Every day, ECMWF produces various global Analyses and Forecasts and archives them in MARS. The first ECMWF numerical model in 1979 was a grid-point model with 15 levels in the vertical and a horizontal resolution of 1.875 degrees in latitude and longitude, corresponding to a grid length of 200 kilometres. A number of major changes have occurred since ECMWF's activity started:
- With the upgrade on 22 November 2016, the IFS Cycle 48r1, implemented on 27 June 2023, increased the horizontal resolution of the medium-range ensemble and its monthly extension see (ENS) from 18 to 9 km and introduced a major upgrade to the configuration of the extended-range ensemble (ENS extended): Rather than being an extension of the medium-range forecasts starting twice a week at day 15 it will be a completely separate system, running daily from 00 UTC out to day 46 with 101 members. Over the entire forecast range the resolution will remain unchanged at 36 km horizontally and 137 model levels. As a result of these configuration changes Cycle 48r1 will offer two sets of re-forecasts (=hindcasts), one for the medium range and one for the extended range.
The upgrade to IFS Cycle 47r2 on 11 May 2021 increased the vertical resolution for the ensemble (ENS, streams enfo, enfh, efov, efho) from 91 to 137 model levels, bringing it in-line with the HRES resolution.
- 5 Nov 2017: Implementation of Seasonal Forecast SEAS5
- With the upgrade on 22 November 2016, the medium-range ensemble and its monthly extension see a major upgrade in the dynamical ocean model (NEMO): the resolution is increased from 1° and 42 layers to 0.25° and 75 layers (ORCA025Z75). Furthermore, NEMO model in the dynamical ocean model (NEMO): the resolution is increased from 1° and 42 layers to 0.25° and 75 layers (ORCA025Z75). Furthermore, NEMO model version v3.4.1 with the interactive sea-ice model (LIM2) is implemented. The ocean and sea-ice components of the ENS initial conditions are provided by the new ocean analysis and reanalysis suite ORAS5, which uses the new ocean model and revised ensemble perturbation method.
- On 8 March 2016 with the introduction of cycle 41r2 the horizontal resolution was upgraded, equivalent to about 9 km for HRES and the data assimilation (the outer loop of the 4D-Var) and to about 18 km for the ENS up to day 15. The resolution of the ENS extended (day 16 up to day 46) is about 36 km. Cycle 41r2 also introduced a new reduced Gaussian grid, the octahedral grid. > Full description
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ECMWF's Ensemble Prediction System has a coupled atmospheric and wave model. On 28 November 2006 the Variable Resolution Ensemble Prediction System (VarEPS) has been introduced by extending the forecast range from 10 to 15 days with a resolution of T399L62 for day 1 to day 10 (Leg 1) and T255L62 for day 11 to day 15 (Leg 2) has been introduced by extending the forecast range from 10 to 15 days with a resolution of T399L62 for day 1 to day 10 (Leg 1) and T255L62 for day 11 to day 15 (Leg 2). On 11 March 2008 the Monthly Forecasting System, running once a week, has been integrated with the VarEPS. The new monthly forecast products were produced for the first time on 13 March 2008. On 11 March 2008 the Monthly Forecasting System, running once a week, has been integrated with the VarEPS. The new monthly forecast products were produced for the first time on 13 March 2008. With Cycle 48r1, 12 May 2015, Leg 2 was extended to 46 days (instead of 32) on Mondays and Thursday (at 00UTC) and the number of re-forecasts increased to 11 members twice per week. On 8 March 2016, Cycle 41r2, the upgraded horizontal resolution increased to about 18 km up to day 15 and about 36 km for the extended range. The resolution of the ensemble of data assimilations (EDA) is increased to 18 km. With Cycle 43r1, 22 November 2016, the resolutions of the dynamical ocean model (NEMO) increased from 1 degree and 42 layers to 0.25 degrees and 75 layers. The upgrade to IFS Cycle 47r2 on 11 May 2021 increased the vertical resolution for the ensemble (ENS, streams enfo, enfh, efov, efho) from 91 to 137 model levels.
IFS Cycle 48r1, implemented on 27 June 2023, increased the horizontal resolution of the medium-range ensemble (ENS) from 18 to 9 km and introduced a major upgrade to the configuration of the extended-range ensemble (ENS extended): Rather than being an extension of the medium-range forecasts starting twice a week at day 15 it will be a completely separate system, running daily from 00 UTC out to day 46 with 101 members. Over the entire forecast range the resolution will remain unchanged at 36 km horizontally and 137 model levels. As a result of these configuration changes Cycle 48r1 will offer two sets of re-forecasts (=hindcasts), one for the medium range and one for the extended range.
- Control forecast: an unperturbed forecast at a lower resolution than the main HRES 10-day forecast. Forecast runs to 15 days, with lower resolution from truncation step 240 onwards. Data is available on Surface, Model levels, Pressure levels and Isentropic levels.
- Calibration/Validation forecast: VarEPS includes two constant-resolution forecasts for calibration and validation purposes which run for both resolutions from day 1 - 15. Data is available on Surface, Model levels, Pressure levels and Isentropic levels.
- Perturbed forecasts: different forecasts to 10 days with perturbed initial conditions. They are numbered from 1 to N depending on the EPS setup. Data is available on the Surface and on Pressure levels and Isentropic levels.
- Initial condition perturbations: the initial conditions for the EPS are designed to represent the uncertainties inherent in the operational analysis. They are created by adding perturbations to the operational analysis which produce the fastest energy growth during the first two days of the forecast period, defined using the singular vector technique.
- Forecast probabilities: a statistical distribution of the weather parameters from all ensemble members is used to produce probabilistic weather forecasts. With the introduction of VarEPS this data type has been discontinued.
- Event probabilities: provide the probabilities of the occurrence of weather events at each grid point. The probabilities are calculated on the basis that each ensemble member is equally likely.
- Ensemble means: are means of the ensemble forecast members.
- Clusters: similar ensemble members are grouped together into clusters. The mean and standard deviation of these clusters are computed (as well as the mean and standard deviation of the overall ensemble). Five sets of clusters are computed, one for the entire European area, and four for smaller areas.
- Tubes: another clustering method which averages all ensemble members which are close to the ensemble mean and excludes members which are significantly different.
- Extreme Forecast Index (EFI): measures the difference between the probability distribution from the EPS and the model climate distribution.
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Monthly archive of atmospheric fields:Raw dataThe IFS writes its data into the MOFC (1090) stream in MARS. All of the data are archived using their original model representation (Reduced Gaussian Grid or Spherical Harmonics). Upper-air fields are archived every 12 hours, whereas surface fields are archived every 3, 6, 12 or 24 hours.
Wave model monthly forecasts are archived as stream WAMF (1095). In order to retrieve these fields from MARS, two MARS command lines have to be added: method=1, and system=2, 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. Here is an example of MARS retrieval: retrieve, class="od",expver=0001,stream=mofc,type=fc,method=1,system=2,levtype=pl, level=500,param=Z,number=1/to/50,date=20020327,time=00,step=12/to/768/by/12, target="out" Weekly MeansMonthly forecast weekly means are calculated for all atmospheric variables and stored in the stream MOFM (1094) and type FCMEAN. Wave model forecast means (weekly means) are calculated and stored in the stream WMFM (1096). 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: Week 1: day 5 to day 11 (FCPERIOD=05-11) Here is an example of MARS retrieval for weekly means: retrieve, class="od",expver=0001,stream=mofm,type=fc,method=1,system=2,levtype=pl, level=500,param=Z,number=1/to/50,date=20020327, time=00, fcperiod=05-11, target="out" Ensemble means and standard deviationEnsemble 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, stream=MOFC, TYPE=EM (ensemble mean) or TYPE=ES (ensemble standard deviation). example: class=od,expver=0001,stream=mofc,type=em,method=1,system=2,levtype=pl,level=500, param=Z,date=20020327,time=00,step=24, target="out" EPSgramsIn order to avoid retrieving 51 members 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=MOFC, TYPE=ED, NUMBER=0 (minimum), NUMBER=12 (25%), NUMBER=25 (MEDIAN), NUMBER=37 (75%) or NUMBER=50 (MAXIMUM) example: class=od,expver=0001,stream=mofc,type=ed,method=1,system=2,number=25,levtype=pl, level=500,param=Z,date=20020327,time=00,step=24, target="out" Monthly archive of ocean fields:Ocean fields in the coupled forecasts: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). Ocean fields in the accelerated forecast:Fluxes and ocean data created during the 12 days of ocean real-time forecast ( to create the ocean initial conditions) are stored on MARS under TYPE=OF (ocean fields) and FF (forcing fields).
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Stand alone Ocean Analysis
The main purpose of the ocean analysis is to provide initial conditions for the extended range forecasts (seasonal and monthly). There are two streams: The re-analysis stream spans the period 1959 up to 11 days behind real time whereas the real-time stream started in August 2006. > more information on the System 3 Ocean Analysis documentation
Monthly and climatology datasets
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BUFR (Binary Universal Form for the Representation of meteorological data) is a WMO defined format for point data (irregularly spaced), which is used for archived observations. The BUFR format is handled via BUFREX and other subroutines provided by the ECMWF BUFRDC software.
ODB
In the IFS observations are handled by ODB (Observational Data Base).
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