Set III - Atmospheric model Ensemble 15-day forecast (ENS)

Configure and order Set III

Ensemble (ENS) of forecasts providing an estimate of the reliability of a single forecast.

ENS offers  "High Frequency products"  until step 144:

  • 4 daily runs: 00, 06, 12 and 18 UTC
  • hourly until step 90
  • 3-hourly from 93 to 144

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 ENS Model:

III-i: Atmospheric fields (direct model output)

The products consist of 1 control and 50 perturbed forecasts plus the equivalent high-resolution (HRES) products. Customers can choose to receive the equivalent HRES at no extra cost. The high resolution product is suppressed beyond day 10. The fields are provided in GRIB code.

III-ii: Clusters (post-processed products)

III-iii: Probabilities (post-processed products)

The products provide the probabilities of the occurrence of instantaneous and averaged or accumulated weather events at each grid point. The products are encoded in GRIB form.

III-iv: Time series of weather parameters (post-processed products)

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.

III-v: Extreme Forecast Index (EFI) and Shift of Tails (SOT) (post-processed products)

The products provide the EFI and SOT of single level parameters calculated over 1, 3, 5 and 10-day ranges at each grid point. The products are encoded in GRIB form

III-vi: Ensemble means (post-processed products)

The fields are the means of the ensemble members at each forecast step. The fields are provided in GRIB code.

III-vii: Ensemble standard deviations (post-processed products)

The fields are the standard deviations of the ensemble members at each forecast step. The fields are provided in GRIB code.

III-viii: Tropical cyclones tracks (post-processed products)

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

The tropical cyclone trajectories are computed independently for each ensemble member; a given tropical cyclone may dissipate at different times in different members so the number of members predicting a given tropical cyclone may vary through the forecast.

 

 


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.

When requested, the invariant parameters will be provided free of information charge once with every forecast dissemination.

Base times for direct model output products: 00 UTC, 06 UTC, 12 UTC and 18 UTC  unless otherwise specified. 

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

Dissemination schedule

dissemination data stream indicator = E)

 

Based Forecast Time 06UTC

Time Available

Based Forecast time 12UTC

Time Available

Based Forecast Time 18UTC

Time Available

Based Forecast time 00UTC

Time Available

Forecast Day 0 12:40 18:40 00:40 06:40
Forecast Day 1 12:44 18:44 00:44 06:44
Forecast Day 2 12:48 18:48 00:48 06:48
Forecast Day 3 12:52 18:52 00:52 06:52
Forecast Day 10   19:20   07:20
Forecast Day 15   19:40   07:40
Derived products Step 0 to 240   19:41     07:41
Derived products Step 246 to 360   20:01   08:01

Parameters

All tables are sortable by column. Use your browser to search for specific parameters.

  Terms conventions
(inv) Invariant field. If requested these parameters can be provided free of charge

III-i:  Atmospheric model

  Product resolution
T+0h to T+360h
  • 0.2° x 0.2° lat/long grid or any multiple thereof (global or sub-area)
  • On model (Octahedral), O640 grid (global or sub-area)
  • Spectral components (TCO639) for upper-air fields (global area only)

III-i-a Atmospheric fields - single level

 

  Forecast time step Base Time
T+0h to T+90h   Hourly 00/06/12/18 UTC
T+93h to T+144h 3-hourly 00/06/12/18 UTC
T+150h to T+360h 6-hourly 00/12 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  
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  
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
~  
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  
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  
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  
sdfor 74 Standard deviation of filtered subgrid orography Climatological field (scales between approximately 3 and 22 km are included) m  
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  
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  
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)  
sr 173 Surface roughness Aerodynamic roughness length (over land). Climatological field. m  
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)  
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  
10si 207 10 metre wind speed This parameter is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth. The units of this parameter are 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.

The eastward and northward components of the horizontal wind at 10m are also available as parameters.
m s**-1  
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  
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  
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  
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  
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)  
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  
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  
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  
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  
mntpr 228227 Minimum 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 minimum 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  

III-i-b Atmospheric fields - Pressure Levels

All parameters are provided at 1000, 925, 850, 700, 500, 400, 300, 200, 100, 50, 10 hPa unless otherwise specified

  Forecast time step Base Time
T+0h to T+90h   Hourly 00/06/12/18 UTC
T+93h to T+144h 3-hourly 00/06/12/18 UTC
T+150h to T+360h 6-hourly 00/12 UTC
Short Name ID Long Name Description Units Additional information
strf 1 Stream function The horizontal wind field can be separated into divergent flow (i.e., flow that is purely divergent, with no swirl or rotation) and rotational flow (i.e., flow that is purely rotational and has no divergence).

The rotational (non-divergent) flow follows lines of constant stream function value (streamlines) and the speed of flow is proportional to the stream function gradient.

So streamlines show patterns of horizontal, rotational, air flow and the paths that particles would follow if the flow did not change with time.
m**2 s**-1  
vp 2 Velocity potential The horizontal wind field can be separated into divergent flow (i.e., flow that is purely divergent, with no swirl or rotation) and rotational flow (i.e., flow that is purely rotational and has no divergence).

This parameter is the scalar quantity whose gradient is the velocity vector of the irrotational flow. It can be used to show areas where the air is diverging (spreading out) or converging, which, depending on the vertical level, relate to ascending or descending air.
m**2 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  

III-i-c Atmospheric fields - Model Levels

   Model level parameters are produced in GRIB2 format.

Model level parameters are available from T+0h to T+168 unless otherwise specified.

  Forecast time step Base time
T+0 to T+90 hourly 00/06/12/18 UTC
T+90 to T+144 3-hourly

00/06/12/18 UTC

T+150 to T+168 6-hourly 00/12 UTC
T+168 to T+360

6-hourly

Available only for specified parameters only (see table below)

00/12 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  
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)  

III-i-d: Atmospheric fields - Potential vorticity levels

  Forecast time step Base Time
T+0h to T+90h   Hourly 00/06/12/18 UTC
T+93h to T+144h 3-hourly 00/06/12/18 UTC
T+150h to T+360h 6-hourly 00/12 UTC
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  

III-ii Clusters

This product is coded using local definition 32

Product resolution

  • 1.5° x 1.5° lat/long grid or any multiple thereof (global or sub-area)
Forecast time step Forecast ranges
T+72 to T+360 12-hourly
Short Name ID Long Name Description Units Additional information
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  

III-iii Probabilities

  Instantaneous weather events

Product resolution
  • 0.2° x 0.2° lat/long grid or any multiple thereof (global or sub-area)
  • On model (Octahedral) O640 grid (global or sub-area)
  • Spectral components (TCO639) for upper-air fields (global area only)

Probabilities -Instantaneous weather events

Forecast steps Forecasts ranges
T+24h to T+360h

24-hourly

 III-iii-a Probabilities -Instantaneous weather events - Single level

Short Name ID Long Name Description Units Additional information
10spg10 131068 10 metre Wind speed of at least 10 m/s This parameter gives the probability (in %) that the 10 m wind speed will be 10 m s-1 or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a 10 m wind speed of 10 m s-1 or above.

10 metre wind speed is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth.
%  
10spg15 131069 10 metre Wind speed of at least 15 m/s This parameter gives the probability (in %) that the 10 m wind speed will be 15 m s-1 or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a 10 m wind speed of 15 m s-1 or above.

10 metre wind speed is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth.
%  

III-iii-b: Probabilities - Averaged weather events - Single level

Short Name ID Long Name Description Units Additional information
tpl01 131064 Total precipitation less than 0.1 mm This parameter gives the probability (in %) that total precipitation will be below 0.1 mm. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting total precipitation below 0.1 mm.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. For this parameter, it is accumulated over a particular time period which depends on the data extracted.

Total precipitation 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.
%  
tprl1 131065 Total precipitation rate less than 1 mm/day This parameter gives the probability (in %) that the total precipitation rate will be less than 1 mm/day. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a total precipitation rate of less than 1 mm/day. An anomaly is a difference from a defined long-term average or climate.

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.
%  
tprg3 131066 Total precipitation rate of at least 3 mm/day This parameter gives the probability (in %) that the total precipitation rate will 3 mm/day or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a total precipitation rate of 3 mm/day or above. An anomaly is a difference from a defined long-term average or climate.

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.
%  
tprg5 131067 Total precipitation rate of at least 5 mm/day This parameter gives the probability (in %) that the total precipitation rate will 5 mm/day or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a total precipitation rate of 5 mm/day or above. An anomaly is a difference from a defined long-term average or climate.

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.
%  

III-iii-c Probabilities -Instantaneous weather events -Pressure levels

Short Name ID Long Name Description Units Additional information
talm8 131022 Temperature anomaly less than -8 K This parameter gives the probability (in %) that the temperature anomaly is below -8 K. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a temperature anomaly below -8 K. An anomaly is a difference from a defined long-term average. %  
talm4 131023 Temperature anomaly less than -4 K This parameter gives the probability (in %) that the temperature anomaly is below -4 K. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a temperature anomaly below -4 K. An anomaly is a difference from a defined long-term average. %  
tag4 131024 Temperature anomaly greater than +4 K This parameter gives the probability (in %) that the temperature anomaly exceeds +4 K. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a temperature anomaly above +4 K. An anomaly is a difference from a defined long-term average. %  
tag8 131025 Temperature anomaly greater than +8 K This parameter gives the probability (in %) that the temperature anomaly exceeds +8 K. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a temperature anomaly above +8 K. An anomaly is a difference from a defined long-term average. %  
ptsa_gt_1stdev 133093 Probability of temperature standardized anomaly greater than 1 standard deviation Probability of temperature anomaly greater than 1 standard deviation of the climatology. Climatology is derived from and updated simultaneously with the operational re-forecasts. For the computation of the probability, the closest preceding climatology to the forecast base time is used. %  
ptsa_gt_1p5stdev 133094 Probability of temperature standardized anomaly greater than 1.5 standard deviation Probability of temperature anomaly greater than 1.5 standard deviation of the climatology. Climatology is derived from and updated simultaneously with the operational re-forecasts. For the computation of the probability, the closest preceding climatology to the forecast base time is used. %  
ptsa_gt_2stdev 133095 Probability of temperature standardized anomaly greater than 2 standard deviation Probability of temperature anomaly greater than 2 standard deviation of the climatology. Climatology is derived from and updated simultaneously with the operational re-forecasts. For the computation of the probability, the closest preceding climatology to the forecast base time is used. %  
ptsa_lt_1stdev 133096 Probability of temperature standardized anomaly less than -1 standard deviation Probability of temperature anomaly less than -1 standard deviation of the climatology. Climatology is derived from and updated simultaneously with the operational re-forecasts. For the computation of the probability, the closest preceding climatology to the forecast base time is used. %  
ptsa_lt_1p5stdev 133097 Probability of temperature standardized anomaly less than -1.5 standard deviation Probability of temperature anomaly less than -1.5 standard deviation of the climatology. Climatology is derived from and updated simultaneously with the operational re-forecasts. For the computation of the probability, the closest preceding climatology to the forecast base time is used. %  
ptsa_lt_2stdev 133098 Probability of temperature standardized anomaly less than -2 standard deviation Probability of temperature anomaly less than -2 standard deviation of the climatology. Climatology is derived from and updated simultaneously with the operational re-forecasts. For the computation of the probability, the closest preceding climatology to the forecast base time is used. %  

III-iii-d Probabilities - Averaged weather events

  Forecasts step & ranges
2-day period T+120-168
3-day period T+168-240
5-day period T+120-240 T+240-360

III-iii-d:Probabilities - Averaged weather events - Pressure levels

Short Name ID Long Name Description Units Additional information
talm2 131020 Temperature anomaly less than -2 K This parameter gives the probability (in %) that the temperature anomaly is below -2 K. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a temperature anomaly below -2 K. An anomaly is a difference from a defined long-term average. %  
tag2 131021 Temperature anomaly of at least +2 K This parameter gives the probability (in %) that the temperature anomaly is 2 K or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a temperature anomaly of 2 K or above. An anomaly is a difference from a defined long-term average. %  

III-iii-e Probabilities - Daily weather events - Single level

Forecast steps & ranges

T+0-24 T+12-36  T+24-48 T+36-60 T+48-72
T+60-84 T+72-96 T+84-108 T+96-120 T+108-132
T+120-144 T+132-156 T+144-168 T+156-180 T+168-192
T+180-204 T+192-216 T+204-228 T+216-240 T+228-252
T+240-264 T+252-276 T+264-288 T+276-300 T+288-312
T+300-324 T+312-336 T+324-348 T+336-360  
Short Name ID Long Name Description Units Additional information
tpg1 131060 Total precipitation of at least 1 mm This parameter gives the probability (in %) that total precipitation will be 1 mm or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting total precipitation of 1 mm or above.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. For this parameter, it is accumulated over a particular time period which depends on the data extracted.

Total precipitation 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.
%  
tpg5 131061 Total precipitation of at least 5 mm This parameter gives the probability (in %) that total precipitation will be 5 mm or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting total precipitation of 5 mm or above.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. For this parameter, it is accumulated over a particular time period which depends on the data extracted.

Total precipitation 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.
%  
tpg10 131062 Total precipitation of at least 10 mm This parameter gives the probability (in %) that total precipitation will be 10 mm or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting total precipitation of 10 mm or above.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. For this parameter, it is accumulated over a particular time period which depends on the data extracted.

Total precipitation 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.
%  
tpg20 131063 Total precipitation of at least 20 mm This parameter gives the probability (in %) that total precipitation will be 20 mm or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting total precipitation of 20 mm or above.

In the ECMWF Integrated Forecasting System (IFS), total precipitation is rain and snow that falls to the Earth's surface. For this parameter, it is accumulated over a particular time period which depends on the data extracted.

Total precipitation 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.
%  
10fgg15 131070 10 metre wind gust of at least 15 m/s This parameter gives the probability (in %) that the 10 m gust will be 15 m s-1 or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a 10 m gust speed of 15 m s-1 or above.

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 a particular time period which depends on the data extracted.

This parameter is calculated at a height of ten metres above the surface of the Earth.
%  
10fgg20 131071 10 metre wind gust of at least 20 m/s This parameter gives the probability (in %) that the 10 m gust will be 20 m s-1 or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a 10 m gust speed of 20 m s-1 or above.

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 a particular time period which depends on the data extracted.

This parameter is calculated at a height of ten metres above the surface of the Earth.
%  
10fgg25 131072 10 metre wind gust of at least 25 m/s This parameter gives the probability (in %) that the 10 m gust will be 25 m s-1 or above. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a 10 m gust speed of 25 m s-1 or above.

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 a particular time period which depends on the data extracted.

This parameter is calculated at a height of ten metres above the surface of the Earth.
%  
tpg100 131085 Total precipitation of at least 100 mm Probability %  
tpg25 131098 Total precipitation of at least 25 mm   %  
tpg50 131099 Total precipitation of at least 50 mm   %  
10fgg10 131100 10 metre wind gust of at least 10 m/s   %  

III-iii-f Probabilities - Tropical cyclone probabilities

Forecast steps &ranges
T+24-72 T+46-96  T+72-120 T+96-144 T+120-168
T+144-192 T+168-216 T+192-240 T+216-264 T+240-288
T+216-264 T+240-288      
Short Name ID Long Name Description Units Additional information
pts 131089 Probability of a tropical storm This parameter is the potential tropical storm activity. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a tropical storm.

This parameter is calculated from the number of ensemble members that have a tropical storm within a radius of 300 km of a location, within 48 hours. This is called the 'strike probability'.

A tropical storm is a circular pattern of wind centred around an area of non-frontal low atmospheric pressure at mean sea-level that developed over the tropics or sub-tropics. Its wind speeds near the surface of the Earth are greater than 17 m s-1 and less than 32 m s-1. In the northern hemisphere it rotates in an anti-clockwise direction near the surface, and in the southern hemisphere it rotates clockwise.
%  
ph 131090 Probability of a hurricane This parameter is the potential hurricane or typhoon activity. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a hurricane or typhoon.

This parameter is calculated from the number of ensemble members that have a hurricane or typhoon within a radius of 300 km of a location, within 48 hours of the specified time. This is called the 'strike probability'.

A hurricane is a circular pattern of wind centred around an area of non-frontal low atmospheric pressure at mean sea-level that develops over the tropics or sub-tropics. Its wind speeds near the surface of the Earth are greater than 32 m s-1. In the northern hemisphere it rotates in an anti-clockwise direction near the surface, and in the southern hemisphere it rotates clockwise. In the western North Pacific it is called a typhoon.
%  
ptd 131091 Probability of a tropical depression This parameter is the potential tropical depression activity. It is derived from the range of possible outcomes as predicted by the ECMWF ensemble forecasting system. A higher probability indicates that more ensemble members are predicting a tropical depression.

This parameter is calculated from the number of ensemble members that have a tropical depression within a radius of 300 km of a location, within 48 hours of the specified time. This is sometimes called the 'strike probability'..

A tropical depression is a circular pattern of wind centred around an area of non-frontal low atmospheric pressure at mean sea-level that developed over the tropics or sub-tropics. Its wind speeds near the surface of the Earth are greater than 8 m s-1 and up to 17 m s-1. In the northern hemisphere it rotates in an anti-clockwise direction near the surface, and in the southern hemisphere it rotates clockwise.
%  

III-iv Time series of weather parameters

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 steps Product resolution

T+0h to T+360h at 6-hour intervals

  • 0.2° x 0.2° lat/long grid or any multiple thereof (global or sub-area)
  • On model (Octahedral) O640 grid (global or sub-area)
Short Name ID Long Name Description Units Additional information
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  
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  
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)  
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  

III-v Extreme Forecast Index (EFI) and Shift of Tails (SOT)

The products provide the EFI and SOT of single level parameters calculated over 1, 3, 5 and 10-day ranges at each grid point. The products are encoded in GRIB form..

Product resolution: 0.2° x 0.2° lat/long grid or any multiple thereof (global or sub-area)

 
00z
12z
1-day ranges
00Z: 00-24, 24-48, 48-72, 72-96, 96-120, 120-144, 144-168
12Z: 12-36, 36-60, 60-84, 84-108, 108-132, 132-156, 156-180
3-day ranges
00Z: 00-72, 24-96, 48-120, 72-144, 96-168, 120-192, 144-216
12Z: 12-84, 36-108, 60-132, 84-156, 108-180, 132-204, 156-228
5-day ranges
00Z: 00-120, 24-144, 48-168, 72-192, 96-216
12Z: 12-132, 36-156, 60-180, 84-204, 108-228
10-day ranges
00Z: 00-240
12Z: 00-240

III-v-a: Extreme Forecast Index (EFI) 1-day ranges 

Short Name ID Long Name Description Units Additional information
capesi 132044 Convective available potential energy shear index 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 changes rapidly with height i.e., in areas with strong vertical wind shear.

This parameter shows how extreme the ensemble forecast of convective available potential energy shear (CAPES) is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more extreme the forecast CAPES values are.
  • EFI = 0 indicates that extreme CAPES values are unlikely, although convection can still occur.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high CAPES values are expected, relative to the model climate .
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low CAPES values are expected, relative to the model climate.



See more information about the EFI . See more information about the ensemble forecast.

To help determine whether convection will be initiated or not, the probability forecast for precipitation (for example) can be used, in conjunction with this parameter.

The convective available potential energy shear (CAPES) 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.

(-1 to 1)  
wvfi 132045 Water vapour flux index Water Vapour Flux Index is a dimensionless parameter which represents the Extreme Forecast Index (EFI) of the Water Vapour Flux (wvf) averaged for a specified forecast period. It varies between -1 and 1. Shift of Tails (SOT) for wvfi is also computed and it can be retrieved by specifying type=sot. For details about wvfi please see:
Lavers, D.A., E. Zsoter, D.S. Richardson, and F. Pappenberger, 2017: An Assessment of the ECMWF Extreme Forecast Index for Water Vapor Transport during Boreal Winter. Wea. Forecasting, 32, 1667–1674, https://doi.org/10.1175/WAF-D-17-0073.1
Lavers, D. A., F. Pappenberger, D. S. Richardson, and E. Zsoter (2016), ECMWF Extreme Forecast Index for water vapor transport: A forecast tool for atmospheric rivers and extreme precipitation, Geophys. Res. Lett., 43, doi:10.1002/2016GL071320.
dimensionless  
10fgi 132049 10 metre wind gust index This parameter indicates how extreme the ensemble forecast 10 metre wind gust is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that much stronger gusts are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very calm conditions are expected, relative to the model climate.

See more information about the EFI. See more information about the ensemble forecast.

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 a particular time period which depends on the data extracted.

This parameter is calculated at a height of ten metres above the surface of the Earth.

(-1 to 1)  
capei 132059 Convective available potential energy index High values of this parameter indicate where deep 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.

This parameter shows how extreme the ensemble forecast of convective available potential energy (CAPE) is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more extreme the forecast CAPE values are.
  • EFI = 0 indicates that extreme CAPE values are unlikely, although convection can still occur.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high CAPE values are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low CAPE values are expected, relative to the model climate.

See more information about the EFI . See more information about the ensemble forecast .

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.

(-1 to 1)  
sfi 132144 Snowfall index This parameter indicates how extreme the ensemble forecast accumulated total snowfall is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  •  
  • EFI = 0 indicates an extreme event is unlikely.
  •  
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that heavy snowfall is expected, relative to the model climate.
  •  
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that little snowfall is expected, relative to the model climate.



This parameter is based on the accumulated total snow that has fallen to the Earth's surface. Snowfall is the sum of large-scale snowfall and convective snowfall. Large-scale snowfall is generated by the cloud scheme in the ECMWF Integrated Forecast System. 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. Convective snowfall 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.

See more information about the EFI. See more information about the ensemble forecast.

(-1 to 1)  
10wsi 132165 10 metre speed index This parameter indicates how extreme the ensemble forecast 10 metre wind speed is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very windy conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very calm conditions are expected, relative to the model climate.



See more information about the EFI. See more information about the ensemble forecast .

The 10 metre speed is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth.

(-1 to 1)  
2ti 132167 2 metre temperature index This parameter indicates how extreme the ensemble forecast 2 metre temperature is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low temperatures are expected, relative to the model climate.

See more information about the EFI. Seemore information about the ensemble 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.

(-1 to 1)  
mx2ti 132201 Maximum temperature at 2 metres index This parameter indicates how extreme the ensemble forecast 2 metre maximum temperature is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high maximum temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low maximum temperatures are expected, relative to the model climate.

Here, maximum temperature refers to 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.

(-1 to 1)  
mn2ti 132202 Minimum temperature at 2 metres index This parameter indicates how extreme the ensemble forecast 2 metre minimum temperature is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high minimum temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low minimum temperatures are expected, relative to the model climate.

Here, maximum temperature refers to 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.

(-1 to 1)  
tpi 132228 Total precipitation index This parameter indicates how extreme the ensemble forecast total precipitation is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very wet conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very dry conditions are expected, relative to the model climate.

Note that, because precipitation cannot be less than zero, negative values of this parameter calculated for 24-hour (short-term) precipitation do not provide sensible information (typically a dry day is not extreme/unusual). For accumulation of precipitation over longer periods (10 to 15 days for example), negative values indicate extended periods of dry weather.

See more information about the EFI. See more information about the ensemble forecast .

(-1 to 1)  

III-v-b: Extreme Forecast Index (EFI) 3, 5 and 10-day

Short Name ID Long Name Description Units Additional information
wvfi 132045 Water vapour flux index Water Vapour Flux Index is a dimensionless parameter which represents the Extreme Forecast Index (EFI) of the Water Vapour Flux (wvf) averaged for a specified forecast period. It varies between -1 and 1. Shift of Tails (SOT) for wvfi is also computed and it can be retrieved by specifying type=sot. For details about wvfi please see:
Lavers, D.A., E. Zsoter, D.S. Richardson, and F. Pappenberger, 2017: An Assessment of the ECMWF Extreme Forecast Index for Water Vapor Transport during Boreal Winter. Wea. Forecasting, 32, 1667–1674, https://doi.org/10.1175/WAF-D-17-0073.1
Lavers, D. A., F. Pappenberger, D. S. Richardson, and E. Zsoter (2016), ECMWF Extreme Forecast Index for water vapor transport: A forecast tool for atmospheric rivers and extreme precipitation, Geophys. Res. Lett., 43, doi:10.1002/2016GL071320.
dimensionless  
sfi 132144 Snowfall index This parameter indicates how extreme the ensemble forecast accumulated total snowfall is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  •  
  • EFI = 0 indicates an extreme event is unlikely.
  •  
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that heavy snowfall is expected, relative to the model climate.
  •  
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that little snowfall is expected, relative to the model climate.



This parameter is based on the accumulated total snow that has fallen to the Earth's surface. Snowfall is the sum of large-scale snowfall and convective snowfall. Large-scale snowfall is generated by the cloud scheme in the ECMWF Integrated Forecast System. 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. Convective snowfall 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.

See more information about the EFI. See more information about the ensemble forecast.

(-1 to 1)  
10wsi 132165 10 metre speed index This parameter indicates how extreme the ensemble forecast 10 metre wind speed is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very windy conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very calm conditions are expected, relative to the model climate.



See more information about the EFI. See more information about the ensemble forecast .

The 10 metre speed is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth.

(-1 to 1)  
2ti 132167 2 metre temperature index This parameter indicates how extreme the ensemble forecast 2 metre temperature is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low temperatures are expected, relative to the model climate.

See more information about the EFI. Seemore information about the ensemble 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.

(-1 to 1)  
tpi 132228 Total precipitation index This parameter indicates how extreme the ensemble forecast total precipitation is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very wet conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very dry conditions are expected, relative to the model climate.

Note that, because precipitation cannot be less than zero, negative values of this parameter calculated for 24-hour (short-term) precipitation do not provide sensible information (typically a dry day is not extreme/unusual). For accumulation of precipitation over longer periods (10 to 15 days for example), negative values indicate extended periods of dry weather.

See more information about the EFI. See more information about the ensemble forecast .

(-1 to 1)  

III-v-c: Shift of Tails (SOT) 1-day ranges

Short Name ID Long Name Description Units Additional information
capesi 132044 Convective available potential energy shear index 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 changes rapidly with height i.e., in areas with strong vertical wind shear.

This parameter shows how extreme the ensemble forecast of convective available potential energy shear (CAPES) is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more extreme the forecast CAPES values are.
  • EFI = 0 indicates that extreme CAPES values are unlikely, although convection can still occur.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high CAPES values are expected, relative to the model climate .
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low CAPES values are expected, relative to the model climate.



See more information about the EFI . See more information about the ensemble forecast.

To help determine whether convection will be initiated or not, the probability forecast for precipitation (for example) can be used, in conjunction with this parameter.

The convective available potential energy shear (CAPES) 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.

(-1 to 1)  
wvfi 132045 Water vapour flux index Water Vapour Flux Index is a dimensionless parameter which represents the Extreme Forecast Index (EFI) of the Water Vapour Flux (wvf) averaged for a specified forecast period. It varies between -1 and 1. Shift of Tails (SOT) for wvfi is also computed and it can be retrieved by specifying type=sot. For details about wvfi please see:
Lavers, D.A., E. Zsoter, D.S. Richardson, and F. Pappenberger, 2017: An Assessment of the ECMWF Extreme Forecast Index for Water Vapor Transport during Boreal Winter. Wea. Forecasting, 32, 1667–1674, https://doi.org/10.1175/WAF-D-17-0073.1
Lavers, D. A., F. Pappenberger, D. S. Richardson, and E. Zsoter (2016), ECMWF Extreme Forecast Index for water vapor transport: A forecast tool for atmospheric rivers and extreme precipitation, Geophys. Res. Lett., 43, doi:10.1002/2016GL071320.
dimensionless  
10fgi 132049 10 metre wind gust index This parameter indicates how extreme the ensemble forecast 10 metre wind gust is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that much stronger gusts are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very calm conditions are expected, relative to the model climate.

See more information about the EFI. See more information about the ensemble forecast.

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 a particular time period which depends on the data extracted.

This parameter is calculated at a height of ten metres above the surface of the Earth.

(-1 to 1)  
capei 132059 Convective available potential energy index High values of this parameter indicate where deep 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.

This parameter shows how extreme the ensemble forecast of convective available potential energy (CAPE) is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more extreme the forecast CAPE values are.
  • EFI = 0 indicates that extreme CAPE values are unlikely, although convection can still occur.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high CAPE values are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low CAPE values are expected, relative to the model climate.

See more information about the EFI . See more information about the ensemble forecast .

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.

(-1 to 1)  
sfi 132144 Snowfall index This parameter indicates how extreme the ensemble forecast accumulated total snowfall is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  •  
  • EFI = 0 indicates an extreme event is unlikely.
  •  
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that heavy snowfall is expected, relative to the model climate.
  •  
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that little snowfall is expected, relative to the model climate.



This parameter is based on the accumulated total snow that has fallen to the Earth's surface. Snowfall is the sum of large-scale snowfall and convective snowfall. Large-scale snowfall is generated by the cloud scheme in the ECMWF Integrated Forecast System. 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. Convective snowfall 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.

See more information about the EFI. See more information about the ensemble forecast.

(-1 to 1)  
10wsi 132165 10 metre speed index This parameter indicates how extreme the ensemble forecast 10 metre wind speed is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very windy conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very calm conditions are expected, relative to the model climate.



See more information about the EFI. See more information about the ensemble forecast .

The 10 metre speed is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth.

(-1 to 1)  
2ti 132167 2 metre temperature index This parameter indicates how extreme the ensemble forecast 2 metre temperature is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low temperatures are expected, relative to the model climate.

See more information about the EFI. Seemore information about the ensemble 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.

(-1 to 1)  
mx2ti 132201 Maximum temperature at 2 metres index This parameter indicates how extreme the ensemble forecast 2 metre maximum temperature is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high maximum temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low maximum temperatures are expected, relative to the model climate.

Here, maximum temperature refers to 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.

(-1 to 1)  
mn2ti 132202 Minimum temperature at 2 metres index This parameter indicates how extreme the ensemble forecast 2 metre minimum temperature is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high minimum temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low minimum temperatures are expected, relative to the model climate.

Here, maximum temperature refers to 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.

(-1 to 1)  
tpi 132228 Total precipitation index This parameter indicates how extreme the ensemble forecast total precipitation is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very wet conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very dry conditions are expected, relative to the model climate.

Note that, because precipitation cannot be less than zero, negative values of this parameter calculated for 24-hour (short-term) precipitation do not provide sensible information (typically a dry day is not extreme/unusual). For accumulation of precipitation over longer periods (10 to 15 days for example), negative values indicate extended periods of dry weather.

See more information about the EFI. See more information about the ensemble forecast .

(-1 to 1)  

III-v-d: Shift of Tails (SOT) 3, 5 and 10-day ranges

Short Name ID Long Name Description Units Additional information
wvfi 132045 Water vapour flux index Water Vapour Flux Index is a dimensionless parameter which represents the Extreme Forecast Index (EFI) of the Water Vapour Flux (wvf) averaged for a specified forecast period. It varies between -1 and 1. Shift of Tails (SOT) for wvfi is also computed and it can be retrieved by specifying type=sot. For details about wvfi please see:
Lavers, D.A., E. Zsoter, D.S. Richardson, and F. Pappenberger, 2017: An Assessment of the ECMWF Extreme Forecast Index for Water Vapor Transport during Boreal Winter. Wea. Forecasting, 32, 1667–1674, https://doi.org/10.1175/WAF-D-17-0073.1
Lavers, D. A., F. Pappenberger, D. S. Richardson, and E. Zsoter (2016), ECMWF Extreme Forecast Index for water vapor transport: A forecast tool for atmospheric rivers and extreme precipitation, Geophys. Res. Lett., 43, doi:10.1002/2016GL071320.
dimensionless  
sfi 132144 Snowfall index This parameter indicates how extreme the ensemble forecast accumulated total snowfall is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  •  
  • EFI = 0 indicates an extreme event is unlikely.
  •  
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that heavy snowfall is expected, relative to the model climate.
  •  
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that little snowfall is expected, relative to the model climate.



This parameter is based on the accumulated total snow that has fallen to the Earth's surface. Snowfall is the sum of large-scale snowfall and convective snowfall. Large-scale snowfall is generated by the cloud scheme in the ECMWF Integrated Forecast System. 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. Convective snowfall 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.

See more information about the EFI. See more information about the ensemble forecast.

(-1 to 1)  
10wsi 132165 10 metre speed index This parameter indicates how extreme the ensemble forecast 10 metre wind speed is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very windy conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very calm conditions are expected, relative to the model climate.



See more information about the EFI. See more information about the ensemble forecast .

The 10 metre speed is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth.

(-1 to 1)  
2ti 132167 2 metre temperature index This parameter indicates how extreme the ensemble forecast 2 metre temperature is, relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very high temperatures are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very low temperatures are expected, relative to the model climate.

See more information about the EFI. Seemore information about the ensemble 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.

(-1 to 1)  
tpi 132228 Total precipitation index This parameter indicates how extreme the ensemble forecast total precipitation is relative to the model climate. It is one of the ECMWF Extreme Forecast Indices (EFIs). Values range from -1 to +1.
 
  • The closer the EFI is to +1 or -1, the more likely an extreme event is.
  • EFI = 0 indicates an extreme event is unlikely.
  • EFI = +1 occurs when all the ensemble members' forecast values are above the maximum of the model climate. In this case, it means that very wet conditions are expected, relative to the model climate.
  • EFI = -1 occurs when all the ensemble members' forecast values are below the minimum of the model climate. In this case, it means that very dry conditions are expected, relative to the model climate.

Note that, because precipitation cannot be less than zero, negative values of this parameter calculated for 24-hour (short-term) precipitation do not provide sensible information (typically a dry day is not extreme/unusual). For accumulation of precipitation over longer periods (10 to 15 days for example), negative values indicate extended periods of dry weather.

See more information about the EFI. See more information about the ensemble forecast .

(-1 to 1)  

III-vi-a: Ensemble means - Single level

Short Name ID Long Name Description Units Additional information
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  
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  
10si 207 10 metre wind speed This parameter is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth. The units of this parameter are 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.

The eastward and northward components of the horizontal wind at 10m are also available as parameters.
m s**-1  
100si 228249 100 metre wind speed This parameter is the horizontal speed of the wind, or movement of air, at a height of 100 m above the surface of the Earth.

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.

Two other parameters, the eastward and northward components, can be used to give the direction of the horizontal 100 m wind.
m s**-1  

III-vi-b: Ensemble means - Pressure levels

Short Name ID Long Name Description Units Additional information
ws 10 Wind speed The speed of horizontal air movement in metres per second.

The eastward and northward components of the horizontal wind are also available as parameters.
m s**-1  
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  
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  

III-vii-a: Ensemble standard deviations - Single level

Short Name ID Long Name Description Units Additional information
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  
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  
10si 207 10 metre wind speed This parameter is the horizontal speed of the wind, or movement of air, at a height of ten metres above the surface of the Earth. The units of this parameter are 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.

The eastward and northward components of the horizontal wind at 10m are also available as parameters.
m s**-1  
100si 228249 100 metre wind speed This parameter is the horizontal speed of the wind, or movement of air, at a height of 100 m above the surface of the Earth.

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.

Two other parameters, the eastward and northward components, can be used to give the direction of the horizontal 100 m wind.
m s**-1  

III-vii-b: Ensemble standard deviations - Pressure levels

Short Name ID Long Name Description Units Additional information
ws 10 Wind speed The speed of horizontal air movement in metres per second.

The eastward and northward components of the horizontal wind are also available as parameters.
m s**-1  
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  
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  

III-viii: Tropical Cyclone tracks

  

Tropical cyclones tracks are provided in BUFR code, free of information charge. They are composed of 52 trajectories corresponding to:

  • the 50 perturbed forecasts from ENS (Ensemble Member numbers 1 to 50 in BUFR)
  • the control forecast from ENS (Ensemble Member number 51 in BUFR)
  • the HRES forecast (Ensemble Member number 52 in BUFR)

The tropical cyclone trajectories are computed independently for each ensemble member; a given tropical cyclone may dissipate at different times in different members so the number of members predicting a given tropical cyclone may vary through the forecast.

Observed (existing cyclones) and genesis (created by the forecast).

Short name Long name Description Unit Additional information
TC Tropical Cyclone     BUFR

Last updated 22-10-2020