Mars archiving for VarEPS/monthly

A new MARS archiving for monthly forecasting has been designed to address issues linked to the operational running of the monthly forecasting suite. The present section describes the new archiving of the monthly forecasting system which will be used when the monthly forecasting suite becomes operational (7 October 2004).

5.1 Monthly archive of atmospheric fields:

a) Raw data:

The IFS writes the real-time data into the MNFC (1200) stream in MARS and the hindcast into the MNFH (1201) stream in MARS. All the data are archived using their original model representation (Reduced Gaussian grid or Spherical Harmonics). The outputs produced by default for monthly forecasts and stored on MARS are listed here. Upper-air fields are archived every 12 hours, whereas surface fields are archived every 6, 12 or 24 hours.

In order to retrieve these fields from MARS, three MARS command lines have to be added: method=1, system=2, and origin=ecmf but may change, if the monthly forecasting system is modified. Look at the System Change Notice to see which system value is valid. For the control forecast TYPE=CF, for perturbed forecasts TYPE=FC. 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: REFDATE=YYYYMMDD,

Example of MARS request:

retrieve,
class=od,expver=0001,stream=mnfc,type=fc,method=1,system=2,levtype=pl,origin=ecmf, level=500,param=Z,number=1/to/50,date=20041007,time=00,step=0/to/768/by/12, target="out"

or webmars catalogue

for the back statistics:

retrieve,
class=OD,expver=0001,stream=mnfh,type=fc,method=1,system=2,levtype=PL,origin=ecmf,
level=500,param=Z,number=1/to/4,date=19921007,refdate=20041007,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 MNFM (1206) for the real-time forecast and stream MFHM (1207) for he hindcast with type FCMEAN.

Wave model forecast means (weekly means) are calculated and stored in the stream MFWM(1209) for the real-time forecast and stream MHWM(1210) 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.

The weeks are as follow:

Week1: day 5 to day 11 (FCPERIOD=05-11)

Week2: day 12 to day 18 (FCPERIOD=12-18)

Week3: day 19 to day 25 (FCPERIOD=19-25)

Week4: day 26 to day 32 (FCPERIOD=26-32)

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 MARS retrieval for weekly means from the real-time forecast: here

retrieve,
class=OD,expver=0001,stream=mnfm,type=fcmean,method=1,system=2,levtype=PL,
level=500,param=Z,number=1/to/50,date=20041007,time=00,fcperiod=05-11,
origin=ecmf,target="out"

or webmars catalogue

and from the hindcast:

retrieve,
class=OD,expver=0001,stream=mfhm,type=fcmean,method=1,system=2,levtype=PL,
level=500,param=Z,number=1/to/4,date=19921007,refdate=20041007,time=00, fcperiod=05-11, origin=ecmf,target="out"

or webmars catalogue

c) Ensemble means and standard deviation

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).

Example with the real-time forecast:

retrieve, class=OD,expver=0001,stream=mnfc,type=em,method=1,system=2,levtype=PL, level=500,param=Z, date=20041007,time=00,step=24,origin=ecmf,target="out"

or webmars catalogue

for the hindcast:

retrieve, class=OD,expver=0001,stream=mnfh,type=em,method=1,system=2,levtype=PL, level=500,param=Z,date=off, refdate=20041007,time=00,step=24,origin=ecmf,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 (REFDATE). For the hindcast, the ensemble mean represents the mean over the 5-member ensemble for each year of the hindcast set associated to the reference date. Since the hindcast covers 12 years, this represents the ensemble mean (or standard deviation) over 60 members.

d) 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 MFAM (1208) stream in MARS. The MARS request is the same has for the raw data of the real-time forecast, with stream=MFAM instead of stream=MNFM. Wave model weekly anomalies are written into the stream MAWM (1211).

e) EPSgrams

In order to avoid retrieving 51 members for the real-time forecast or 60 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.

To retrieve these fields: STREAM=MNFC, TYPE=ED, NUMBER=0 (minimum), NUMBER=12
(25%), NUMBER=25 (MEDIAN), NUMBER=37 (75%) or NUMBER=50 (MAXIMUM)

example:

retrieve,class=OD,expver=0001,stream=mnfc,type=ed,method=1,system=2,number=25,levtype=PL, level=850,param=T,date=20041007,time=00,step=24,origin=ecmf,target="out"

or webmars catalogue

As for types em and es, there is no date in the MARS retrieval command for the hindcast. The reordering is made over the 60 members of the 12-year hindcast. The reference date is used in the MARS retrieval command.

f) 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 anomaly exceeds 2K

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, which corresponds to the acronyme 2TWA2K. All the anomaly avents and the corresponding parameter codes are listed here. The anomaly events are archived under type fp.

example:

retrieve, stream=mfam, origin=ecmf, system=2, method=1, time=00, levtype=sfc, expver=1,
param=2TWA2K, class=od, date=20050630, fcperiod=12-18/19-25/26-32/5-11, type=fp, target="out"

or webmars catalogue

2) Probability distribution:

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

A new 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

Example:

retrieve,stream=mfam,origin=ecmf,system=2,method=1,time=00,levtype=sfc,expver=1,param=167,
quantile=1:3,class=od,date=20050630,fcperiod=12-18/19-25/26-32/5-11,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.

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=mfam,origin=ecmf,system=2,method=1,time=00,levtype=sfc,expver=1,param=167,
quantile=1:3,class=od,date=20050630,fcperiod=12-18/19-25/26-32/5-11,type=pb,target="out"

or webmars catalogue

5.2 Monthly archive of ocean fields:

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 variables archived on MARS can be found here.