Mars archiving for VarEPS/Monthly

The MARS archiving of monthly forecasting has been changed to be fully consistent with the EPS archiving. The present section describes the new archiving of the monthly forecasting system which will be used when the monthly forecasting suite becomes operational (1st quarter 2008). The differences between the"old" and the "new" way of archiving monthly forecasting data can be found here.

5.1 Monthly archive of atmospheric fields:

a) Raw data:

The IFS writes the real-time data into the ENFO (1035) stream in MARS and the hindcast into the ENFH (1033) stream in MARS. All the data are archived using their original model representation (Reduced Gaussian grid or Spherical Harmonics). The output produced by default for monthly forecasts and stored in MARS are listed here. Upper-air fields are archived every 12 hours, whereas surface fields are archived every 6 or 24 hours.

Wave model monthly forecasts are stored in the stream WAEF (1081) for the real-time forecast and in the stream ENWH (1079) for the hindcast.

For the control forecast TYPE=CF, for perturbed forecasts TYPE=PF. For the hindcast, the reference date of the hindcast (date of the real-time forecast associated to the hindcast) has to be present in the MARS request as DATE=YYYYMMDD, The actual date of hindcast is entered as HDATE=YYYMMDD.

Example of MARS request:

retrieve,
class=od,expver=9935,stream=enfo,type=pf,levtype=pl,level=500,param=Z,number=1/to/50,date=20071115,time=00,step=0/to/768/by/12, target="out"

or webmars catalogue

for the back statistics:

retrieve,
class=OD,expver=9935,stream=enfh,type=pf,levtype=PL,
level=500,param=Z,number=1/to/4,hdate=20001115,date=20071115,time=00, step=12/to/768/by/12,target="out"

or webmars catalogue

b) Weekly Means:

Monthly forecast weekly means are calculated for all atmospheric variables and stored in the stream ENFO (1035) for the real-time forecast and stream ENFH (1035) for the hindcast with type FCMEAN.

Wave model forecast means (weekly means) are calculated and stored in the stream WAEF(1081) for the real-time forecast and stream ENWH(1079) for the hindcast.

Monthly forecast weekly maximum (type FCMAX), minimum (type FCMIN) and standard deviation (type FCSTDEV) have also been calculated and archived for all surface fields.

Important note: ALL the parameters need to be written with their code table: 128 for instantaneous fields and 172 for accumulated fields. For example Geopotential should be introduced as: PARAMETER=129.128 (parameter=Z, won't work!). This is necessary since the same variables are archived in MARS with other tables for a different meaning (see in following paragraphs).

The weeks are as follows:

Week1: day 5 to day 11 (STEP=96-264)

Week2: day 12 to day 18 (STEP=264-432)

Week3: day 19 to day 25 (STEP=432-600)

Week4: day 26 to day 32 (STEP=600-768)

(In the previous version of the monthly forecasting system, weekly means was archived differently. weekly means were archived under the stream under the stream mnfm, and the weekly period were defined using the MARS parameter FCPERIOD instead of STEP. For example FCPERIOD=5-11 refered to the period day 5-11.)

Since the monthly forecast starts every Thursday at 00Z, they correspond to the week from Monday at 0Z to Sunday at midnight.

Here is an example of a MARS retrieval for weekly means from the real-time forecast:

retrieve,
class=OD,expver=9935,stream=enfo,type=fcmean,levtype=PL,
level=500,param=129.128,number=1/to/50,date=20071115,time=00,step=96-264,
target="out"

or webmars catalogue

and from the hindcast:

retrieve,
class=OD,expver=9935,stream=enfh,type=fcmean,levtype=PL,
level=500,param=129.128,number=1/to/50,date=20071115,hdate=20071015,time=00,step=96-264,
target="out"

or webmars catalogue

c) Ensemble means and standard deviation of raw data

Ensemble means and standard deviations are archived in MARS only for a limited
number of fields: temperature at 850 and 500 hPa and geopotential at 1000 and
500 hPa.

To retrieve these fields, TYPE=EM (ensemble mean) or TYPE=ES
(ensemble standard deviation). For those fields there is no need to specify the code table, since there is no possible confusion.

Example with the real-time forecast:

retrieve, class=OD,expver=9935,stream=enfo,type=em,levtype=PL, level=500,param=Z, date=20071115,time=00,step=24,target="out"

or webmars catalogue

for the hindcast, the ensemble means and standard deviations are archived under stream EFHS:

retrieve, class=OD,expver=9935,stream=efhs,type=em,levtype=PL, level=500,param=Z,date=20071115, time=00,step=768,target="out"

or webmars catalogue

It is important to note, that for the hindcast there is no date associated with the MARS request, just a reference date (DATE). For the hindcast, the ensemble mean represents the mean over the 5-member ensemble for each year of the hindcast set associated with the reference date. Since the hindcast covers 18 years, this represents the ensemble mean (or standard deviation) over 90 members.

d) Weekly mean ensemble mean and weekly mean standard deviation

Weekly mean ensemble mean and weekly mean standard deviation are archived in MARS only for a limited number of fields (see table)

To retrieve these fields, TYPE=EM (ensemble mean) or TYPE=es (ensemble standard deviation)
For those fields the code table needs to be specified (128 for instantaneous fields and 172 for accumulated fields)

Example with the real-time forecast:

retrieve, class=OD,expver=9935,stream=enfo,type=em,levtype=SFC,param=139.128, date=20071115,time=00,step=96-264,target="out"

or webmars catalogue

for the hindcast, the ensemble means and standard deviations are archived under stream EFHS:

retrieve, class=OD,expver=9935,stream=efhs,type=em,levtype=SFC, param=139.128,date=20071115, time=00,step=96-264,target="out"

or webmars catalogue

It is important to note, that for the hindcast there is no date associated to the MARS request, just a reference date (DATE). For the hindcast, the ensemble mean (standard deviation) represents the mean (standard deviation) over the 5-member ensemble for each year of the hindcast set associated with the reference date. Since the hindcast covers 18 years, this represents the ensemble mean (or standard deviation) over 90 members.

e) Weekly anomalies

The anomalies are the difference between the real-time forecast and the model climatology. The model climatology corresponds to the ensemble mean of the hindcast.

Monthly forecast weekly anomalies are written into the enfo (1035) stream in MARS. The MARS request is the same as for the weekly mean data of the real-time forecast, except that the table is now 171 for instantaneous fields and 173 for accumulated fields.

Example:

retrieve, class=OD,expver=9935,stream=enfo,type=fcmean,number=0/to/50,levtype=SFC,param=139.171, date=20071115,time=00,step=96-264,target="out"

f) Weekly anomalies ensemble means

The anomalies are the difference between the real-time forecast ensemble mean and the model climatology ensemble mean. The model climatology corresponds to the ensemble mean of the hindcast.

Monthly forecast weekly anomalies ensemble means are written into the enfo (1035) stream in MARS. The MARS request is the same as for the weekly mean ensemble mean data of the real-time forecast, except that the table is now 171 for instantaneous fields and 173 for accumulated fields.

Example:

retrieve, class=OD,expver=9935,stream=enfo,type=em,levtype=SFC,param=139.171, date=20071115,time=00,step=96-264,target="out"

g) EPSgrams

This concerns only a very limited set of surface variables: Temperature at 850 hPa, 2-metre temperature, 10 metre wind speed, total cloud cover and total precipitation.

In order to avoid retrieving 51 members for the real-time forecast or 90 members for the back statistics to create EPSgrams, several fields have been reordered, and the minimum, 25%, median, 75% and maximum of the ensemble distribution have been archived. These fields are: T850, total cloud cover, 2-metre temperature, total precipitation and 10 metre scalar wind speed.

For the real-time forecast:

To retrieve these fields: STREAM=enfo, TYPE=ED, NUMBER=1 (minimum), NUMBER=13/14
(25%), NUMBER=26 (MEDIAN), NUMBER=38/39(75%) or NUMBER=51 (MAXIMUM)

example:

retrieve,class=OD,expver=9935,stream=enfo,type=ed,number=26,levtype=PL, level=850,param=T,date=20071115,time=00,step=24,target="out"

or webmars catalogue

For the hindcast:

As for types em and es, there is no hindcast date in the MARS retrieval command for the hindcast. The reordering is made over the 90 members of the 12-year hindcast. The reference date is used in the MARS retrieval command.

To retrieve these fields: STREAM=efhs, TYPE=ED, NUMBER=1 (minimum), NUMBER=23/24
(25%), NUMBER=45/46 (MEDIAN), NUMBER=67/68(75%) or NUMBER=90 (MAXIMUM)

example:

retrieve,class=OD,expver=9935,stream=efhs,type=ed,number=45,levtype=PL, level=850,param=T,date=20071115,time=00,step=24,target="out"

or webmars catalogue

h) Forecast probabilities:

There are 2 types of forecast probabilities: anomaly events (probability for a certain variable to exceed a threshold) and probability distributions (quantiles). At present, they are available only for weekly mean anomalies.

1) Anomaly event:

Example: Probability that the weekly averaged 2m temperature weekly anomaly exceeds 2K. These probabilities are archived under stream ENFO (1035) and type EP

Each anomaly event has a specific parameter code in table 131. For instance, the probability that the weekly averaged 2m temperature anomaly exceeds 2K has the parameter code 1 in table 131. All the anomaly events and the corresponding parameter codes are listed here. The anomaly events are archived under type ep.

example:

retrieve, stream=enfo, time=00, levtype=sfc, expver=9935,
param=1.131, class=od, date=20071115, step=96-264, type=ep, target="out"

or webmars catalogue

2) Probability distribution:

Probability distribution is the probability to be in a given quantile. The quantiles are derived from the model climatology.

A new MARS keyword has been defined: quantile. The syntax is quantile=X:Y, which means quantile X out of Y.

For example, quantile=1:3 means the probability distribution in the first tercile (lower tercile).

The complete list of probability distributions is listed here

All the parameters are coded in table 131.

Example:

retrieve,stream=enfo,time=00,levtype=sfc,expver=9935,param=139.131,
quantile=1:3,class=od,date=20071115,step=96-264,type=pd,target="out"

or webmars catalogue

3) Probability boundaries:

Probability boundaries are the threshold values which define the quantiles. They are computed from the model climatologyy.

Important note: the values archived as probability boundaries are anomalies relative to the model climate. They are not computed from the raw data.

The syntax is the same as for probability distributions, except type=pb instead of type=pd.

For example, type=pb, quantile=1:3 means the boundary distribution between the lower and middle tercile.

The complete list of probability boundaries is listed here

Example:

retrieve,stream=enfo,time=00,levtype=sfc,expver=9935,param=139.171,
quantile=1:3,class=od,date=20071115,step=96-264,type=pb,target="out

or webmars catalogue

i) Significance:

Plots of monthly forecasts weekly mean anomalies (see example here) display the difference between the distribution of the real-time ensemble of weekly means and the model climatology of weekly means. In addition a statistical test (WMW-test) is performed to determine if the difference is statistically significant within the 5% level of confidence. The result of this significance test is archived under stream enfo (1035), type em and table 234.

The syntax is the same as for retrieving ensemble mean weekly means except that that the table is 234 instead of 128 or 171.

The significance is archived only for only a limited number of parameters.

The complete list of parameters is listed here

Example:

retrieve, class=OD,expver=9935,stream=enfo,type=em,levtype=SFC,param=139.234, date=20071115,time=00,step=96-264,target="out"

or webmars catalogue

5.2 Monthly archive of ocean fields:

Before 17/11/2011:

The ocean data are archived together with the atmospheric data, and are distinguished by the 'LEVTYPE' attribute, which is set to 'DEPTH' or 'DP'. Ocean variables are archived as instantaneous fields (product=inst), accumulated fields (product=tacc) or time series (product=tims). The fields are archived along horizontal (section=h), meridional (section=m) or zonal sections (section=z).

A complete list of the ocean parameters archived on MARS can be found here.

After 17/11/2011:

Since 17 November 2011, teh HOPE ocean model has been replaced by NEMO. This led to a change in the archiving of the ocean fields. The ocean fields are no longer archived in grib on MARS, They are now stored in netcdf format on ecfs at ec:/emos/0001/output/ocean/.

For each monthly integration, the 3 legs (day 0-10, day 11-15, day 16-32) are archived in separate files. For instance, for the forecast starting on 4/11/2011, the ocean files have the following names:

0001_1d_20111027_20111104_grid_T_03.nc for legA
0001_1d_20111105_20111110_grid_U_03.nc for legB
0001_1d_20111111_20111127_grid_U_03.nc for legC

The netcdf files contain the following variables:

SST
Surf Salinity
Water Flux (E-P)
Total heat flux (downward)
Solar radiation
Mixed-layer depth
Ice cover
Thermocline depth
Depth of 20 degree isotherm
Depth of 26 degree isotherm
depth of 28 degree isotherm
Wind stress (u,v)
Surface currents (u,v)

All the fields are daily for each ensemble member. All the fields are in the NEMO T grid, except for Wind stress and Surface currents (NEMO U and V grids).