High vegetation cover This parameter is the fraction of the grid box (0-1) that is covered with vegetation that is classified as 'high'.

This is one of the parameters in the model that describes land surface vegetation. 'High vegetation' consists of evergreen trees, deciduous trees, mixed forest/woodland, and interrupted forest.
(0 - 1)  
tvl 29 Type of low vegetation This parameter indicates the 10 types of low vegetation recognised by the ECMWF Integrated Forecasting System:

1 = Crops, Mixed farming

2 = Grass

7 = Tall grass

9 = Tundra

10 = Irrigated crops

11 = Semidesert

13 = Bogs and marshes

16 = Evergreen shrubs

17 = Deciduous shrubs

20 = Water and land mixtures

They are used to calculate the surface energy balance and the snow albedo.

The other types (3, 4, 5, 6, 18, 19 and 19) are high vegetation, or indicate no land surface vegetation (8 = Desert, 12=Ice caps and Glaciers, 14 = Inland water, 15 =Ocean).
~  
tvh 30 Type of high vegetation This parameter indicates the 6 types of high vegetation recognised by the ECMWF Integrated Forecasting System:

3 = Evergreen needleleaf trees

4 = Deciduous needleleaf trees

5 = Deciduous broadleaf trees

6 = Evergreen broadleaf trees

18 = Mixed forest/woodland

19 = Interrupted forest

They are used to calculate the surface energy balance and the snow albedo.

The other types (1, 2, 7, 9, 10, 11, 13, 16, 17 and 20) are low vegetation, or indicate no land surface vegetation (8 = Desert, 12=Ice caps and Glaciers, 14 = Inland water, 15 =Ocean).
~  
ci 31 Sea ice area fraction This parameter is the fraction of a grid box which is covered by sea ice. Sea ice can only occur in a grid box which includes ocean or inland water according to the land sea mask and lake cover, at the resolution being used. This parameter can be known as sea-ice (area) fraction, sea-ice concentration and more generally as sea-ice cover.

Coupled atmosphere ocean simulations of the ECMWF Integrated Forecasting System (IFS) predict the formation and melting of sea ice. Otherwise, in analyses and atmosphere only simulations, sea ice is derived from observations, but the model does take account of the way that sea ice alters the interaction between the atmosphere and ocean.

Sea ice is frozen sea water which floats on the surface of the ocean. Sea ice does not include ice which forms on land such as glaciers, icebergs and ice-sheets. It also excludes ice shelves which are anchored on land, but protrude out over the surface of the ocean. These phenomena are not modelled by the IFS.

Long-term monitoring of sea ice is important for understanding climate change. Sea ice also affects shipping routes through the polar regions.
(0 - 1)  
asn 32 Snow albedo This parameter is a measure of the reflectivity of the snow-covered part of the grid box. It is the fraction of solar (shortwave) radiation reflected by snow across the solar spectrum.

The ECMWF Integrated Forecast System represents snow as a single additional layer over the uppermost soil level.

This parameter changes with snow age and also depends on vegetation height. For low vegetation, it ranges between 0.52 for old snow and 0.88 for fresh snow. For high vegetation with snow underneath, it depends on vegetation type and has values between 0.27 and 0.38. See further information.
(0 - 1)  
rsn 33 Snow density This parameter is the mass of snow per cubic metre in the snow layer.

The ECMWF Integrated Forecast System (IFS) model represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box.

See further information on snow in the IFS.
kg m**-3  
sst 34 Sea surface temperature This parameter is the temperature of sea water near the surface.

This parameter is taken from various providers, who process the observational data in different ways. Each provider uses data from several different observational sources. For example, satellites measure sea surface temperature (SST) in a layer a few microns thick in the uppermost mm of the ocean, drifting buoys measure SST at a depth of about 0.2-1.5m, whereas ships sample sea water down to about 10m, while the vessel is underway. Deeper measurements are not affected by changes that occur during a day, due to the rising and setting of the Sun (diurnal variations).

Sometimes this parameter is taken from a forecast made by coupling the NEMO ocean model to the ECMWF Integrated Forecasting System. In this case, the SST is the average temperature of the uppermost metre of the ocean and does exhibit diurnal variations.

See further documentation .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
istl1 35 Ice temperature layer 1 This parameter is the sea-ice temperature in layer 1 (0 to 7cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
istl2 36 Ice temperature layer 2 This parameter is the sea-ice temperature in layer 2 (7 to 28 cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
istl3 37 Ice temperature layer 3 This parameter is the sea-ice temperature in layer 3 (28 to 100 cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
istl4 38 Ice temperature layer 4 This parameter is the sea-ice temperature in layer 4 (100 to 150 cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
swvl1 39 Volumetric soil water layer 1 This parameter is the volume of water in soil layer 1 (0 - 7cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl2 40 Volumetric soil water layer 2 This parameter is the volume of water in soil layer 2 (7 - 28cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl3 41 Volumetric soil water layer 3 This parameter is the volume of water in soil layer 3 (28 - 100cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl4 42 Volumetric soil water layer 4 This parameter is the volume of water in soil layer 4 (100 - 289cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
slt 43 Soil type This parameter is the texture (or classification) of soil used by the land surface scheme of the ECMWF Integrated Forecast System to predict the water holding capacity of soil in soil moisture and runoff calculations. It is derived from the root zone data (30-100 cm below the surface) of the FAO/UNESCO Digital Soil Map of the World, DSMW (FAO, 2003), which exists at a resolution of 5' X 5' (about 10 km).

The seven soil types are:
Coarse 1
Medium 2
Medium fine 3
Fine 4
Very fine 5
Organic 6
Tropical organic 7
~  
lai_lv 66 Leaf area index, low vegetation This parameter is the surface area of one side of all the leaves found over an area of land for vegetation classified as 'low'. This parameter has a value of 0 over bare ground or where there are no leaves. It can be calculated daily from satellite data. It is important for forecasting, for example, how much rainwater will be intercepted by the vegetative canopy, rather than falling to the ground.

This is one of the parameters in the model that describes land surface vegetation. 'Low vegetation' consists of crops and mixed farming, irrigated crops, short grass, tall grass, tundra, semidesert, bogs and marshes, evergreen shrubs, deciduous shrubs, and water and land mixtures.
m**2 m**-2  
lai_hv 67 Leaf area index, high vegetation This parameter is the surface area of one side of all the leaves found over an area of land for vegetation classified as 'high'. This parameter has a value of 0 over bare ground or where there are no leaves. It can be calculated daily from satellite data. It is important for forecasting, for example, how much rainwater will be intercepted by the vegetative canopy, rather than falling to the ground.

This is one of the parameters in the model that describes land surface vegetation. 'High vegetation' consists of evergreen trees, deciduous trees, mixed forest/woodland, and interrupted forest.
m**2 m**-2  
sdfor 74 Standard deviation of filtered subgrid orography Climatological field (scales between approximately 3 and 22 km are included) m  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
sp 134 Surface pressure This parameter is the pressure (force per unit area) of the atmosphere on the surface of land, sea and in-land water.

It is a measure of the weight of all the air in a column vertically above the area of the Earth's surface represented at a fixed point.

Surface pressure is often used in combination with temperature to calculate air density.

The strong variation of pressure with altitude makes it difficult to see the low and high pressure systems over mountainous areas, so mean sea level pressure, rather than surface pressure, is normally used for this purpose.

The units of this parameter are Pascals (Pa). Surface pressure is often measured in hPa and sometimes is presented in the old units of millibars, mb (1 hPa = 1 mb= 100 Pa).
Pa  
tcw 136 Total column water This parameter is the sum of water vapour, liquid water, cloud ice, rain and snow in a column extending from the surface of the Earth to the top of the atmosphere. In old versions of the ECMWF model (IFS), rain and snow were not accounted for. kg m**-2  
tcwv 137 Total column water vapour This parameter is the total amount of water vapour in a column extending from the surface of the Earth to the top of the atmosphere.

This parameter represents the area averaged value for a grid box.
kg m**-2  
stl1 139 Soil temperature level 1 This parameter is the temperature of the soil at level 1 (in the middle of layer 1).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
sd 141 Snow depth This parameter is the depth of snow from the snow-covered area of a grid box.

Its units are metres of water equivalent, so it is the depth the water would have if the snow melted and was spread evenly over the whole grid box. The ECMWF Integrated Forecast System represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box.

See further information.
m of water equivalent  
chnk 148 Charnock This parameter accounts for increased aerodynamic roughness as wave heights grow due to increasing surface stress. It depends on the wind speed, wave age and other aspects of the sea state and is used to calculate how much the waves slow down the wind.

When the atmospheric model is run without the ocean model, this parameter has a constant value of 0.018. When the atmospheric model is coupled to the ocean model, this parameter is calculated by the ECMWF Wave Model.
~  
msl 151 Mean sea level pressure This parameter is the pressure (force per unit area) of the atmosphere adjusted to the height of mean sea level.

It is a measure of the weight that all the air in a column vertically above the area of Earth's surface would have at that point, if the point were located at the mean sea level. It is calculated over all surfaces - land, sea and in-land water.

Maps of mean sea level pressure are used to identify the locations of low and high pressure systems, often referred to as cyclones and anticyclones. Contours of mean sea level pressure also indicate the strength of the wind. Tightly packed contours show stronger winds.

The units of this parameter are pascals (Pa). Mean sea level pressure is often measured in hPa and sometimes is presented in the old units of millibars, mb (1 hPa = 1 mb = 100 Pa).
Pa  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
sdor 160 Standard deviation of orography This parameter is one of four parameters (the others being angle of sub-gridscale orography, slope and anisotropy) that describe the features of the orography that are too small to be resolved by the model grid. These four parameters are calculated for orographic features with horizontal scales comprised between 5 km and the model grid resolution, being derived from the height of valleys, hills and mountains at about 1 km resolution. They are used as input for the sub-grid orography scheme which represents low-level blocking and orographic gravity wave effects.

This parameter represents the standard deviation of the height of the sub-grid valleys, hills and mountains within a grid box.
m  
isor 161 Anisotropy of sub-gridscale orography This parameter is one of four parameters (the others being standard deviation, slope and angle of sub-gridscale orography) that describe the features of the orography that are too small to be resolved by the model grid. These four parameters are calculated for orographic features with horizontal scales comprised between 5 km and the model grid resolution, being derived from the height of valleys, hills and mountains at about 1 km resolution. They are used as input for the sub-grid orography scheme which represents low-level blocking and orographic gravity wave effects.

This parameter is a measure of how much the shape of the terrain in the horizontal plane (from a bird's-eye view) is distorted from a circle.

A value of one is a circle, less than one an ellipse, and 0 is a ridge. In the case of a ridge, wind blowing parallel to it does not exert any drag on the flow, but wind blowing perpendicular to it exerts the maximum drag.
~  
anor 162 Angle of sub-gridscale orography This parameter is one of four parameters (the others being standard deviation, slope and anisotropy) that describe the features of the orography that are too small to be resolved by the model grid. These four parameters are calculated for orographic features with horizontal scales comprised between 5 km and the model grid resolution, being derived from the height of valleys, hills and mountains at about 1 km resolution. They are used as input for the sub-grid orography scheme which represents low-level blocking and orographic gravity wave effects.

The angle of the sub-grid scale orography characterises the geographical orientation of the terrain in the horizontal plane (from a bird's-eye view) relative to an eastwards axis.
radians  
slor 163 Slope of sub-gridscale orography This parameter is one of four parameters (the others being standard deviation, angle and anisotropy) that describe the features of the orography that are too small to be resolved by the model grid. These four parameters are calculated for orographic features with horizontal scales comprised between 5 km and the model grid resolution, being derived from the height of valleys, hills and mountains at about 1 km resolution. They are used as input for the sub-grid orography scheme which represents low-level blocking and orographic gravity wave effects.

This parameter represents the slope of the sub-grid valleys, hills and mountains. A flat surface has a value of 0, and a 45 degree slope has a value of 0.5.
~  
tcc 164 Total cloud cover This parameter is the proportion of a grid box covered by cloud. Total cloud cover is a single level field calculated from the cloud occurring at different model levels through the atmosphere. Assumptions are made about the degree of overlap/randomness between clouds at different heights.

Cloud fractions vary from 0 to 1.
(0 - 1)  
10u 165 10 metre U wind component This parameter is the eastward component of the 10m wind. It is the horizontal speed of air moving towards the east, at a height of ten metres above the surface of the Earth, in metres per second.

Care should be taken when comparing this parameter with observations, because wind observations vary on small space and time scales and are affected by the local terrain, vegetation and buildings that are represented only on average in the ECMWF Integrated Forecasting System.

This parameter can be combined with the V component of 10m wind to give the speed and direction of the horizontal 10m wind.
m s**-1  
10v 166 10 metre V wind component This parameter is the northward component of the 10m wind. It is the horizontal speed of air moving towards the north, at a height of ten metres above the surface of the Earth, in metres per second.

Care should be taken when comparing this parameter with observations, because wind observations vary on small space and time scales and are affected by the local terrain, vegetation and buildings that are represented only on average in the ECMWF Integrated Forecasting System.

This parameter can be combined with the U component of 10m wind to give the speed and direction of the horizontal 10m wind.
m s**-1  
2t 167 2 metre temperature This parameter is the temperature of air at 2m above the surface of land, sea or in-land waters.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
2d 168 2 metre dewpoint temperature This parameter is the temperature to which the air, at 2 metres above the surface of the Earth, would have to be cooled for saturation to occur.

It is a measure of the humidity of the air. Combined with temperature and pressure, it can be used to calculate the relative humidity.

2m dew point temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
stl2 170 Soil temperature level 2 This parameter is the temperature of the soil at level 2 (in the middle of layer 2).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
lsm 172 Land-sea mask This parameter is the proportion of land, as opposed to ocean or inland waters (lakes, reservoirs, rivers and coastal waters), in a grid box.
This parameter has values ranging between zero and one and is dimensionless.
In cycles of the ECMWF Integrated Forecasting System (IFS) from CY41R1 (introduced in May 2015) onwards, grid boxes where this parameter has a value above 0.5 can be comprised of a mixture of land and inland water but not ocean. Grid boxes with a value of 0.5 and below can only be comprised of a water surface. In the latter case, the lake cover is used to determine how much of the water surface is ocean or inland water.
In cycles of the IFS before CY41R1, grid boxes where this parameter has a value above 0.5 can only be comprised of land and those grid boxes with a value of 0.5 and below can only be comprised of ocean. In these older model cycles, there is no differentiation between ocean and inland water.
(0 - 1)  
al 174 Albedo This parameter is a measure of the reflectivity of the Earth's surface. It is the fraction of solar (shortwave) radiation reflected by Earth's surface, across the solar spectrum, for both direct and diffuse radiation.

This parameter is a climatological (observed values averaged over a period of several years) background albedo which varies through the year and which excludes values over snow and sea-ice. Over land, values are typically between about 0.1 and 0.4 and the ocean has low values of 0.1 or less.

Note: this parameter is a very old broadband albedo climatology that has since been replaced by a MODIS climatology in two spectral bands (see parameters 210186 to 210191).

Radiation from the Sun (also known as solar, or shortwave, radiation) is partly reflected back to space by clouds and particles in the atmosphere (aerosols) and some of it is absorbed. The rest is incident on the Earth's surface, where some of it is reflected. The portion that is reflected by the Earth's surface depends on the albedo. See further documentation.

This parameter is calculated as a fraction (0 - 1), but albedo is sometimes shown as a percentage (%).
(0 - 1)  
stl3 183 Soil temperature level 3 This parameter is the temperature of the soil at level 3 (in the middle of layer 3).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
lcc 186 Low cloud cover This parameter is the proportion of a grid box covered by cloud occurring in the lower levels of the troposphere. Low cloud is a single level field calculated from cloud occurring on model levels with a pressure greater than 0.8 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), low cloud would be calculated using levels with a pressure greater than 800 hPa (below approximately 2km (assuming a 'standard atmosphere')).

The low cloud cover parameter is calculated from cloud cover for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
mcc 187 Medium cloud cover This parameter is the proportion of a grid box covered by cloud occurring in the middle levels of the troposphere. Medium cloud is a single level field calculated from cloud occurring on model levels with a pressure between 0.45 and 0.8 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), medium cloud would be calculated using levels with a pressure of less than or equal to 800 hPa and greater than or equal to 450 hPa (between approximately 2km and 6km (assuming a 'standard atmosphere')).

The medium cloud parameter is calculated from cloud cover for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
hcc 188 High cloud cover The proportion of a grid box covered by cloud occurring in the high levels of the troposphere. High cloud is a single level field calculated from cloud occurring on model levels with a pressure less than 0.45 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), high cloud would be calculated using levels with a pressure of less than 450 hPa (approximately 6km and above ( assuming a `standard atmosphere`)).

The high cloud cover parameter is calculated from cloud for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
src 198 Skin reservoir content This parameter is the amount of water in the vegetation canopy and/or in a thin layer on the soil.

It represents the amount of rain intercepted by foliage, and water from dew. The maximum amount of 'skin reservoir content' a grid box can hold depends on the type of vegetation, and may be zero. Water leaves the 'skin reservoir' by evaporation.

See further information.
m of water equivalent  
tco3 206 Total column ozone This parameter is the total amount of ozone in a column of air extending from the surface of the Earth to the top of the atmosphere. This parameter can also be referred to as total ozone, or vertically integrated ozone. The values are dominated by ozone within the stratosphere.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation .

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

In the IFS, the units for total ozone are kilograms per square metre, but before 12/06/2001 dobson units were used. Dobson units (DU) are still used extensively for total column ozone. 1 DU = 2.1415E-5 kg m-2
kg m**-2  
iews 229 Instantaneous eastward turbulent surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the stress on the Earth's surface at the specified time in the eastward direction due to both the turbulent interactions between the atmosphere and the surface, and to turbulent orographic form drag.

The turbulent interactions between the atmosphere and the surface are due to the roughness of the surface.

The turbulent orographic form drag is the stress due to the valleys, hills and mountains on horizontal scales below 5km being derived from land surface data at about 1 km resolution. See further information.

Positive (negative) values denote stress in the eastward (westward) direction.
N m**-2  
inss 230 Instantaneous northward turbulent surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the stress on the Earth's surface at the specified time in the northward direction due to both the turbulent interactions between the atmosphere and the surface, and to turbulent orographic form drag.

The turbulent interactions between the atmosphere and the surface are due to the roughness of the surface.

The turbulent orographic form drag is the stress due to the valleys, hills and mountains on horizontal scales below 5km being derived from land surface data at about 1 km resolution. See further information.

Positive (negative) values denote stress in the northward (southward) direction.
N m**-2  
lsrh 234 Logarithm of surface roughness length for heat Represents surface roughness length for heat and moisture over land. Climatological field. ~  
skt 235 Skin temperature This parameter is the temperature of the surface of the Earth.

The skin temperature is the theoretical temperature that is required to satisfy the surface energy balance. It represents the temperature of the uppermost surface layer, which has no heat capacity and so can respond instantaneously to changes in surface fluxes. Skin temperature is calculated differently over land and sea.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information about the skin temperature over land and over sea.
K  
stl4 236 Soil temperature level 4 This parameter is the temperature of the soil at level 4 (in the middle of layer 4).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
tsn 238 Temperature of snow layer This parameter gives the temperature of the snow layer from the ground to the snow-air interface.

The ECMWF Integrated Forecast System (IFS) model represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box.

See further information on snow in the IFS.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
aluvpi 210186 UV visible albedo for direct radiation, isotropic component Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the isotropic component of the snow-free land-surface albedo for solar radiation with wavelength shorter than 0.7 µm (microns, 1 millionth of a metre).

In the ECMWF Integrated Forecasting System (IFS) albedo is dealt with separately for solar radiation with wavelengths greater/less than 0.7µm. Within each of these two bands, the dependence of the albedo of the snow-free land surface on solar zenith angle is parameterized using three coefficients: an isotropic component, a volumetric component and a geometric component. This leads to a total of six components. The IFS first uses them to compute the snow-free land-surface albedo to direct and diffuse downwelling solar radiation, and then modifies these albedos to account for water, ice and snow. Climatological (observed values averaged over a period of several years) values are used for these albedo components, which were taken from observations by the MODIS satellite instrument and vary from month to month through the year. See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).
(0 - 1)  
aluvpv 210187 UV visible albedo for direct radiation, volumetric component Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the volumetric component of the snow-free land-surface albedo for solar radiation with wavelength shorter than 0.7 µm (microns, 1 millionth of a metre).

In the ECMWF Integrated Forecasting System (IFS) albedo is dealt with separately for solar radiation with wavelengths greater/less than 0.7µm. Within each of these two bands, the dependence of the albedo of the snow-free land surface on solar zenith angle is parameterized using three coefficients: an isotropic component, a volumetric component and a geometric component. This leads to a total of six components. The IFS first uses them to compute the snow-free land-surface albedo to direct and diffuse downwelling solar radiation, and then modifies these albedos to account for water, ice and snow. Climatological (observed values averaged over a period of several years) values are used for these albedo components, which were taken from observations by the MODIS satellite instrument and vary from month to month through the year. See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).
(0 - 1)  
aluvpg 210188 UV visible albedo for direct radiation, geometric component Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the volumetric component of the snow-free land-surface albedo for solar radiation with wavelength shorter than 0.7 µm (microns, 1 millionth of a metre).

In the ECMWF Integrated Forecasting System (IFS) albedo is dealt with separately for solar radiation with wavelengths greater/less than 0.7µm. Within each of these two bands, the dependence of the albedo of the snow-free land surface on solar zenith angle is parameterized using three coefficients: an isotropic component, a volumetric component and a geometric component. This leads to a total of six components. The IFS first uses them to compute the snow-free land-surface albedo to direct and diffuse downwelling solar radiation, and then modifies these albedos to account for water, ice and snow. Climatological (observed values averaged over a period of several years) values are used for these albedo components, which were taken from observations by the MODIS satellite instrument and vary from month to month through the year. See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).
(0 - 1)  
alnipi 210189 Near IR albedo for direct radiation, isotropic component Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the isotropic component of the snow-free land-surface albedo for solar radiation with wavelength longer than 0.7 µm (microns, 1 millionth of a metre).

In the ECMWF Integrated Forecasting System (IFS) albedo is dealt with separately for solar radiation with wavelengths greater/less than 0.7µm. Within each of these two bands, the dependence of the albedo of the snow-free land surface on solar zenith angle is parameterized using three coefficients: an isotropic component, a volumetric component and a geometric component. This leads to a total of six components. The IFS first uses them to compute the snow-free land-surface albedo to direct and diffuse downwelling solar radiation, and then modifies these albedos to account for water, ice and snow. Climatological (observed values averaged over a period of several years) values are used for these albedo components, which were taken from observations by the MODIS satellite instrument and vary from month to month through the year. See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).
(0 - 1)  
alnipv 210190 Near IR albedo for direct radiation, volumetric component Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the volumetric component of the snow-free land-surface albedo for solar radiation with wavelength greater than 0.7 µm (microns, 1 millionth of a metre).

In the ECMWF Integrated Forecasting System (IFS) albedo is dealt with separately for solar radiation with wavelengths greater/less than 0.7µm. Within each of these two bands, the dependence of the albedo of the snow-free land surface on solar zenith angle is parameterized using three coefficients: an isotropic component, a volumetric component and a geometric component. This leads to a total of six components. The IFS first uses them to compute the snow-free land-surface albedo to direct and diffuse downwelling solar radiation, and then modifies these albedos to account for water, ice and snow. Climatological (observed values averaged over a period of several years) values are used for these albedo components, which vary from month to month through the year. See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).
(0 - 1)  
alnipg 210191 Near IR albedo for direct radiation, geometric component Albedo is a measure of the reflectivity of the Earth's surface. This parameter is the geometric component of the snow-free land-surface albedo for solar radiation with wavelength greater than 0.7 µm (microns, 1 millionth of a metre).

In the ECMWF Integrated Forecasting System (IFS) albedo is dealt with separately for solar radiation with wavelengths greater/less than 0.7µm. Within each of these two bands, the dependence of the albedo of the snow-free land surface on solar zenith angle is parameterized using three coefficients: an isotropic component, a volumetric component and a geometric component. This leads to a total of six components. The IFS first uses them to compute the snow-free land-surface albedo to direct and diffuse downwelling solar radiation, and then modifies these albedos to account for water, ice and snow. Climatological (observed values averaged over a period of several years) values are used for these albedo components, which vary from month to month through the year. See further documentation

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation).
(0 - 1)  
dl 228007 Lake total depth This parameter is the mean depth of inland water bodies (lakes, reservoirs and rivers) and coastal waters. This field is specified from in-situ measurements and indirect estimates and is constant in time.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
m  
lmlt 228008 Lake mix-layer temperature This parameter is the temperature of the uppermost layer of inland water bodies (lakes, reservoirs and rivers) or coastal waters, that is well mixed and has a near constant temperature with depth (i.e., a uniform distribution of temperature with depth).

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below. The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

Mixing within the mixed layer can occur when the density of the surface (and near-surface) water is greater than that of the water below. Mixing can also occur through the action of wind on the surface of the lake.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
lmld 228009 Lake mix-layer depth This parameter is the thickness of the uppermost layer of inland water bodies (lakes, reservoirs and rivers) or coastal waters, that is well mixed and has a near constant temperature with depth (i.e., a uniform distribution of temperature with depth).

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below, where temperature changes with depth. The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

Mixing within the mixed layer can occur when the density of the surface (and near-surface) water is greater than that of the water below. Mixing can also occur through the action of wind on the surface of the lake.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
m  
lblt 228010 Lake bottom temperature This parameter is the temperature of water at the bottom of inland water bodies (lakes, reservoirs, rivers) and coastal waters.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
ltlt 228011 Lake total layer temperature This parameter is the mean temperature of the total water column in inland water bodies (lakes, reservoirs and rivers) and coastal waters.

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below, where temperature changes with depth. This parameter is the mean over the two layers.

The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
lshf 228012 Lake shape factor This parameter describes the way that temperature changes with depth in the thermocline layer of inland water bodies (lakes, reservoirs and rivers) and coastal waters (i.e., it describes the shape of the vertical temperature profile). It is used to calculate the lake bottom temperature and other lake-related parameters.

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below, where temperature changes with depth. The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
dimensionless  
lict 228013 Lake ice surface temperature This parameter is the temperature of the uppermost surface of ice on inland water bodies (lakes, reservoirs, and rivers) and coastal waters. That is the temperature at the ice/atmosphere or ice/snow interface.

The ECMWF Integrated Forecasting System represents the formation and melting of ice on lakes. A single ice layer is represented.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
licd 228014 Lake ice total depth This parameter is the thickness of ice on inland water bodies (lakes, reservoirs and rivers) and coastal waters.

The ECMWF Integrated Forecasting System represents the formation and melting of ice on inland water bodies. A single ice layer is represented. This parameter is the thickness of that ice layer.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
m  
200u 228239 200 metre U wind component   m s**-1  
200v 228240 200 metre V wind component   m s**-1  
100u 228246 100 metre U wind component This parameter is the eastward component of the 100 m wind. It is the horizontal speed of air moving towards the east, at a height of 100 metres above the surface of the Earth, in metres per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.

This parameter can be combined with the northward component to give the speed and direction of the horizontal 100 m wind.
m s**-1  
100v 228247 100 metre V wind component This parameter is the northward component of the 100 m wind. It is the horizontal speed of air moving towards the north, at a height of 100 metres above the surface of the Earth, in metres per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.

This parameter can be combined with the eastward component to give the speed and direction of the horizontal 100 m wind.
m s**-1  

I-i-a: Atmospheric fields -single level - forecast

Single level -forecast

  Forecast time step Base time
T+0 to T+90 Hourly     00 UTC, 06 UTC, 12 UTC and 18 UTC
 T+93 to T+144 3-hourly 00 UTC and 12 UTC
T+150h to T+240h 6-hourly 00 UTC and 12 UTC
Short Name ID Long Name Description Units Additional information
sro 8 Surface runoff Some water from rainfall, melting snow, or deep in the soil, stays stored in the soil. Otherwise, the water drains away, either over the surface (surface runoff), or under the ground (sub-surface runoff) and the sum of these two is simply called 'runoff'. This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted.The units of runoff are depth in metres. This is the depth the water would have if it were spread evenly over the grid box. Care should be taken when comparing model parameters with observations, because observations are often local to a particular point rather than averaged over a grid square area. Observations are also often taken in different units, such as mm/day, rather than the accumulated metres produced here.

Runoff is a measure of the availability of water in the soil, and can, for example, be used as an indicator of drought or flood. More information about how runoff is calculated is given in the IFS Physical Processes documentation.
m  
ssro 9 Sub-surface runoff Some water from rainfall, melting snow, or deep in the soil, stays stored in the soil. Otherwise, the water drains away, either over the surface (surface runoff), or under the ground (sub-surface runoff) and the sum of these two is simply called 'runoff'. This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted.The units of runoff are depth in metres. This is the depth the water would have if it were spread evenly over the grid box. Care should be taken when comparing model parameters with observations, because observations are often local to a particular point rather than averaged over a grid square area. Observations are also often taken in different units, such as mm/day, rather than the accumulated metres produced here.

Runoff is a measure of the availability of water in the soil, and can, for example, be used as an indicator of drought or flood. More information about how runoff is calculated is given in the IFS Physical Processes documentation.
m  
parcs 20 Clear sky surface photosynthetically active radiation 0.44-0.70 um accumulated field J m**-2  
cl 26 Lake cover This parameter is the proportion of a grid box covered by inland water bodies (lakes, reservoirs, rivers) and coastal waters. Values vary between 0: no inland or coastal water body, and 1: grid box is fully covered with inland or coastal water body. This field is specified from observations and is constant in time.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
(0 - 1)  
ci 31 Sea ice area fraction This parameter is the fraction of a grid box which is covered by sea ice. Sea ice can only occur in a grid box which includes ocean or inland water according to the land sea mask and lake cover, at the resolution being used. This parameter can be known as sea-ice (area) fraction, sea-ice concentration and more generally as sea-ice cover.

Coupled atmosphere ocean simulations of the ECMWF Integrated Forecasting System (IFS) predict the formation and melting of sea ice. Otherwise, in analyses and atmosphere only simulations, sea ice is derived from observations, but the model does take account of the way that sea ice alters the interaction between the atmosphere and ocean.

Sea ice is frozen sea water which floats on the surface of the ocean. Sea ice does not include ice which forms on land such as glaciers, icebergs and ice-sheets. It also excludes ice shelves which are anchored on land, but protrude out over the surface of the ocean. These phenomena are not modelled by the IFS.

Long-term monitoring of sea ice is important for understanding climate change. Sea ice also affects shipping routes through the polar regions.
(0 - 1)  
asn 32 Snow albedo This parameter is a measure of the reflectivity of the snow-covered part of the grid box. It is the fraction of solar (shortwave) radiation reflected by snow across the solar spectrum.

The ECMWF Integrated Forecast System represents snow as a single additional layer over the uppermost soil level.

This parameter changes with snow age and also depends on vegetation height. For low vegetation, it ranges between 0.52 for old snow and 0.88 for fresh snow. For high vegetation with snow underneath, it depends on vegetation type and has values between 0.27 and 0.38. See further information.
(0 - 1)  
rsn 33 Snow density This parameter is the mass of snow per cubic metre in the snow layer.

The ECMWF Integrated Forecast System (IFS) model represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box.

See further information on snow in the IFS.
kg m**-3  
sst 34 Sea surface temperature This parameter is the temperature of sea water near the surface.

This parameter is taken from various providers, who process the observational data in different ways. Each provider uses data from several different observational sources. For example, satellites measure sea surface temperature (SST) in a layer a few microns thick in the uppermost mm of the ocean, drifting buoys measure SST at a depth of about 0.2-1.5m, whereas ships sample sea water down to about 10m, while the vessel is underway. Deeper measurements are not affected by changes that occur during a day, due to the rising and setting of the Sun (diurnal variations).

Sometimes this parameter is taken from a forecast made by coupling the NEMO ocean model to the ECMWF Integrated Forecasting System. In this case, the SST is the average temperature of the uppermost metre of the ocean and does exhibit diurnal variations.

See further documentation .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
istl1 35 Ice temperature layer 1 This parameter is the sea-ice temperature in layer 1 (0 to 7cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
istl2 36 Ice temperature layer 2 This parameter is the sea-ice temperature in layer 2 (7 to 28 cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
istl3 37 Ice temperature layer 3 This parameter is the sea-ice temperature in layer 3 (28 to 100 cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
istl4 38 Ice temperature layer 4 This parameter is the sea-ice temperature in layer 4 (100 to 150 cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:
Layer 1: 0-7cm
Layer 2: 7-28cm
Layer 3: 28-100cm
Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below. See further documentation.
K  
swvl1 39 Volumetric soil water layer 1 This parameter is the volume of water in soil layer 1 (0 - 7cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl2 40 Volumetric soil water layer 2 This parameter is the volume of water in soil layer 2 (7 - 28cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl3 41 Volumetric soil water layer 3 This parameter is the volume of water in soil layer 3 (28 - 100cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl4 42 Volumetric soil water layer 4 This parameter is the volume of water in soil layer 4 (100 - 289cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
es 44 Snow evaporation This parameter is the accumulated amount of water that has evaporated from snow from the snow-covered area of a grid box into vapour in the air above.

The ECMWF Integrated Forecast System represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box. This parameter is the depth of water there would be if the evaporated snow (from the snow-covered area of a grid box ) were liquid and were spread evenly over the whole grid box.

This parameter is accumulated over a  particular time period which depends on the data extracted.

The ECMWF Integrated Forecasting System convention is that downward fluxes are positive. Therefore, negative values indicate evaporation and positive values indicate deposition.
m of water equivalent  
smlt 45 Snowmelt This parameter is the accumulated amount of water that has melted from snow in the snow-covered area of a grid box.

The ECMWF Integrated Forecast System represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box. This parameter is the depth of water there would be if the melted snow (from the snow-covered area of a grid box ) were spread evenly over the whole grid box. For example, if half the grid box were covered in snow with a water equivalent depth of 0.02m, this parameter would have a value of 0.01m.

This parameter is accumulated over a  particular time period which depends on the data extracted.
m of water equivalent  
dsrp 47 Direct solar radiation This parameter is the amount of direct radiation from the Sun (also known as solar or shortwave radiation) reaching the surface on a plane perpendicular to the direction of the Sun.

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation). See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
10fg 49 10 metre wind gust since previous post-processing Maximum 3 second wind at 10 m height as defined by WMO.

Parametrization represents turbulence only before 01102008; thereafter effects of convection are included. The 3 s gust is computed every time step and and the maximum is kept since the last postprocessing.
m s**-1  
lspf 50 Large-scale precipitation fraction This parameter is the accumulation of the fraction of the grid box (0-1) that was covered by large-scale precipitation.

This parameter is accumulated over a particular time period which depends on the data extracted. See further information.
s  
uvb 57 Downward UV radiation at the surface This parameter is the amount of ultraviolet (UV) radiation reaching the surface. It is the amount of radiation passing through a horizontal plane, not a plane perpendicular to the direction of the Sun.

UV radiation is part of the electromagnetic spectrum emitted by the Sun that has wavelengths shorter than visible light. In the ECMWF Integrated Forecasting system it is defined as radiation with a wavelength of 0.20-0.44 µm (microns, 1 millionth of a metre).

Small amounts of UV are essential for living organisms, but overexposure may result in cell damage; in humans this includes acute and chronic health effects on the skin, eyes and immune system. UV radiation is absorbed by the ozone layer, but some reaches the surface. The depletion of the ozone layer is causing concern over an increase in the damaging effects of UV.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
par 58 Photosynthetically active radiation at the surface 0.40-0.70 um. Accumulated field.
Before Cycle 43R1, a coding error meant that PAR was computed from the wrong spectral bands and hence was underestimated by around 30%.
It should therefore only be used from Cycles 43R1 and later.
J m**-2  
cape 59 Convective available potential energy This is an indication of the instability (or stability) of the atmosphere and can be used to assess the potential for the development of convection, which can lead to heavy rainfall, thunderstorms and other severe weather.

In the ECMWF Integrated Forecasting System (IFS), CAPE is calculated by considering parcels of air departing at different model levels below the 350 hPa level. If a parcel of air is more buoyant (warmer and/or with more moisture) than its surrounding environment, it will continue to rise (cooling as it rises) until it reaches a point where it no longer has positive buoyancy. CAPE is the potential energy represented by the total excess buoyancy. The maximum CAPE produced by the different parcels is the value retained.

Large positive values of CAPE indicate that an air parcel would be much warmer than its surrounding environment and therefore, very buoyant. CAPE is related to the maximum potential vertical velocity of air within an updraft; thus, higher values indicate greater potential for severe weather. Observed values in thunderstorm environments often may exceed 1000 joules per kilogram (J kg-1), and in extreme cases may exceed 5000 J kg-1.

The calculation of this parameter assumes: (i) the parcel of air does not mix with surrounding air; (ii) ascent is pseudo-adiabatic (all condensed water falls out) and (iii) other simplifications related to the mixed-phase condensational heating.
J kg**-1  
lai_lv 66 Leaf area index, low vegetation This parameter is the surface area of one side of all the leaves found over an area of land for vegetation classified as 'low'. This parameter has a value of 0 over bare ground or where there are no leaves. It can be calculated daily from satellite data. It is important for forecasting, for example, how much rainwater will be intercepted by the vegetative canopy, rather than falling to the ground.

This is one of the parameters in the model that describes land surface vegetation. 'Low vegetation' consists of crops and mixed farming, irrigated crops, short grass, tall grass, tundra, semidesert, bogs and marshes, evergreen shrubs, deciduous shrubs, and water and land mixtures.
m**2 m**-2  
lai_hv 67 Leaf area index, high vegetation This parameter is the surface area of one side of all the leaves found over an area of land for vegetation classified as 'high'. This parameter has a value of 0 over bare ground or where there are no leaves. It can be calculated daily from satellite data. It is important for forecasting, for example, how much rainwater will be intercepted by the vegetative canopy, rather than falling to the ground.

This is one of the parameters in the model that describes land surface vegetation. 'High vegetation' consists of evergreen trees, deciduous trees, mixed forest/woodland, and interrupted forest.
m**2 m**-2  
tclw 78 Total column cloud liquid water This parameter is the amount of liquid water contained within cloud droplets in a column extending from the surface of the Earth to the top of the atmosphere. Rain water droplets, which are much larger in size (and mass), are not included in this parameter.

This parameter represents the area averaged value for a model grid box.

Clouds contain a continuum of different- sized water droplets and ice particles. The ECMWF Integrated Forecasting System (IFS) cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, phase transition and aggregation are also highly simplified in the IFS.
kg m**-2  
tciw 79 Total column cloud ice water This parameter is the amount of ice contained within clouds in a column extending from the surface of the Earth to the top of the atmosphere. Snow (aggregated ice crystals) is not included in this parameter.

This parameter represents the area averaged value for a model grid box.

Clouds contain a continuum of different- sized water droplets and ice particles. The ECMWF Integrated Forecasting System (IFS) cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, phase transition and aggregation are also highly simplified in the IFS.
kg m**-2  
mx2t6 121 Maximum temperature at 2 metres in the last 6 hours The highest value of 2 metre temperature in the previous 6 hour period.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
mn2t6 122 Minimum temperature at 2 metres in the last 6 hours The lowest value of 2 metre temperature in the previous 6 hour period.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
10fg6 123 10 metre wind gust in the last 6 hours This parameter is the maximum wind gust in the last 6 hours at a height of ten metres above the surface of the Earth.

The WMO defines a wind gust as the maximum of the wind averaged over 3 second intervals. This duration is shorter than a model time step, and so the ECMWF Integrated Forecasting System deduces the magnitude of a gust within each time step from the time-step-averaged surface stress, surface friction, wind shear and stability. Then, the maximum wind gust is selected from the gusts at each time step during the last 6 hours.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
m s**-1  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
sp 134 Surface pressure This parameter is the pressure (force per unit area) of the atmosphere on the surface of land, sea and in-land water.

It is a measure of the weight of all the air in a column vertically above the area of the Earth's surface represented at a fixed point.

Surface pressure is often used in combination with temperature to calculate air density.

The strong variation of pressure with altitude makes it difficult to see the low and high pressure systems over mountainous areas, so mean sea level pressure, rather than surface pressure, is normally used for this purpose.

The units of this parameter are Pascals (Pa). Surface pressure is often measured in hPa and sometimes is presented in the old units of millibars, mb (1 hPa = 1 mb= 100 Pa).
Pa  
tcw 136 Total column water This parameter is the sum of water vapour, liquid water, cloud ice, rain and snow in a column extending from the surface of the Earth to the top of the atmosphere. In old versions of the ECMWF model (IFS), rain and snow were not accounted for. kg m**-2  
tcwv 137 Total column water vapour This parameter is the total amount of water vapour in a column extending from the surface of the Earth to the top of the atmosphere.

This parameter represents the area averaged value for a grid box.
kg m**-2  
stl1 139 Soil temperature level 1 This parameter is the temperature of the soil at level 1 (in the middle of layer 1).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
sd 141 Snow depth This parameter is the depth of snow from the snow-covered area of a grid box.

Its units are metres of water equivalent, so it is the depth the water would have if the snow melted and was spread evenly over the whole grid box. The ECMWF Integrated Forecast System represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box.

See further information.
m of water equivalent  
lsp 142 Large-scale precipitation This parameter is the accumulated liquid and frozen water, comprising rain and snow, that falls to the Earth's surface and which is generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of the grid box or larger. Precipitation can also be generated by the convection scheme in the IFS, which represents convection at spatial scales smaller than the grid box. See further information. This parameter does not include fog, dew or the precipitation that evaporates in the atmosphere before it lands at the surface of the Earth.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m  
cp 143 Convective precipitation This parameter is the accumulated liquid and frozen water, comprising rain and snow, that falls to the Earth's surface and which is generated by the convection scheme in the ECMWF Integrated Forecasting System (IFS). The convection scheme represents convection at spatial scales smaller than the grid box. Precipitation can also be generated by the cloud scheme in the IFS, which represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly at spatial scales of the grid box or larger. See further information. This parameter does not include fog, dew or the precipitation that evaporates in the atmosphere before it lands at the surface of the Earth.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m  
sf 144 Snowfall This parameter is the accumulated snow that falls to the Earth's surface. It is the sum of large-scale snowfall and convective snowfall. Large-scale snowfall is generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of the grid box or larger. Convective snowfall is generated by the convection scheme in the IFS, which represents convection at spatial scales smaller than the grid box. See further information.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m of water equivalent  
bld 145 Boundary layer dissipation This parameter is the amount of energy per unit area that is converted from kinetic energy, into heat, due to small-scale motion in the lower levels of the atmosphere. These small-scale motions are called eddies or turbulence. A higher value of this parameter means that more energy is being converted to heat, and so the mean flow is slowing more and the air temperature is rising by a greater amount.

This parameter is accumulated over a particular time period which depends on the data extracted.
J m**-2  
sshf 146 Surface sensible heat flux This parameter is the transfer of heat between the Earth's surface and the atmosphere through the effects of turbulent air motion (but excluding any heat transfer resulting from condensation or evaporation).

The magnitude of the sensible heat flux is governed by the difference in temperature between the surface and the overlying atmosphere, wind speed and the surface roughness. For example, cold air overlying a warm surface would produce a sensible heat flux from the land (or ocean) into the atmosphere. See further documentation

This is a single level parameter and it is accumulated over a particular time period which depends on the data extracted.The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds. The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
slhf 147 Surface latent heat flux This parameter is the transfer of latent heat (resulting from water phase changes, such as evaporation or condensation) between the Earth's surface and the atmosphere through the effects of turbulent air motion. Evaporation from the Earth's surface represents a transfer of energy from the surface to the atmosphere. See further documentation

This parameter is accumulated over a particular time period which depends on the data extracted.The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
chnk 148 Charnock This parameter accounts for increased aerodynamic roughness as wave heights grow due to increasing surface stress. It depends on the wind speed, wave age and other aspects of the sea state and is used to calculate how much the waves slow down the wind.

When the atmospheric model is run without the ocean model, this parameter has a constant value of 0.018. When the atmospheric model is coupled to the ocean model, this parameter is calculated by the ECMWF Wave Model.
~  
msl 151 Mean sea level pressure This parameter is the pressure (force per unit area) of the atmosphere adjusted to the height of mean sea level.

It is a measure of the weight that all the air in a column vertically above the area of Earth's surface would have at that point, if the point were located at the mean sea level. It is calculated over all surfaces - land, sea and in-land water.

Maps of mean sea level pressure are used to identify the locations of low and high pressure systems, often referred to as cyclones and anticyclones. Contours of mean sea level pressure also indicate the strength of the wind. Tightly packed contours show stronger winds.

The units of this parameter are pascals (Pa). Mean sea level pressure is often measured in hPa and sometimes is presented in the old units of millibars, mb (1 hPa = 1 mb = 100 Pa).
Pa  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
blh 159 Boundary layer height This parameter is the depth of air next to the Earth's surface which is most affected by the resistance to the transfer of momentum, heat or moisture across the surface.

The boundary layer height can be as low as a few tens of metres, such as in cooling air at night, or as high as several kilometres over the desert in the middle of a hot sunny day. When the boundary layer height is low, higher concentrations of pollutants (emitted from the Earth's surface) can develop.

The boundary layer height calculation is based on the bulk Richardson number (a measure of the atmospheric conditions) following the conclusions of a 2012 review. See further information.
m  
tcc 164 Total cloud cover This parameter is the proportion of a grid box covered by cloud. Total cloud cover is a single level field calculated from the cloud occurring at different model levels through the atmosphere. Assumptions are made about the degree of overlap/randomness between clouds at different heights.

Cloud fractions vary from 0 to 1.
(0 - 1)  
10u 165 10 metre U wind component This parameter is the eastward component of the 10m wind. It is the horizontal speed of air moving towards the east, at a height of ten metres above the surface of the Earth, in metres per second.

Care should be taken when comparing this parameter with observations, because wind observations vary on small space and time scales and are affected by the local terrain, vegetation and buildings that are represented only on average in the ECMWF Integrated Forecasting System.

This parameter can be combined with the V component of 10m wind to give the speed and direction of the horizontal 10m wind.
m s**-1  
10v 166 10 metre V wind component This parameter is the northward component of the 10m wind. It is the horizontal speed of air moving towards the north, at a height of ten metres above the surface of the Earth, in metres per second.

Care should be taken when comparing this parameter with observations, because wind observations vary on small space and time scales and are affected by the local terrain, vegetation and buildings that are represented only on average in the ECMWF Integrated Forecasting System.

This parameter can be combined with the U component of 10m wind to give the speed and direction of the horizontal 10m wind.
m s**-1  
2t 167 2 metre temperature This parameter is the temperature of air at 2m above the surface of land, sea or in-land waters.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
2d 168 2 metre dewpoint temperature This parameter is the temperature to which the air, at 2 metres above the surface of the Earth, would have to be cooled for saturation to occur.

It is a measure of the humidity of the air. Combined with temperature and pressure, it can be used to calculate the relative humidity.

2m dew point temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
ssrd 169 Surface solar radiation downwards This parameter is the amount of solar radiation (also known as shortwave radiation) that reaches a horizontal plane at the surface of the Earth. This parameter comprises both direct and diffuse solar radiation.

Radiation from the Sun (solar, or shortwave, radiation) is partly reflected back to space by clouds and particles in the atmosphere (aerosols) and some of it is absorbed. The rest is incident on the Earth's surface (represented by this parameter). See further documentation.

To a reasonably good approximation, this parameter is the model equivalent of what would be measured by a pyranometer (an instrument used for measuring solar radiation) at the surface. However, care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds. The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
stl2 170 Soil temperature level 2 This parameter is the temperature of the soil at level 2 (in the middle of layer 2).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
lsm 172 Land-sea mask This parameter is the proportion of land, as opposed to ocean or inland waters (lakes, reservoirs, rivers and coastal waters), in a grid box.
This parameter has values ranging between zero and one and is dimensionless.
In cycles of the ECMWF Integrated Forecasting System (IFS) from CY41R1 (introduced in May 2015) onwards, grid boxes where this parameter has a value above 0.5 can be comprised of a mixture of land and inland water but not ocean. Grid boxes with a value of 0.5 and below can only be comprised of a water surface. In the latter case, the lake cover is used to determine how much of the water surface is ocean or inland water.
In cycles of the IFS before CY41R1, grid boxes where this parameter has a value above 0.5 can only be comprised of land and those grid boxes with a value of 0.5 and below can only be comprised of ocean. In these older model cycles, there is no differentiation between ocean and inland water.
(0 - 1)  
strd 175 Surface thermal radiation downwards This parameter is the amount of thermal (also known as longwave or terrestrial) radiation emitted by the atmosphere and clouds that reaches a horizontal plane at the surface of the Earth.

The surface of the Earth emits thermal radiation, some of which is absorbed by the atmosphere and clouds. The atmosphere and clouds likewise emit thermal radiation in all directions, some of which reaches the surface (represented by this parameter). See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds. The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
ssr 176 Surface net solar radiation This parameter is the amount of solar radiation (also known as shortwave radiation) that reaches a horizontal plane at the surface of the Earth (both direct and diffuse) minus the amount reflected by the Earth's surface (which is governed by the albedo).

Radiation from the Sun (solar, or shortwave, radiation) is partly reflected back to space by clouds and particles in the atmosphere (aerosols) and some of it is absorbed. The remainder is incident on the Earth's surface, where some of it is reflected. See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds. The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
str 177 Surface net thermal radiation Thermal radiation (also known as longwave or terrestrial radiation) refers to radiation emitted by the atmosphere, clouds and the surface of the Earth. This parameter is the difference between downward and upward thermal radiation at the surface of the Earth. It the amount passing through a horizontal plane.

The atmosphere and clouds emit thermal radiation in all directions, some of which reaches the surface as downward thermal radiation. The upward thermal radiation at the surface consists of thermal radiation emitted by the surface plus the fraction of downwards thermal radiation reflected upward by the surface. See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
tsr 178 Top net solar radiation This parameter is the incoming solar radiation (also known as shortwave radiation) minus the outgoing solar radiation at the top of the atmosphere. It is the amount of radiation passing through a horizontal plane. The incoming solar radiation is the amount received from the Sun. The outgoing solar radiation is the amount reflected and scattered by the Earth's atmosphere and surface. See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
ttr 179 Top net thermal radiation The thermal (also known as terrestrial or longwave) radiation emitted to space at the top of the atmosphere is commonly known as the Outgoing Longwave Radiation (OLR). The top net thermal radiation (this parameter) is equal to the negative of OLR. See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
ewss 180 Eastward turbulent surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the accumulated stress on the Earth's surface in the eastward direction due to both the turbulent interactions between the atmosphere and the surface, and to turbulent orographic form drag. The turbulent interactions between the atmosphere and the surface are due to the roughness of the surface. The turbulent orographic form drag is the stress due to the valleys, hills and mountains on horizontal scales below 5km being derived from land surface data at about 1 km resolution. See further information.

Positive (negative) values denote stress in the eastward (westward) direction.

This parameter is accumulated over a particular time period which depends on the data extracted.
N m**-2 s  
nsss 181 Northward turbulent surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the accumulated stress on the Earth's surface in the northward direction due to both the turbulent interactions between the atmosphere and the surface, and to turbulent orographic form drag.

The turbulent interactions between the atmosphere and the surface are due to the roughness of the surface.

The turbulent orographic form drag is the stress due to the valleys, hills and mountains on horizontal scales below 5km being derived from land surface data at about 1 km resolution. See further information.

Positive (negative) values denote stress in the northward (southward) direction.

This parameter is accumulated over a particular time period which depends on the data extracted.
N m**-2 s  
e 182 Evaporation This parameter is the accumulated amount of water that has evaporated from the Earth's surface, including a simplified representation of transpiration (from vegetation), into vapour in the air above.

This parameter is accumulated over a particular time period which depends on the data extracted.

The ECMWF Integrated Forecasting System convention is that downward fluxes are positive. Therefore, negative values indicate evaporation and positive values indicate condensation.
m of water equivalent  
stl3 183 Soil temperature level 3 This parameter is the temperature of the soil at level 3 (in the middle of layer 3).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
lcc 186 Low cloud cover This parameter is the proportion of a grid box covered by cloud occurring in the lower levels of the troposphere. Low cloud is a single level field calculated from cloud occurring on model levels with a pressure greater than 0.8 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), low cloud would be calculated using levels with a pressure greater than 800 hPa (below approximately 2km (assuming a 'standard atmosphere')).

The low cloud cover parameter is calculated from cloud cover for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
mcc 187 Medium cloud cover This parameter is the proportion of a grid box covered by cloud occurring in the middle levels of the troposphere. Medium cloud is a single level field calculated from cloud occurring on model levels with a pressure between 0.45 and 0.8 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), medium cloud would be calculated using levels with a pressure of less than or equal to 800 hPa and greater than or equal to 450 hPa (between approximately 2km and 6km (assuming a 'standard atmosphere')).

The medium cloud parameter is calculated from cloud cover for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
hcc 188 High cloud cover The proportion of a grid box covered by cloud occurring in the high levels of the troposphere. High cloud is a single level field calculated from cloud occurring on model levels with a pressure less than 0.45 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), high cloud would be calculated using levels with a pressure of less than 450 hPa (approximately 6km and above ( assuming a `standard atmosphere`)).

The high cloud cover parameter is calculated from cloud for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
sund 189 Sunshine duration This parameter is the length of time in which the direct solar (shortwave) radiation at the Earth's surface, falling on a plane perpendicular to the direction of the Sun, is greater than or equal to 120 W m-2.

The minimum solar intensity level of 120 W m-2 is defined by the World Meteorological Organisation and is consistent with observed values of sunshine duration from a Campbell-Stokes recorder (sometimes called a Stokes sphere) that can only measure moderately intense sunlight and brighter.

This parameter is accumulated over a particular time period which depends on the data extracted.
s  
lgws 195 Eastward gravity wave surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the component of the surface stress, in an eastward direction, associated with low-level blocking and orographic gravity waves. It is calculated by the ECMWF Integrated Forecasting System sub-grid orography scheme. It represents surface stress due to unresolved valleys, hills and mountains with horizontal scales between 5 km and the model grid. (The surface stress associated with orographic features with horizontal scales smaller than 5 km is accounted for by the turbulent orographic form drag scheme).

Orographic gravity waves are oscillations in the flow maintained by the buoyancy of displaced air parcels, produced when the air is deflected upwards by hills and mountains. Hills and mountains can also block the flow of air at low levels. Together these processes can create a drag or stress on the atmosphere at the Earth's surface (and at other levels in the atmosphere).

This parameter is accumulated over a particular time period which depends on the data extracted.
N m**-2 s  
mgws 196 Northward gravity wave surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the component of the surface stress, in a northward direction, associated with low-level blocking and orographic gravity waves. It is calculated by the ECMWF Integrated Forecasting System sub-grid orography scheme. It represents surface stress due to unresolved valleys, hills and mountains with horizontal scales between 5 km and the model grid. (The surface stress associated with orographic features with horizontal scales smaller than 5 km is accounted for by the turbulent orographic form drag scheme). The stress computed in the sub-grid orography scheme is associated with low-level blocking and orographic gravity waves.

Orographic gravity waves are oscillations in the flow maintained by the buoyancy of displaced air parcels, produced when the air is deflected upwards by hills and mountains. Hills and mountains can also block the flow of air at low levels. Together these processes can create a drag or stress on the atmosphere at the Earth's surface (and at other levels in the atmosphere).

This parameter is accumulated over a particular time period which depends on the data extracted.
N m**-2 s  
gwd 197 Gravity wave dissipation This parameter is the amount of energy per unit area that is converted from kinetic energy in the mean flow, into heat, due to the effects of orographic gravity waves. A higher value of this parameter means that more energy is being converted to heat, and so the mean flow is slowing more and the air temperature is rising by a greater amount.

Orographic gravity waves are oscillations in the flow maintained by the buoyancy of displaced air parcels, produced when the air is deflected upwards by hills and mountains. Hills and mountains can also block the flow of air at low levels. Together these processes can create a drag or stress on the atmosphere at the Earth's surface (and at other levels in the atmosphere).

This parameter is accumulated over a particular time period which depends on the data extracted.
J m**-2  
src 198 Skin reservoir content This parameter is the amount of water in the vegetation canopy and/or in a thin layer on the soil.

It represents the amount of rain intercepted by foliage, and water from dew. The maximum amount of 'skin reservoir content' a grid box can hold depends on the type of vegetation, and may be zero. Water leaves the 'skin reservoir' by evaporation.

See further information.
m of water equivalent  
mx2t 201 Maximum temperature at 2 metres since previous post-processing This parameter is the highest temperature of air at 2m above the surface of land, sea or in-land waters since the parameter was last archived in a particular forecast.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
mn2t 202 Minimum temperature at 2 metres since previous post-processing This parameter is the lowest temperature of air at 2m above the surface of land, sea or in-land waters since the parameter was last archived in a particular forecast.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
ro 205 Runoff Some water from rainfall, melting snow, or deep in the soil, stays stored in the soil. Otherwise, the water drains away, either over the surface (surface runoff), or under the ground (sub-surface runoff) and the sum of these two is simply called 'runoff'. This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted.The units of runoff are depth in metres. This is the depth the water would have if it were spread evenly over the grid box. Care should be taken when comparing model parameters with observations, because observations are often local to a particular point rather than averaged over a grid square area. Observations are also often taken in different units, such as mm/day, rather than the accumulated metres produced here.

Runoff is a measure of the availability of water in the soil, and can, for example, be used as an indicator of drought or flood. More information about how runoff is calculated is given in the IFS Physical Processes documentation.
m  
tco3 206 Total column ozone This parameter is the total amount of ozone in a column of air extending from the surface of the Earth to the top of the atmosphere. This parameter can also be referred to as total ozone, or vertically integrated ozone. The values are dominated by ozone within the stratosphere.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation .

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

In the IFS, the units for total ozone are kilograms per square metre, but before 12/06/2001 dobson units were used. Dobson units (DU) are still used extensively for total column ozone. 1 DU = 2.1415E-5 kg m-2
kg m**-2  
tsrc 208 Top net solar radiation, clear sky This parameter is the incoming solar radiation (also known as shortwave radiation) minus the outgoing solar radiation at the top of the atmosphere, assuming clear-sky (cloudless) conditions. It is the amount of radiation passing through a horizontal plane. The incoming solar radiation is the amount received from the Sun. The outgoing solar radiation is the amount reflected and scattered by the Earth's atmosphere and surface, assuming clear-sky (cloudless) conditions. See further documentation.

Clear-sky radiation quantities are computed for exactly the same atmospheric conditions of temperature, humidity, ozone, trace gases and aerosol as the total-sky (clouds included) quantities, but assuming that the clouds are not there.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
ttrc 209 Top net thermal radiation, clear sky This parameter is the thermal (also known as terrestrial or longwave) radiation emitted to space at the top of the atmosphere, assuming clear-sky (cloudless) conditions. It is the amount passing through a horizontal plane. Note that the ECMWF convention for vertical fluxes is positive downwards, so a flux from the atmosphere to space will be negative. See further documentation.

Clear-sky radiation quantities are computed for exactly the same atmospheric conditions of temperature, humidity, ozone, trace gases and aerosol as total-sky quantities (clouds included), but assuming that the clouds are not there.

The thermal radiation emitted to space at the top of the atmosphere is commonly known as the Outgoing Longwave Radiation (OLR) (i.e., taking a flux from the atmosphere to space as positive). Note that OLR is typically shown in units of watts per square metre (W m-2).

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.
J m**-2  
ssrc 210 Surface net solar radiation, clear sky This parameter is the amount of solar (shortwave) radiation reaching the surface of the Earth (both direct and diffuse) minus the amount reflected by the Earth's surface (which is governed by the albedo), assuming clear-sky (cloudless) conditions. It is the amount of radiation passing through a horizontal plane, not a plane perpendicular to the direction of the Sun.

Clear-sky radiation quantities are computed for exactly the same atmospheric conditions of temperature, humidity, ozone, trace gases and aerosol as the corresponding total-sky quantities (clouds included), but assuming that the clouds are not there.

Radiation from the Sun (solar, or shortwave, radiation) is partly reflected back to space by clouds and particles in the atmosphere (aerosols) and some of it is absorbed. The rest is incident on the Earth's surface, where some of it is reflected. The difference between downward and reflected solar radiation is the surface net solar radiation. See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
strc 211 Surface net thermal radiation, clear sky Thermal radiation (also known as longwave or terrestrial radiation) refers to radiation emitted by the atmosphere, clouds and the surface of the Earth. This parameter is the difference between downward and upward thermal radiation at the surface of the Earth, assuming clear-sky (cloudless) conditions. It is the amount of radiation passing through a horizontal plane. See further documentation.

Clear-sky radiation quantities are computed for exactly the same atmospheric conditions of temperature, humidity, ozone, trace gases and aerosol as the corresponding total-sky quantities (clouds included), but assuming that the clouds are not there.

The atmosphere and clouds emit thermal radiation in all directions, some of which reaches the surface as downward thermal radiation. The upward thermal radiation at the surface consists of thermal radiation emitted by the surface plus the fraction of downwards thermal radiation reflected upward by the surface. See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
tisr 212 TOA incident solar radiation Accumulated field J m**-2  
vimd 213 Vertically integrated moisture divergence The vertical integral of the moisture flux is the horizontal rate of flow of moisture (water vapour, cloud liquid and cloud ice), per metre across the flow, for a column of air extending from the surface of the Earth to the top of the atmosphere. Its horizontal divergence is the rate of moisture spreading outward from a point, per square metre.

This parameter is accumulated over a particular time period which depends on the data extracted

This parameter is positive for moisture that is spreading out, or diverging, and negative for the opposite, for moisture that is concentrating, or converging (convergence). This parameter thus indicates whether atmospheric motions act to decrease (for divergence) or increase (for convergence) the vertical integral of moisture, over the time period. High negative values of this parameter (i.e. large moisture convergence) can be related to precipitation intensification and floods.

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm.
kg m**-2  
tp 228 Total precipitation This parameter is the accumulated liquid and frozen water, comprising rain and snow, that falls to the Earth's surface. It is the sum of large-scale precipitation and convective precipitation. Large-scale precipitation is generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of the grid box or larger. Convective precipitation is generated by the convection scheme in the IFS, which represents convection at spatial scales smaller than the grid box. See further information. This parameter does not include fog, dew or the precipitation that evaporates in the atmosphere before it lands at the surface of the Earth.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m  
iews 229 Instantaneous eastward turbulent surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the stress on the Earth's surface at the specified time in the eastward direction due to both the turbulent interactions between the atmosphere and the surface, and to turbulent orographic form drag.

The turbulent interactions between the atmosphere and the surface are due to the roughness of the surface.

The turbulent orographic form drag is the stress due to the valleys, hills and mountains on horizontal scales below 5km being derived from land surface data at about 1 km resolution. See further information.

Positive (negative) values denote stress in the eastward (westward) direction.
N m**-2  
inss 230 Instantaneous northward turbulent surface stress Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is the stress on the Earth's surface at the specified time in the northward direction due to both the turbulent interactions between the atmosphere and the surface, and to turbulent orographic form drag.

The turbulent interactions between the atmosphere and the surface are due to the roughness of the surface.

The turbulent orographic form drag is the stress due to the valleys, hills and mountains on horizontal scales below 5km being derived from land surface data at about 1 km resolution. See further information.

Positive (negative) values denote stress in the northward (southward) direction.
N m**-2  
ishf 231 Instantaneous surface sensible heat flux This parameter is the transfer of heat between the Earth's surface and the atmosphere, at the specified time, through the effects of turbulent air motion (but excluding any heat transfer resulting from condensation or evaporation).

The magnitude of the sensible heat flux is governed by the difference in temperature between the surface and the overlying atmosphere, wind speed and the surface roughness. For example, cold air overlying a warm surface would produce a sensible heat flux from the land (or ocean) into the atmosphere.The ECMWF convention for vertical fluxes is positive downwards. See further documentation.
W m**-2  
ie 232 Instantaneous moisture flux This parameter is the net rate of moisture exchange between the land/ocean surface and the atmosphere, due to the processes of evaporation (including evapotranspiration) and condensation, at the specified time. By convention, downward fluxes are positive, which means that evaporation is represented by negative values and condensation by positive values. kg m**-2 s**-1  
skt 235 Skin temperature This parameter is the temperature of the surface of the Earth.

The skin temperature is the theoretical temperature that is required to satisfy the surface energy balance. It represents the temperature of the uppermost surface layer, which has no heat capacity and so can respond instantaneously to changes in surface fluxes. Skin temperature is calculated differently over land and sea.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information about the skin temperature over land and over sea.
K  
stl4 236 Soil temperature level 4 This parameter is the temperature of the soil at level 4 (in the middle of layer 4).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
tsn 238 Temperature of snow layer This parameter gives the temperature of the snow layer from the ground to the snow-air interface.

The ECMWF Integrated Forecast System (IFS) model represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box.

See further information on snow in the IFS.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
fal 243 Forecast albedo This parameter is a measure of the reflectivity of the Earth's surface. It is the fraction of solar (shortwave) radiation reflected by Earth's surface, across the solar spectrum, for both direct and diffuse radiation. Typically, snow and ice have high reflectivity with albedo values of 0.8 and above, land has intermediate values between about 0.1 and 0.4 and the ocean has low values of 0.1 or less.

Radiation from the Sun (solar, or shortwave, radiation) is partly reflected back to space by clouds and particles in the atmosphere (aerosols) and some of it is absorbed. The rest is incident on the Earth's surface, where some of it is reflected. The portion that is reflected by the Earth's surface depends on the albedo. See further documentation .

In the ECMWF Integrated Forecasting System (IFS), a climatological background albedo (observed values averaged over a period of several years) is used, modified by the model over water, ice and snow.

Albedo is often shown as a percentage (%).
(0 - 1)  
fsr 244 Forecast surface roughness This parameter is the aerodynamic roughness length in metres.

It is a measure of the surface resistance. This parameter is used to determine the air to surface transfer of momentum. For given atmospheric conditions, a higher surface roughness causes a slower near-surface wind speed.

Over the ocean, surface roughness depends on the waves. Over the land, surface roughness is derived from the vegetation type and snow cover.
m  
flsr 245 Forecast logarithm of surface roughness for heat This parameter is the natural logarithm of the roughness length for heat.

The surface roughness for heat is a measure of the surface resistance to heat transfer. This parameter is used to determine the air to surface transfer of heat. For given atmospheric conditions, a higher surface roughness for heat means that it is more difficult for the air to exchange heat with the surface. A lower surface roughness for heat that it is easier for the air to exchange heat with the surface.

Over the ocean, surface roughness for heat depends on the waves. Over sea-ice, it has a constant value of 0.001 m. Over the land, it is derived from the vegetation type and snow cover. See further information.
~  
vis 3020 Visibility A visibility parameter was introduced in the ECMWF Integrated Forecasting System (IFS) from 12 May 2015. It uses model projections of water vapour, cloud, rain and snow, and climatological aerosol fields to estimate the visibility that would be recorded by weather observers. It is calculated in the IFS at 10 m above the surface of the Earth.

Visibility is normally many kilometers, but is reduced by several meteorological factors including water droplets (fog), precipitation, humidity and aerosols.

Historically, visibility observations have been estimated by human observers judging whether they can see distant objects. More recently, visibility sensors measure the length of atmosphere over which a beam of light travels before its luminous flux is reduced to 5% of its original value.
m  
so 151130 Sea water practical salinity   psu  
ocu 151131 Eastward sea water velocity This parameter is the eastward component of the sea water velocity. It is the horizontal speed of water moving towards the east. A negative value thus indicates sea water movement towards the west.

This parameter can be combined with the northward sea water velocity to give the speed and direction of the sea water.
m s**-1  
ocv 151132 Northward sea water velocity This parameter is the northward component of the sea water velocity. It is the horizontal speed of water moving towards the north. A negative value thus indicates sea water movement towards the south.

This parameter can be combined with the eastward sea water velocity to give the speed and direction of the sea water.
m s**-1  
zos 151145 Sea surface height   m  
mld 151148 Mixed layer depth   m  
t20d 151163 Depth of 20C isotherm   m  
tav300 151164 Average potential temperature in the upper 300m   degrees C  
sav300 151175 Average salinity in the upper 300m   psu  
viwve 162071 Vertical integral of eastward water vapour flux This parameter is the horizontal rate of flow of water vapour, in the eastward direction, per metre across the flow, for a column of air extending from the surface of the Earth to the top of the atmosphere. Positive values indicate a flux from west to east. kg m**-1 s**-1  
viwvn 162072 Vertical integral of northward water vapour flux This parameter is the horizontal rate of flow of water vapour, in the northward direction, per metre across the flow, for a column of air extending from the surface of the Earth to the top of the atmosphere. Positive values indicate a flux from south to north. kg m**-1 s**-1  
sithick 174098 Sea-ice thickness   m  
cin 228001 Convective inhibition This parameter is a measure of the amount of energy required for convection to commence. If the value of this parameter is too high, then deep, moist convection is unlikely to occur even if the convective available potential energy or convective available potential energy shear are large. CIN values greater than 200 J kg-1 would be considered high.

An atmospheric layer where temperature increases with height (known as a temperature inversion) would inhibit convective uplift and is a situation in which convective inhibition would be large.
J kg**-1  
zust 228003 Friction velocity Air flowing over a surface exerts a stress that transfers momentum to the surface and slows the wind. This parameter is a theoretical wind speed at the Earth's surface that expresses the magnitude of stress. It is calculated by dividing the surface stress by air density and taking its square root. For turbulent flow, the friction velocity is approximately constant in the lowest few metres of the atmosphere.

This parameter increases with the roughness of the surface. It is used to calculate the way wind changes with height in the lowest levels of the atmosphere.
m s**-1  
dl 228007 Lake total depth This parameter is the mean depth of inland water bodies (lakes, reservoirs and rivers) and coastal waters. This field is specified from in-situ measurements and indirect estimates and is constant in time.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
m  
lmlt 228008 Lake mix-layer temperature This parameter is the temperature of the uppermost layer of inland water bodies (lakes, reservoirs and rivers) or coastal waters, that is well mixed and has a near constant temperature with depth (i.e., a uniform distribution of temperature with depth).

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below. The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

Mixing within the mixed layer can occur when the density of the surface (and near-surface) water is greater than that of the water below. Mixing can also occur through the action of wind on the surface of the lake.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
lmld 228009 Lake mix-layer depth This parameter is the thickness of the uppermost layer of inland water bodies (lakes, reservoirs and rivers) or coastal waters, that is well mixed and has a near constant temperature with depth (i.e., a uniform distribution of temperature with depth).

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below, where temperature changes with depth. The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

Mixing within the mixed layer can occur when the density of the surface (and near-surface) water is greater than that of the water below. Mixing can also occur through the action of wind on the surface of the lake.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
m  
lblt 228010 Lake bottom temperature This parameter is the temperature of water at the bottom of inland water bodies (lakes, reservoirs, rivers) and coastal waters.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
ltlt 228011 Lake total layer temperature This parameter is the mean temperature of the total water column in inland water bodies (lakes, reservoirs and rivers) and coastal waters.

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below, where temperature changes with depth. This parameter is the mean over the two layers.

The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
lshf 228012 Lake shape factor This parameter describes the way that temperature changes with depth in the thermocline layer of inland water bodies (lakes, reservoirs and rivers) and coastal waters (i.e., it describes the shape of the vertical temperature profile). It is used to calculate the lake bottom temperature and other lake-related parameters.

The ECMWF Integrated Forecasting System represents inland water bodies and coastal waters with two layers in the vertical, the mixed layer above and the thermocline below, where temperature changes with depth. The upper boundary of the thermocline is located at the mixed layer bottom, and the lower boundary of the thermocline at the lake bottom.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
dimensionless  
lict 228013 Lake ice surface temperature This parameter is the temperature of the uppermost surface of ice on inland water bodies (lakes, reservoirs, and rivers) and coastal waters. That is the temperature at the ice/atmosphere or ice/snow interface.

The ECMWF Integrated Forecasting System represents the formation and melting of ice on lakes. A single ice layer is represented.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
K  
licd 228014 Lake ice total depth This parameter is the thickness of ice on inland water bodies (lakes, reservoirs and rivers) and coastal waters.

The ECMWF Integrated Forecasting System represents the formation and melting of ice on inland water bodies. A single ice layer is represented. This parameter is the thickness of that ice layer.

ECMWF implemented a lake model in May 2015 to represent the water temperature and lake ice of all the world's major inland water bodies in the Integrated Forecasting System (IFS). The IFS differentiates between (i) ocean water, handled by the ocean model, and (ii) inland water (lakes, reservoirs and rivers) and coastal waters handled by the lake parametrisation. Lake depth and surface area (or fractional cover) are kept constant in time.
m  
fdir 228021 Total sky direct solar radiation at surface This parameter is the amount of direct solar radiation (also known as shortwave radiation) reaching the surface of the Earth. It is the amount of radiation passing through a horizontal plane, not a plane perpendicular to the direction of the Sun.

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation). See further documentation.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
cdir 228022 Clear-sky direct solar radiation at surface This parameter is the amount of direct radiation from the Sun (also known as solar or shortwave radiation) reaching the surface of the Earth, assuming clear-sky (cloudless) conditions. It is the amount of radiation passing through a horizontal plane, not a plane perpendicular to the direction of the Sun.

Solar radiation at the surface can be direct or diffuse. Solar radiation can be scattered in all directions by particles in the atmosphere, some of which reaches the surface (diffuse solar radiation). Some solar radiation reaches the surface without being scattered (direct solar radiation). See further documentation.

Clear-sky radiation quantities are computed for exactly the same atmospheric conditions of temperature, humidity, ozone, trace gases and aerosol as the corresponding total-sky quantities (clouds included), but assuming that the clouds are not there.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds.

The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
cbh 228023 Cloud base height The height above the Earth's surface of the base of the lowest cloud layer, at the specified time.

This parameter is calculated by searching from the second lowest model level upwards, to the height of the level where cloud fraction becomes greater than 1% and condensate content greater than 1.E-6 kg kg-1. Fog (i.e., cloud in the lowest model layer) is not considered when defining cloud base height.
m  
deg0l 228024 0 degrees C isothermal level (atm) The height above the Earth's surface where the temperature passes from positive to negative values, corresponding to the top of a warm layer, at the specified time. This parameter can be used to help forecast snow.

If more than one warm layer is encountered, then the zero degree level corresponds to the top of the second atmospheric layer.

This parameter is set to zero when the temperature in the whole atmosphere is below 0℃.
m  
mx2t3 228026 Maximum temperature at 2 metres in the last 3 hours The highest value of 2 metre temperature in the previous 3 hour period.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
mn2t3 228027 Minimum temperature at 2 metres in the last 3 hours The lowest value of 2 metre temperature in the previous 3 hour period.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
10fg3 228028 10 metre wind gust in the last 3 hours This parameter is the maximum wind gust in the last 3 hours at a height of ten metres above the surface of the Earth.

The WMO defines a wind gust as the maximum of the wind averaged over 3 second intervals. This duration is shorter than a model time step, and so the ECMWF Integrated Forecasting System deduces the magnitude of a gust within each time step from the time-step-averaged surface stress, surface friction, wind shear and stability. Then, the maximum wind gust is selected from the gusts at each time step during the last 3 hours.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
m s**-1  
i10fg 228029 Instantaneous 10 metre wind gust This parameter is the maximum wind gust at the specified time, at a height of ten metres above the surface of the Earth.

The WMO defines a wind gust as the maximum of the wind averaged over 3 second intervals. This duration is shorter than a model time step , and so the ECMWF Integrated Forecasting System deduces the magnitude of a gust within each time step from the time-step-averaged surface stress, surface friction, wind shear and stability.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
m s**-1  
mxcape6 228035 Maximum CAPE in the last 6 hours The maximum CAPE (convective available potential energy) value that has occurred over the last 6 hours.

CAPE is an indication of the instability (or stability) of the atmosphere and can be used to assess the potential for the development of deep convection. When air rises through a large depth of the atmosphere, extensive condensation can occur and heavy rainfall, thunderstorms and other severe weather can result.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
J kg**-1  
mxcapes6 228036 Maximum CAPES in the last 6 hours The maximum CAPES (convective available potential energy shear) value that has occurred over the last 6 hours.

High values of CAPES indicate where deep, organised convection is more likely to occur, if it is initiated. When air rises through a large depth of the atmosphere, extensive condensation can occur and heavy rainfall, thunderstorms and other severe weather can result.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
m**2 s**-2  
capes 228044 Convective available potential energy shear High values of this parameter indicate where deep, organised convection is more likely to occur, if it is initiated. When air rises through a large depth of the atmosphere, extensive condensation can occur and heavy rainfall, thunderstorms and other severe weather can result.

The likelihood of severe weather and its level of intensity tend to increase with increasing organisation of convection. Convective supercells are the most prominent example. Such organised areas of convection tend to occur where wind (intensity and/or direction) changes rapidly with height i.e., areas with strong vertical wind shear.

This parameter is the product of wind shear and the square root of convective available potential energy (CAPE). The wind shear denotes bulk shear which is a vector difference of winds at two different heights in the atmosphere (925 hPa and 500 hPa). The square root of CAPE is proportional to the maximum vertical velocity in convective updraughts.

To help determine whether deep, moist convection will be initiated or not, the probability forecast for precipitation (for example) can be used, in conjunction with this parameter.
m**2 s**-2  
hcct 228046 Height of convective cloud top The height above the Earth's surface of the top of convective cloud produced by the ECMWF Integrated Forecasting System convection scheme, at the specified time. The convection scheme represents convection at spatial scales smaller than the grid box. See further information. m  
hwbt0 228047 Height of zero-degree wet-bulb temperature The height above the Earth's surface where the wet-bulb temperature drops to 0℃, at the specified time. This parameter can be used to help forecast snow.

The wet-bulb temperature is the temperature to which the air must drop to become saturated with moisture (keeping pressure constant and accounting only for latent heat). It can also be defined as the temperature recorded by a thermometer with its bulb covered by a wet cloth or wick. The greater the difference between the dry-bulb and wet-bulb temperature, the lower the humidity.

This parameter is set to zero when the wet bulb temperature in the whole atmosphere is below 0℃.
m  
hwbt1 228048 Height of one-degree wet-bulb temperature The height above the Earth's surface where the wet-bulb temperature drops to 1℃, at the specified time. This parameter can be used to help forecast snow.

The wet-bulb temperature is the temperature to which the air must drop to become saturated with moisture (keeping pressure constant and accounting only for latent heat). It can also be defined as the temperature recorded by a thermometer with its bulb covered by a wet cloth or wick. The greater the difference between the dry-bulb and wet-bulb temperature, the lower the humidity.

This parameter is set to zero when the wet bulb temperature in the whole atmosphere is below 1℃.
m  
litoti 228050 Instantaneous total lightning flash density This parameter gives the total lightning flash rate at the specified time. Users should be aware that it is prone to large errors, e.g. due to any spatial and temporal discrepancies between model convection and observed convection.

Note that this parameter has units of flashes per square kilometre per day. Conversion of this parameter to units of flashes per 100 square kilometres per hour can give values that are easier to interpret.

This parameter accounts for cloud-to-ground flashes (between the the cloud and the Earth's surface) and intra-cloud flashes (between two cloud regions of opposite electric charge). In the ECMWF Integrated Forecasting System, the total lightning flash density is calculated using an empirical formula involving convective cloud and precipitation information, convective available potential energy (CAPE) and convective cloud base height, which are diagnosed by the convection scheme.
km**-2 day**-1  
litota3 228057 Averaged total lightning flash density in the last 3 hours This parameter gives the total lightning flash rate averaged over the last 3 hours.

Note that this parameter has units of flashes per square kilometre per day. Conversion of this parameter to units of flashes per 100 square kilometres per hour can give values that are easier to interpret.

This parameter accounts for cloud-to-ground flashes (between the cloud and the Earth's surface ) and intra-cloud flashes (between two cloud regions of opposite electric charge). In the ECMWF Integrated Forecasting System, the total lightning flash density is calculated using an empirical formula involving convective cloud and precipitation information, convective available potential energy (CAPE) and convective cloud base height, which are diagnosed by the convection scheme.
km**-2 day**-1  
litota6 228058 Averaged total lightning flash density in the last 6 hours This parameter gives the total lightning flash rate averaged over the last 6 hours.

Note that this parameter has units of flashes per square kilometre per day. Conversion of this parameter to units of flashes per 100 square kilometres per hour can give values that are easier to interpret.

This parameter accounts for cloud-to-ground flashes (between the cloud and the Earth's surface ) and intra-cloud flashes (between two cloud regions of opposite electric charge). In the ECMWF Integrated Forecasting System, the total lightning flash density is calculated using an empirical formula involving convective cloud and precipitation information, convective available potential energy (CAPE) and convective cloud base height, which are diagnosed by the convection scheme.
km**-2 day**-1  
tcslw 228088 Total column supercooled liquid water This parameter is the total amount of supercooled water in a column extending from the surface of the Earth to the top of the atmosphere. Supercooled water is water that exists in liquid form below 0oC. It is common in cold clouds and is important in the formation of precipitation. Also, supercooled water in clouds extending to the surface (i.e., fog) can cause icing/riming of various structures.

This parameter represents the area averaged value for a grid box.

Clouds contain a continuum of different sized water droplets and ice particles. The ECMWF Integrated Forecasting System (IFS) cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, conversion and aggregation are also highly simplified in the IFS.
kg m**-2  
tcrw 228089 Total column rain water This parameter is the total amount of water in droplets of raindrop size (which can fall to the surface as precipitation) in a column extending from the surface of the Earth to the top of the atmosphere.

This parameter represents the area averaged value for a grid box.

Clouds contain a continuum of different sized water droplets and ice particles. The ECMWF Integrated Forecasting System (IFS) cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, conversion and aggregation are also highly simplified in the IFS.
kg m**-2  
tcsw 228090 Total column snow water This parameter is the total amount of water in the form of snow (aggregated ice crystals which can fall to the surface as precipitation) in a column extending from the surface of the Earth to the top of the atmosphere.

This parameter represents the area averaged value for a grid box.

Clouds contain a continuum of different sized water droplets and ice particles. The ECMWF Integrated Forecasting System (IFS) cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, conversion and aggregation are also highly simplified in the IFS.
kg m**-2  
ssrdc 228129 Surface solar radiation downward clear-sky clear-sky downward shortwave radiation flux at surface computed from the model radiation scheme J m**-2  
strdc 228130 Surface thermal radiation downward clear-sky clear-sky downward longwave radiation flux at surface computed from the model radiation scheme J m**-2  
u10n 228131 Neutral wind at 10 m u-component This parameter is the eastward component of the 'neutral wind', at a height of 10 metres above the surface of the Earth.

The neutral wind is calculated from the surface stress and the corresponding roughness length by assuming that the air is neutrally stratified. The neutral wind is slower than the actual wind in stable conditions, and faster in unstable conditions. The neutral wind is, by definition, in the direction of the surface stress. The size of the roughness length depends on land surface properties or the sea state.
m s**-1  
v10n 228132 Neutral wind at 10 m v-component This parameter is the northward component of the 'neutral wind', at a height of 10 metres above the surface of the Earth.

The neutral wind is calculated from the surface stress and the corresponding roughness length by assuming that the air is neutrally stratified. The neutral wind is slower than the actual wind in stable conditions, and faster in unstable conditions. The neutral wind is, by definition, in the direction of the surface stress. The size of the roughness length depends on land surface properties or the sea state.
m s**-1  
fzra 228216 Accumulated freezing rain This parameter is the total amount of precipitation falling as freezing rain, accumulated over a particular time period which depends on the data extracted.

Freezing rain occurs when supercooled water droplets (below 0°C but still in liquid form) immediately freeze as they hit the ground (and other surfaces) to form a coating or glaze of clear ice. Freezing rain creates hazardous, extremely slippery surface conditions and can cause disruption to road, rail and air transport. If prolonged, it can damage vegetation and crops and can accumulate on power lines, causing them to collapse.

The units are depth in metres of liquid water equivalent. It is the depth the liquid water would have if it were spread evenly over the grid box. Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step
m  
ilspf 228217 Instantaneous large-scale surface precipitation fraction This parameter is the fraction of the grid box (0-1) covered by large-scale precipitation at the specified time .

Large-scale precipitation is rain and snow that falls to the Earth's surface, and is generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. Precipitation can also be due to convection generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box. See further information.
(0 - 1)  
crr 228218 Convective rain rate This parameter is the rate of rainfall (rainfall intensity), at the specified time , generated by the convection scheme in the ECMWF Integrated Forecasting System (IFS). The convection scheme represents convection at spatial scales smaller than the grid box.

Total rainfall is made up of convective and large-scale rainfall. Large-scale rainfall is generated by the cloud scheme in the IFS. The cloud scheme represents the formation and dissipation of clouds and large-scale rainfall due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid boxor larger. See further information. Rainfall is one component of precipitation. In the IFS, precipitation is rain and snow that falls to the Earth's surface.

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
lsrr 228219 Large scale rain rate This parameter is the rate of rainfall (rainfall intensity), at the specified time, generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger.

Rainfall can also be due to convection generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box. See further information. Rainfall is one component of precipitation. In the IFS, precipitation is rain and snow that falls to the Earth's surface.

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
csfr 228220 Convective snowfall rate water equivalent This parameter is the rate of snowfall (snowfall intensity), at the specified time, generated by the convection scheme in the ECMWF Integrated Forecasting System (IFS). The convection scheme represents convection at spatial scales smaller than the grid box.

Total snowfall is made up of convective and large-scale snowfall. Large-scale snowfall is generated by the cloud scheme in the IFS. The cloud scheme represents the formation and dissipation of clouds and large-scale snowfall due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. See further information. Snowfall is one component of precipitation. In the IFS, precipitation is rain and snow that falls to the Earth's surface

Snowfall rate is considered here in terms of its water equivalent. Since 1 kg of water spread over 1 square metre of surface is 1 mm thick (neglecting the effects of temperature on the density of water), the units are equivalent to mm (of liquid water) per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
lssfr 228221 Large scale snowfall rate water equivalent This parameter is the rate of snowfall (snowfall intensity), at the specified time, generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale snowfall due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger.

Snowfall can also be due to convection generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box. See further information. Snowfall is one component of precipitation. In the IFS, precipitation is rain and snow that falls to the Earth's surface

Snowfall rate is considered here in terms of its water equivalent. Since 1 kg of water spread over 1 square metre of surface is 1 mm thick (neglecting the effects of temperature on the density of water), the units are equivalent to mm (of liquid water) per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
mxtpr3 228222 Maximum total precipitation rate in the last 3 hours The maximum total precipitation rate in the previous 3 hour period. The maximum is calculated from the precipitation rate at each model time step.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. It is the sum of large-scale precipitation and convective precipitation. Large-scale precipitation is generated by the cloud scheme in the IFS. The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. Convective precipitation is generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box. See further information .

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
mntpr3 228223 Minimum total precipitation rate in the last 3 hours The minimum total precipitation rate in the previous 3 hour period. The minimum is calculated from the precipitation rate at each model time step.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. It is the sum of large-scale precipitation and convective precipitation. Large-scale precipitation is generated by the cloud scheme in the IFS. The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. Convective precipitation is generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box. See further information .

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
mxtpr6 228224 Maximum total precipitation rate in the last 6 hours The maximum total precipitation rate in the previous 6 hour period. The maximum is calculated from the precipitation rate at each model time step.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. It is the sum of large-scale precipitation and convective precipitation. Large-scale precipitation is generated by the cloud scheme in the IFS. The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. Convective precipitation is generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box. See further information.

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
mntpr6 228225 Minimum total precipitation rate in the last 6 hours The minimum total precipitation rate in the previous 6 hour period. The minimum is calculated from the precipitation rate at each model time step.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. It is the sum of large-scale precipitation and convective precipitation. Large-scale precipitation is generated by the cloud scheme in the IFS. The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. Convective precipitation is generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box. See further information.

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
kg m**-2 s**-1  
mxtpr 228226 Maximum total precipitation rate since previous post-processing The total precipitation is calculated from the combined large-scale and convective rainfall and snowfall rates every time step and the maximum is kept since the last postprocessing kg m**-2 s**-1  
200u 228239 200 metre U wind component   m s**-1  
200v 228240 200 metre V wind component   m s**-1  
200si 228241 200 metre wind speed   m s**-1  
100u 228246 100 metre U wind component This parameter is the eastward component of the 100 m wind. It is the horizontal speed of air moving towards the east, at a height of 100 metres above the surface of the Earth, in metres per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.

This parameter can be combined with the northward component to give the speed and direction of the horizontal 100 m wind.
m s**-1  
100v 228247 100 metre V wind component This parameter is the northward component of the 100 m wind. It is the horizontal speed of air moving towards the north, at a height of 100 metres above the surface of the Earth, in metres per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.

This parameter can be combined with the eastward component to give the speed and direction of the horizontal 100 m wind.
m s**-1  
pev 228251 Potential evaporation This parameter is a measure of the extent to which near-surface atmospheric conditions are conducive to the process of evaporation. It is usually considered to be the amount of evaporation, under existing atmospheric conditions, from a surface of pure water which has the temperature of the lowest layer of the atmosphere and gives an indication of the maximum possible evaporation.

Potential evaporation in the current ECMWF Integrated Forecasting System is based on surface energy balance calculations with the vegetation parameters set to 'crops/mixed farming' and assuming 'no stress from soil moisture'. In other words, evaporation is computed for agricultural land as if it is well watered and assuming that the atmosphere is not affected by this artificial surface condition. The latter may not always be realistic. Although potential evaporation is meant to provide an estimate of irrigation requirements, the method can give unrealistic results in arid conditions due to too strong evaporation forced by dry air.

This parameter is accumulated over a particular time period which depends on the data extracted.
m  
ptype 260015 Precipitation type This parameter describes the type of precipitation at the surface, at the specified time.

A precipitation type is assigned wherever there is a non-zero value of precipitation in the model output field. The precipitation type should be used together with the precipitation rate to provide, for example, an indication of potential freezing rain events.

In the ECMWF Integrated Forecasting System (IFS) there are only two predicted precipitation variables: rain and snow. Precipitation type is derived from these two predicted variables in combination with atmospheric conditions, such as temperature.

Values of precipitation type defined in the IFS:

0 = No precipitation
1 = Rain
3 = Freezing rain (i.e. supercooled raindrops which freeze on contact with the ground and other surfaces)
5 = Snow
6 = Wet snow (i.e. snow particles which are starting to melt)
7 = Mixture of rain and snow
8 = Ice pellets

These precipitation types are consistent with WMO Code Table 4.201. 2 (thunderstorm), 4 (mixed ice) and 9 (graupel), 10 (hail), 11 (drizzle) and 12 (freezing drizzle) are not diagnosed in the IFS.
code table (4.201)  
tprate 260048 Total precipitation rate This parameter is the rate of total precipitation, at the specified time.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. It is the sum of large-scale precipitation and convective precipitation. Large-scale precipitation is generated by the cloud scheme in the IFS. The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. Convective precipitation is generated by the convection scheme in the IFS. The convection scheme represents convection at spatial scales smaller than the grid box.See further information. Precipitation parameters do not include fog, dew or the precipitation that evaporates in the atmosphere before it lands at the surface of the Earth.

1 kg of water spread over 1 square metre of surface is 1 mm deep (neglecting the effects of temperature on the density of water), therefore the units are equivalent to mm per second.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step .
kg m**-2 s**-1  
ceil 260109 Ceiling The height above the Earth's surface of the base of the lowest layer of cloud with a covering of more than 50% of the model grid box. Cloud ceiling is a measurement used in the aviation industry to indicate airport landing conditions.

This parameter is calculated by searching from the second lowest model level upwards, to the height of the level where cloud fraction becomes greater than 50% and condensate content greater than 1.E-6 kg kg-1. Fog (i.e., cloud in the lowest model layer) is not considered when defining ceiling.
m  
kx 260121 K index This parameter is a measure of potential for a thunderstorm to develop calculated from the temperature and dew point temperature in the lower part of the atmosphere. The calculation uses the temperature at 850, 700 and 500 hPa and dewpoint temperature at 850 and 700 hPa. Higher values of K indicate a higher potential for the development of thunderstorms.

This parameter is related to the probability of occurrence of a thunderstorm:
Parameter value Thunderstorm Probability
<20 K No thunderstorm.
20-25 K Isolated thunderstorms.
26-30 K Widely scattered thunderstorms.
31-35 K Scattered thunderstorms.
>35 K Numerous thunderstorms
K  
totalx 260123 Total totals index This parameter gives an indication of the probability of occurrence of a thunderstorm and its severity by using the vertical gradient of temperature and humidity.
 
TT index Thunderstorm Probability
<44 Thunderstorms not likely.
44-50 Thunderstorms likely.
51-52 Isolated severe thunderstorms.
53-56 Widely scattered severe thunderstorms.
56-60 Scattered severe thunderstorms more likely.

The total totals index is the temperature difference between 850 hPa (near surface) and 500 hPa (mid-troposphere) (lapse rate) plus a measure of the moisture content between 850 hPa and 500 hPa. The probability of deep convection tends to increase with increasing lapse rate and atmospheric moisture content.

There are a number of limitations to this index. Also, the interpretation of the index value varies with season and location. See further information.

K  

I-i: Atmospheric fields -Pressure levels - analysis

Pressure level - analysis

All parameters are available at levels
1000, 950, 925, 900, 850, 800, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2, 1 hPa

Analysis fields can be provided for base time 00, 06, 12 or 18

 

Short Name ID Long Name Description Units Additional information
pv 60 Potential vorticity Potential vorticity is a measure of the capacity for air to rotate in the atmosphere. If we ignore the effects of heating and friction, potential vorticity is conserved following an air parcel. It is used to look for places where large wind storms are likely to originate and develop. Potential vorticity increases strongly above the tropopause and therefore, it can also be used in studies related to the stratosphere and stratosphere-troposphere exchanges.

Large wind storms develop when a column of air in the atmosphere starts to rotate. Potential vorticity is calculated from the wind, temperature and pressure across a column of air in the atmosphere.
K m**2 kg**-1 s**-1  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
t 130 Temperature This parameter is the temperature in the atmosphere.

It has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

This parameter is available on multiple levels through the atmosphere.
K  
u 131 U component of wind This parameter is the eastward component of the wind. It is the horizontal speed of air moving towards the east, in metres per second. A negative sign thus indicates air movement towards the west.

This parameter can be combined with the V component of wind to give the speed and direction of the horizontal wind.
m s**-1  
v 132 V component of wind This parameter is the northward component of the wind. It is the horizontal speed of air moving towards the north, in metres per second. A negative sign thus indicates air movement towards the south.

This parameter can be combined with the U component of wind to give the speed and direction of the horizontal wind.
m s**-1  
q 133 Specific humidity This parameter is the mass of water vapour per kilogram of moist air.

The total mass of moist air is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow.
kg kg**-1  
w 135 Vertical velocity This parameter is the speed of air motion in the upward or downward direction. The ECMWF Integrated Forecasting System (IFS) uses a pressure based vertical co-ordinate system and pressure decreases with height, therefore negative values of vertical velocity indicate upward motion.

Vertical velocity can be useful to understand the large-scale dynamics of the atmosphere, including areas of upward motion/ascent (negative values) and downward motion/subsidence (positive values).
Pa s**-1  
vo 138 Vorticity (relative) This parameter is a measure of the rotation of air in the horizontal, around a vertical axis, relative to a fixed point on the surface of the Earth.

On the scale of weather systems, troughs (weather features that can include rain) are associated with anticlockwise rotation (in the northern hemisphere), and ridges (weather features that bring light or still winds) are associated with clockwise rotation.

Adding the rotation of the Earth, the so-called Coriolis parameter, to the relative vorticity produces the absolute vorticity.
s**-1  
d 155 Divergence This parameter is the horizontal divergence of velocity. It is the rate at which air is spreading out horizontally from a point, per square metre. This parameter is positive for air that is spreading out, or diverging, and negative for the opposite, for air that is concentrating, or converging (convergence). s**-1  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
r 157 Relative humidity This parameter is the water vapour pressure as a percentage of the value at which the air becomes saturated (the point at which water vapour begins to condense into liquid water or deposition into ice).

For temperatures over 0°C (273.15 K) it is calculated for saturation over water. At temperatures below -23°C it is calculated for saturation over ice. Between -23°C and 0°C this parameter is calculated by interpolating between the ice and water values using a quadratic function.

See more information about the model's relative humidity calculation.
%  
o3 203 Ozone mass mixing ratio This parameter is the mass of ozone per kilogram of air.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation.

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

Most of the IFS chemical species are archived as mass mixing ratios [kg kg-1]. This link explains how to convert to concentration in terms of mass per unit volume.
kg kg**-1  

Pressure levels- forecast

Pressure level - forecast

All parameters are available at levels
1000, 950, 925, 900, 850, 800, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2, 1 hPa

  Forecast time step Base time
T+0 to T+90   Hourly   00 UTC, 06 UTC, 12 UTC and 18 UTC
 T+93 to T+144 3-hourly 00 UTC and 12 UTC
T+150h to T+240h 6-hourly 00 UTC and 12 UTC
Short Name ID Long Name Description Units Additional information
pv 60 Potential vorticity Potential vorticity is a measure of the capacity for air to rotate in the atmosphere. If we ignore the effects of heating and friction, potential vorticity is conserved following an air parcel. It is used to look for places where large wind storms are likely to originate and develop. Potential vorticity increases strongly above the tropopause and therefore, it can also be used in studies related to the stratosphere and stratosphere-troposphere exchanges.

Large wind storms develop when a column of air in the atmosphere starts to rotate. Potential vorticity is calculated from the wind, temperature and pressure across a column of air in the atmosphere.
K m**2 kg**-1 s**-1  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
t 130 Temperature This parameter is the temperature in the atmosphere.

It has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

This parameter is available on multiple levels through the atmosphere.
K  
u 131 U component of wind This parameter is the eastward component of the wind. It is the horizontal speed of air moving towards the east, in metres per second. A negative sign thus indicates air movement towards the west.

This parameter can be combined with the V component of wind to give the speed and direction of the horizontal wind.
m s**-1  
v 132 V component of wind This parameter is the northward component of the wind. It is the horizontal speed of air moving towards the north, in metres per second. A negative sign thus indicates air movement towards the south.

This parameter can be combined with the U component of wind to give the speed and direction of the horizontal wind.
m s**-1  
q 133 Specific humidity This parameter is the mass of water vapour per kilogram of moist air.

The total mass of moist air is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow.
kg kg**-1  
w 135 Vertical velocity This parameter is the speed of air motion in the upward or downward direction. The ECMWF Integrated Forecasting System (IFS) uses a pressure based vertical co-ordinate system and pressure decreases with height, therefore negative values of vertical velocity indicate upward motion.

Vertical velocity can be useful to understand the large-scale dynamics of the atmosphere, including areas of upward motion/ascent (negative values) and downward motion/subsidence (positive values).
Pa s**-1  
vo 138 Vorticity (relative) This parameter is a measure of the rotation of air in the horizontal, around a vertical axis, relative to a fixed point on the surface of the Earth.

On the scale of weather systems, troughs (weather features that can include rain) are associated with anticlockwise rotation (in the northern hemisphere), and ridges (weather features that bring light or still winds) are associated with clockwise rotation.

Adding the rotation of the Earth, the so-called Coriolis parameter, to the relative vorticity produces the absolute vorticity.
s**-1  
lnsp 152 Logarithm of surface pressure This parameter is the natural logarithm of pressure (force per unit area) of the atmosphere on the surface of land, sea and inland water. Numerical weather prediction models often utilise the logarithm of surface pressure in their calculations. ~  
d 155 Divergence This parameter is the horizontal divergence of velocity. It is the rate at which air is spreading out horizontally from a point, per square metre. This parameter is positive for air that is spreading out, or diverging, and negative for the opposite, for air that is concentrating, or converging (convergence). s**-1  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
r 157 Relative humidity This parameter is the water vapour pressure as a percentage of the value at which the air becomes saturated (the point at which water vapour begins to condense into liquid water or deposition into ice).

For temperatures over 0°C (273.15 K) it is calculated for saturation over water. At temperatures below -23°C it is calculated for saturation over ice. Between -23°C and 0°C this parameter is calculated by interpolating between the ice and water values using a quadratic function.

See more information about the model's relative humidity calculation.
%  
o3 203 Ozone mass mixing ratio This parameter is the mass of ozone per kilogram of air.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation.

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

Most of the IFS chemical species are archived as mass mixing ratios [kg kg-1]. This link explains how to convert to concentration in terms of mass per unit volume.
kg kg**-1  
clwc 246 Specific cloud liquid water content This parameter is the mass of cloud liquid water droplets per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Water within clouds can be liquid or ice, or a combination of the two. See further information about the cloud formulation.
kg kg**-1  
ciwc 247 Specific cloud ice water content This parameter is the mass of cloud ice particles per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Water within clouds can be liquid or ice, or a combination of the two.
Note that 'cloud frozen water' is the same as 'cloud ice water'.

See further information about the cloud formulation.
kg kg**-1  
cc 248 Fraction of cloud cover This parameter is the proportion of a grid box covered by cloud (liquid or ice). This parameter is available on multiple levels through the atmosphere. (0 - 1)  

Model Level - analysis

Model levels range: 1 to 137

Analysis fields can be provided for base time 00, 06, 12 or 18

Model level parameters are produced in GRIB2 format.

Short Name ID Long Name Description Units Additional information
crwc 75 Specific rain water content The mass of water produced from large-scale clouds that is of raindrop size and so can fall to the surface as precipitation.

Large-scale clouds are generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. See further information.

The quantity is expressed in kilograms per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Clouds contain a continuum of different sized water droplets and ice particles. The IFS cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, phase transition and aggregation are also highly simplified in the IFS.
kg kg**-1  
cswc 76 Specific snow water content The mass of snow (aggregated ice crystals) produced from large-scale clouds that can fall to the surface as precipitation.

Large-scale clouds are generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. See further information.

The mass is expressed in kilograms per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Clouds contain a continuum of different sized water droplets and ice particles. The IFS cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, phase transition and aggregation are also highly simplified in the IFS.
kg kg**-1  
etadot 77 Eta-coordinate vertical velocity This parameter is the rate of air motion in the upward or downward direction. The ECMWF Integrated Forecasting System (IFS) uses a pressure and terrain-based vertical coordinate system called eta-coordinate. Since pressure in the atmosphere decreases with height, negative values of eta-coordinate vertical velocity indicate upward motion.

This parameter is used in the IFS to calculate the vertical transport, or advection, of atmospheric quantities such as moisture.
s**-1  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
t 130 Temperature This parameter is the temperature in the atmosphere.

It has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

This parameter is available on multiple levels through the atmosphere.
K  
u 131 U component of wind This parameter is the eastward component of the wind. It is the horizontal speed of air moving towards the east, in metres per second. A negative sign thus indicates air movement towards the west.

This parameter can be combined with the V component of wind to give the speed and direction of the horizontal wind.
m s**-1  
v 132 V component of wind This parameter is the northward component of the wind. It is the horizontal speed of air moving towards the north, in metres per second. A negative sign thus indicates air movement towards the south.

This parameter can be combined with the U component of wind to give the speed and direction of the horizontal wind.
m s**-1  
q 133 Specific humidity This parameter is the mass of water vapour per kilogram of moist air.

The total mass of moist air is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow.
kg kg**-1  
w 135 Vertical velocity This parameter is the speed of air motion in the upward or downward direction. The ECMWF Integrated Forecasting System (IFS) uses a pressure based vertical co-ordinate system and pressure decreases with height, therefore negative values of vertical velocity indicate upward motion.

Vertical velocity can be useful to understand the large-scale dynamics of the atmosphere, including areas of upward motion/ascent (negative values) and downward motion/subsidence (positive values).
Pa s**-1  
vo 138 Vorticity (relative) This parameter is a measure of the rotation of air in the horizontal, around a vertical axis, relative to a fixed point on the surface of the Earth.

On the scale of weather systems, troughs (weather features that can include rain) are associated with anticlockwise rotation (in the northern hemisphere), and ridges (weather features that bring light or still winds) are associated with clockwise rotation.

Adding the rotation of the Earth, the so-called Coriolis parameter, to the relative vorticity produces the absolute vorticity.
s**-1  
lnsp 152 Logarithm of surface pressure This parameter is the natural logarithm of pressure (force per unit area) of the atmosphere on the surface of land, sea and inland water. Numerical weather prediction models often utilise the logarithm of surface pressure in their calculations. ~  
d 155 Divergence This parameter is the horizontal divergence of velocity. It is the rate at which air is spreading out horizontally from a point, per square metre. This parameter is positive for air that is spreading out, or diverging, and negative for the opposite, for air that is concentrating, or converging (convergence). s**-1  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
o3 203 Ozone mass mixing ratio This parameter is the mass of ozone per kilogram of air.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation.

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

Most of the IFS chemical species are archived as mass mixing ratios [kg kg-1]. This link explains how to convert to concentration in terms of mass per unit volume.
kg kg**-1  
clwc 246 Specific cloud liquid water content This parameter is the mass of cloud liquid water droplets per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Water within clouds can be liquid or ice, or a combination of the two. See further information about the cloud formulation.
kg kg**-1  
ciwc 247 Specific cloud ice water content This parameter is the mass of cloud ice particles per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Water within clouds can be liquid or ice, or a combination of the two.
Note that 'cloud frozen water' is the same as 'cloud ice water'.

See further information about the cloud formulation.
kg kg**-1  
cc 248 Fraction of cloud cover This parameter is the proportion of a grid box covered by cloud (liquid or ice). This parameter is available on multiple levels through the atmosphere. (0 - 1)  

Model Level - forecast

Model Level - forecast

Model level parameters are produced in GRIB2 format.

  Forecast time step Base time
T+0 to T+90   Hourly   00 UTC, 06 UTC, 12 UTC and 18 UTC
 T+93 to T+144 3-hourly 00 UTC and 12 UTC
T+150h to T+240h 6-hourly 00 UTC and 12 UTC
Short Name ID Long Name Description Units Additional information
crwc 75 Specific rain water content The mass of water produced from large-scale clouds that is of raindrop size and so can fall to the surface as precipitation.

Large-scale clouds are generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. See further information.

The quantity is expressed in kilograms per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Clouds contain a continuum of different sized water droplets and ice particles. The IFS cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, phase transition and aggregation are also highly simplified in the IFS.
kg kg**-1  
cswc 76 Specific snow water content The mass of snow (aggregated ice crystals) produced from large-scale clouds that can fall to the surface as precipitation.

Large-scale clouds are generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of a grid box or larger. See further information.

The mass is expressed in kilograms per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Clouds contain a continuum of different sized water droplets and ice particles. The IFS cloud scheme simplifies this to represent a number of discrete cloud droplets/particles including: cloud water droplets, raindrops, ice crystals and snow (aggregated ice crystals). The processes of droplet formation, phase transition and aggregation are also highly simplified in the IFS.
kg kg**-1  
etadot 77 Eta-coordinate vertical velocity This parameter is the rate of air motion in the upward or downward direction. The ECMWF Integrated Forecasting System (IFS) uses a pressure and terrain-based vertical coordinate system called eta-coordinate. Since pressure in the atmosphere decreases with height, negative values of eta-coordinate vertical velocity indicate upward motion.

This parameter is used in the IFS to calculate the vertical transport, or advection, of atmospheric quantities such as moisture.
s**-1  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
t 130 Temperature This parameter is the temperature in the atmosphere.

It has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

This parameter is available on multiple levels through the atmosphere.
K  
u 131 U component of wind This parameter is the eastward component of the wind. It is the horizontal speed of air moving towards the east, in metres per second. A negative sign thus indicates air movement towards the west.

This parameter can be combined with the V component of wind to give the speed and direction of the horizontal wind.
m s**-1  
v 132 V component of wind This parameter is the northward component of the wind. It is the horizontal speed of air moving towards the north, in metres per second. A negative sign thus indicates air movement towards the south.

This parameter can be combined with the U component of wind to give the speed and direction of the horizontal wind.
m s**-1  
q 133 Specific humidity This parameter is the mass of water vapour per kilogram of moist air.

The total mass of moist air is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow.
kg kg**-1  
w 135 Vertical velocity This parameter is the speed of air motion in the upward or downward direction. The ECMWF Integrated Forecasting System (IFS) uses a pressure based vertical co-ordinate system and pressure decreases with height, therefore negative values of vertical velocity indicate upward motion.

Vertical velocity can be useful to understand the large-scale dynamics of the atmosphere, including areas of upward motion/ascent (negative values) and downward motion/subsidence (positive values).
Pa s**-1  
vo 138 Vorticity (relative) This parameter is a measure of the rotation of air in the horizontal, around a vertical axis, relative to a fixed point on the surface of the Earth.

On the scale of weather systems, troughs (weather features that can include rain) are associated with anticlockwise rotation (in the northern hemisphere), and ridges (weather features that bring light or still winds) are associated with clockwise rotation.

Adding the rotation of the Earth, the so-called Coriolis parameter, to the relative vorticity produces the absolute vorticity.
s**-1  
lnsp 152 Logarithm of surface pressure This parameter is the natural logarithm of pressure (force per unit area) of the atmosphere on the surface of land, sea and inland water. Numerical weather prediction models often utilise the logarithm of surface pressure in their calculations. ~  
d 155 Divergence This parameter is the horizontal divergence of velocity. It is the rate at which air is spreading out horizontally from a point, per square metre. This parameter is positive for air that is spreading out, or diverging, and negative for the opposite, for air that is concentrating, or converging (convergence). s**-1  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
o3 203 Ozone mass mixing ratio This parameter is the mass of ozone per kilogram of air.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation.

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

Most of the IFS chemical species are archived as mass mixing ratios [kg kg-1]. This link explains how to convert to concentration in terms of mass per unit volume.
kg kg**-1  
clwc 246 Specific cloud liquid water content This parameter is the mass of cloud liquid water droplets per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Water within clouds can be liquid or ice, or a combination of the two. See further information about the cloud formulation.
kg kg**-1  
ciwc 247 Specific cloud ice water content This parameter is the mass of cloud ice particles per kilogram of the total mass of moist air. The 'total mass of moist air' is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Water within clouds can be liquid or ice, or a combination of the two.
Note that 'cloud frozen water' is the same as 'cloud ice water'.

See further information about the cloud formulation.
kg kg**-1  
cc 248 Fraction of cloud cover This parameter is the proportion of a grid box covered by cloud (liquid or ice). This parameter is available on multiple levels through the atmosphere. (0 - 1)  

Potential vorticity levels (Analysis)

Short Name ID Long Name Description Units Additional information
pt 3 Potential temperature   K  
pres 54 Pressure   Pa  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
u 131 U component of wind This parameter is the eastward component of the wind. It is the horizontal speed of air moving towards the east, in metres per second. A negative sign thus indicates air movement towards the west.

This parameter can be combined with the V component of wind to give the speed and direction of the horizontal wind.
m s**-1  
v 132 V component of wind This parameter is the northward component of the wind. It is the horizontal speed of air moving towards the north, in metres per second. A negative sign thus indicates air movement towards the south.

This parameter can be combined with the U component of wind to give the speed and direction of the horizontal wind.
m s**-1  
q 133 Specific humidity This parameter is the mass of water vapour per kilogram of moist air.

The total mass of moist air is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow.
kg kg**-1  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
o3 203 Ozone mass mixing ratio This parameter is the mass of ozone per kilogram of air.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation.

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

Most of the IFS chemical species are archived as mass mixing ratios [kg kg-1]. This link explains how to convert to concentration in terms of mass per unit volume.
kg kg**-1  

Potential vorticity levels (Forecast)

Short Name ID Long Name Description Units Additional information
pt 3 Potential temperature   K  
pres 54 Pressure   Pa  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
u 131 U component of wind This parameter is the eastward component of the wind. It is the horizontal speed of air moving towards the east, in metres per second. A negative sign thus indicates air movement towards the west.

This parameter can be combined with the V component of wind to give the speed and direction of the horizontal wind.
m s**-1  
v 132 V component of wind This parameter is the northward component of the wind. It is the horizontal speed of air moving towards the north, in metres per second. A negative sign thus indicates air movement towards the south.

This parameter can be combined with the U component of wind to give the speed and direction of the horizontal wind.
m s**-1  
q 133 Specific humidity This parameter is the mass of water vapour per kilogram of moist air.

The total mass of moist air is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow.
kg kg**-1  
gh 156 Geopotential Height This parameter is a measure of the height of a point in the atmosphere in relation to its potential energy. It is calculated by dividing the geopotential by the Earth's mean gravitational acceleration, g (=9.80665 m s-2). The geopotential is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. Geopotential is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

This parameter plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges. At the surface of the Earth, this parameter shows the variations in geopotential height of the surface, and is often referred to as the orography.

The units of this parameter are geopotential metres. A geopotential metre is approximately 2% shorter than a geometric metre.
gpm  
o3 203 Ozone mass mixing ratio This parameter is the mass of ozone per kilogram of air.

In the ECMWF Integrated Forecasting System (IFS), there is a simplified representation of ozone chemistry (including representation of the chemistry which has caused the ozone hole). Ozone is also transported around in the atmosphere through the motion of air. See further documentation.

Naturally occurring ozone in the stratosphere helps protect organisms at the surface of the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. Ozone near the surface, often produced because of pollution, is harmful to organisms.

Most of the IFS chemical species are archived as mass mixing ratios [kg kg-1]. This link explains how to convert to concentration in terms of mass per unit volume.
kg kg**-1  

I-ii: Time series of weather parameters (post-processed output)

The products consist of values of the individual members of the real-time forecast at grid points (single locations). The products are provided in BUFR code.

  Forecast time step Base time
 T+0 to T+240h 6-hourly 00 UTC and 12 UTC
Short Name ID Long Name Description Units Additional information
swvl1 39 Volumetric soil water layer 1 This parameter is the volume of water in soil layer 1 (0 - 7cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl2 40 Volumetric soil water layer 2 This parameter is the volume of water in soil layer 2 (7 - 28cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl3 41 Volumetric soil water layer 3 This parameter is the volume of water in soil layer 3 (28 - 100cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
swvl4 42 Volumetric soil water layer 4 This parameter is the volume of water in soil layer 4 (100 - 289cm, the surface is at 0cm).

The ECMWF Integrated Forecasting System model has a four-layer representation of soil:
Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

The volumetric soil water is associated with the soil texture (or classification), soil depth, and the underlying groundwater level.
m**3 m**-3  
mx2t6 121 Maximum temperature at 2 metres in the last 6 hours The highest value of 2 metre temperature in the previous 6 hour period.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
mn2t6 122 Minimum temperature at 2 metres in the last 6 hours The lowest value of 2 metre temperature in the previous 6 hour period.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
10fg6 123 10 metre wind gust in the last 6 hours This parameter is the maximum wind gust in the last 6 hours at a height of ten metres above the surface of the Earth.

The WMO defines a wind gust as the maximum of the wind averaged over 3 second intervals. This duration is shorter than a model time step, and so the ECMWF Integrated Forecasting System deduces the magnitude of a gust within each time step from the time-step-averaged surface stress, surface friction, wind shear and stability. Then, the maximum wind gust is selected from the gusts at each time step during the last 6 hours.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box and model time step.
m s**-1  
z 129 Geopotential This parameter is the gravitational potential energy of a unit mass, at a particular location, relative to mean sea level. It is also the amount of work that would have to be done, against the force of gravity, to lift a unit mass to that location from mean sea level.

The geopotential height can be calculated by dividing the geopotential by the Earth's gravitational acceleration, g (=9.80665 m s-2). The geopotential height plays an important role in synoptic meteorology (analysis of weather patterns). Charts of geopotential height plotted at constant pressure levels (e.g., 300, 500 or 850 hPa) can be used to identify weather systems such as cyclones, anticyclones, troughs and ridges.

At the surface of the Earth, this parameter shows the variations in geopotential (height) of the surface, and is often referred to as the orography.
m**2 s**-2  
sp 134 Surface pressure This parameter is the pressure (force per unit area) of the atmosphere on the surface of land, sea and in-land water.

It is a measure of the weight of all the air in a column vertically above the area of the Earth's surface represented at a fixed point.

Surface pressure is often used in combination with temperature to calculate air density.

The strong variation of pressure with altitude makes it difficult to see the low and high pressure systems over mountainous areas, so mean sea level pressure, rather than surface pressure, is normally used for this purpose.

The units of this parameter are Pascals (Pa). Surface pressure is often measured in hPa and sometimes is presented in the old units of millibars, mb (1 hPa = 1 mb= 100 Pa).
Pa  
stl1 139 Soil temperature level 1 This parameter is the temperature of the soil at level 1 (in the middle of layer 1).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
sd 141 Snow depth This parameter is the depth of snow from the snow-covered area of a grid box.

Its units are metres of water equivalent, so it is the depth the water would have if the snow melted and was spread evenly over the whole grid box. The ECMWF Integrated Forecast System represents snow as a single additional layer over the uppermost soil level. The snow may cover all or part of the grid box.

See further information.
m of water equivalent  
lsp 142 Large-scale precipitation This parameter is the accumulated liquid and frozen water, comprising rain and snow, that falls to the Earth's surface and which is generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of the grid box or larger. Precipitation can also be generated by the convection scheme in the IFS, which represents convection at spatial scales smaller than the grid box. See further information. This parameter does not include fog, dew or the precipitation that evaporates in the atmosphere before it lands at the surface of the Earth.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m  
cp 143 Convective precipitation This parameter is the accumulated liquid and frozen water, comprising rain and snow, that falls to the Earth's surface and which is generated by the convection scheme in the ECMWF Integrated Forecasting System (IFS). The convection scheme represents convection at spatial scales smaller than the grid box. Precipitation can also be generated by the cloud scheme in the IFS, which represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly at spatial scales of the grid box or larger. See further information. This parameter does not include fog, dew or the precipitation that evaporates in the atmosphere before it lands at the surface of the Earth.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m  
sf 144 Snowfall This parameter is the accumulated snow that falls to the Earth's surface. It is the sum of large-scale snowfall and convective snowfall. Large-scale snowfall is generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of the grid box or larger. Convective snowfall is generated by the convection scheme in the IFS, which represents convection at spatial scales smaller than the grid box. See further information.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m of water equivalent  
msl 151 Mean sea level pressure This parameter is the pressure (force per unit area) of the atmosphere adjusted to the height of mean sea level.

It is a measure of the weight that all the air in a column vertically above the area of Earth's surface would have at that point, if the point were located at the mean sea level. It is calculated over all surfaces - land, sea and in-land water.

Maps of mean sea level pressure are used to identify the locations of low and high pressure systems, often referred to as cyclones and anticyclones. Contours of mean sea level pressure also indicate the strength of the wind. Tightly packed contours show stronger winds.

The units of this parameter are pascals (Pa). Mean sea level pressure is often measured in hPa and sometimes is presented in the old units of millibars, mb (1 hPa = 1 mb = 100 Pa).
Pa  
tcc 164 Total cloud cover This parameter is the proportion of a grid box covered by cloud. Total cloud cover is a single level field calculated from the cloud occurring at different model levels through the atmosphere. Assumptions are made about the degree of overlap/randomness between clouds at different heights.

Cloud fractions vary from 0 to 1.
(0 - 1)  
10u 165 10 metre U wind component This parameter is the eastward component of the 10m wind. It is the horizontal speed of air moving towards the east, at a height of ten metres above the surface of the Earth, in metres per second.

Care should be taken when comparing this parameter with observations, because wind observations vary on small space and time scales and are affected by the local terrain, vegetation and buildings that are represented only on average in the ECMWF Integrated Forecasting System.

This parameter can be combined with the V component of 10m wind to give the speed and direction of the horizontal 10m wind.
m s**-1  
10v 166 10 metre V wind component This parameter is the northward component of the 10m wind. It is the horizontal speed of air moving towards the north, at a height of ten metres above the surface of the Earth, in metres per second.

Care should be taken when comparing this parameter with observations, because wind observations vary on small space and time scales and are affected by the local terrain, vegetation and buildings that are represented only on average in the ECMWF Integrated Forecasting System.

This parameter can be combined with the U component of 10m wind to give the speed and direction of the horizontal 10m wind.
m s**-1  
2t 167 2 metre temperature This parameter is the temperature of air at 2m above the surface of land, sea or in-land waters.

2m temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information .

This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
2d 168 2 metre dewpoint temperature This parameter is the temperature to which the air, at 2 metres above the surface of the Earth, would have to be cooled for saturation to occur.

It is a measure of the humidity of the air. Combined with temperature and pressure, it can be used to calculate the relative humidity.

2m dew point temperature is calculated by interpolating between the lowest model level and the Earth's surface, taking account of the atmospheric conditions. See further information.This parameter has units of kelvin (K). Temperature measured in kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.
K  
ssrd 169 Surface solar radiation downwards This parameter is the amount of solar radiation (also known as shortwave radiation) that reaches a horizontal plane at the surface of the Earth. This parameter comprises both direct and diffuse solar radiation.

Radiation from the Sun (solar, or shortwave, radiation) is partly reflected back to space by clouds and particles in the atmosphere (aerosols) and some of it is absorbed. The rest is incident on the Earth's surface (represented by this parameter). See further documentation.

To a reasonably good approximation, this parameter is the model equivalent of what would be measured by a pyranometer (an instrument used for measuring solar radiation) at the surface. However, care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.

This parameter is accumulated over a particular time period which depends on the data extracted. The units are joules per square metre (J m-2). To convert to watts per square metre (W m-2), the accumulated values should be divided by the accumulation period expressed in seconds. The ECMWF convention for vertical fluxes is positive downwards.
J m**-2  
stl2 170 Soil temperature level 2 This parameter is the temperature of the soil at level 2 (in the middle of layer 2).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
lsm 172 Land-sea mask This parameter is the proportion of land, as opposed to ocean or inland waters (lakes, reservoirs, rivers and coastal waters), in a grid box.
This parameter has values ranging between zero and one and is dimensionless.
In cycles of the ECMWF Integrated Forecasting System (IFS) from CY41R1 (introduced in May 2015) onwards, grid boxes where this parameter has a value above 0.5 can be comprised of a mixture of land and inland water but not ocean. Grid boxes with a value of 0.5 and below can only be comprised of a water surface. In the latter case, the lake cover is used to determine how much of the water surface is ocean or inland water.
In cycles of the IFS before CY41R1, grid boxes where this parameter has a value above 0.5 can only be comprised of land and those grid boxes with a value of 0.5 and below can only be comprised of ocean. In these older model cycles, there is no differentiation between ocean and inland water.
(0 - 1)  
stl3 183 Soil temperature level 3 This parameter is the temperature of the soil at level 3 (in the middle of layer 3).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  
lcc 186 Low cloud cover This parameter is the proportion of a grid box covered by cloud occurring in the lower levels of the troposphere. Low cloud is a single level field calculated from cloud occurring on model levels with a pressure greater than 0.8 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), low cloud would be calculated using levels with a pressure greater than 800 hPa (below approximately 2km (assuming a 'standard atmosphere')).

The low cloud cover parameter is calculated from cloud cover for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
mcc 187 Medium cloud cover This parameter is the proportion of a grid box covered by cloud occurring in the middle levels of the troposphere. Medium cloud is a single level field calculated from cloud occurring on model levels with a pressure between 0.45 and 0.8 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), medium cloud would be calculated using levels with a pressure of less than or equal to 800 hPa and greater than or equal to 450 hPa (between approximately 2km and 6km (assuming a 'standard atmosphere')).

The medium cloud parameter is calculated from cloud cover for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
hcc 188 High cloud cover The proportion of a grid box covered by cloud occurring in the high levels of the troposphere. High cloud is a single level field calculated from cloud occurring on model levels with a pressure less than 0.45 times the surface pressure. So, if the surface pressure is 1000 hPa (hectopascal), high cloud would be calculated using levels with a pressure of less than 450 hPa (approximately 6km and above ( assuming a `standard atmosphere`)).

The high cloud cover parameter is calculated from cloud for the appropriate model levels as described above. Assumptions are made about the degree of overlap/randomness between clouds in different model levels.

Cloud fractions vary from 0 to 1.
(0 - 1)  
tp 228 Total precipitation This parameter is the accumulated liquid and frozen water, comprising rain and snow, that falls to the Earth's surface. It is the sum of large-scale precipitation and convective precipitation. Large-scale precipitation is generated by the cloud scheme in the ECMWF Integrated Forecasting System (IFS). The cloud scheme represents the formation and dissipation of clouds and large-scale precipitation due to changes in atmospheric quantities (such as pressure, temperature and moisture) predicted directly by the IFS at spatial scales of the grid box or larger. Convective precipitation is generated by the convection scheme in the IFS, which represents convection at spatial scales smaller than the grid box. See further information. This parameter does not include fog, dew or the precipitation that evaporates in the atmosphere before it lands at the surface of the Earth.

This parameter is the total amount of water accumulated over a particular time period which depends on the data extracted. The units of this parameter are depth in metres of water equivalent. It is the depth the water would have if it were spread evenly over the grid box.

Care should be taken when comparing model parameters with observations, because observations are often local to a particular point in space and time, rather than representing averages over a model grid box.
m  
stl4 236 Soil temperature level 4 This parameter is the temperature of the soil at level 4 (in the middle of layer 4).

The ECMWF Integrated Forecasting System (IFS) has a four-layer representation of soil, where the surface is at 0cm:

Layer 1: 0 - 7cm
Layer 2: 7 - 28cm
Layer 3: 28 - 100cm
Layer 4: 100 - 289cm

Soil temperature is set at the middle of each layer, and heat transfer is calculated at the interfaces between them. It is assumed that there is no heat transfer out of the bottom of the lowest layer.

This parameter has units of Kelvin (K). Temperature measured in Kelvin can be converted to degrees Celsius (°C) by subtracting 273.15.

See further information.
K  

I-iii Tropical cyclones tracks (post-processed output)

Tropical cyclones tracks products are provided in BUFR code free of information charge.

Tropical cyclone tracks will only produce data when a cyclone is forecast.

  Forecast time step Base time
 T+0 to T+240   00 UTC and 12 UTC
Short name Long name Level type Type Base time Steps
TC Tropical cyclone SFC TF 00/12 240

I-iv Simulated satellite data (post-processed output)

This data is produced using relevant atmospheric model profiles and surface parameters from the operational high-resolution forecast. These are used to calculate brightness temperatures, which can be visualised as simulated satellite images.

  Forecast time step Base time
 T+0 to T+144 3-hourly 00 UTC and 12 UTC
T+150h to T+240h 6-hourly 00 UTC and 12 UTC
Short Name ID Long Name Description Units Additional information
clbt 260510 Cloudy brightness temperature Cloudy brightness temperature K