Page History

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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title	earlier changes

In Apr 2015 with cycle 41r1 the domain of the limited-area ocean wave model has been extended to the full globe and is now referred to as HRES-SAW. The ENS configuration has been changed and new climate files have been introduced. > Full description
In

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June 2013 IFS cycle 38r2 introduced higher vertical resolution

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title	earlier changes

In June 2013 IFS cycle 38r2 introduced higher vertical resolution in the high-resolution (in the high-resolution (T1279) forecast and data assimilation of the operational runs at 00 and 12 UTC (HRES) as well as the 06 and 18 UTC cycles of the Boundary Conditions (BC) optional programme. The number of model levels increases from the current 91 levels (L91) to 137 levels (L137).In January 2010 the horizontal resolution of the deterministic model has been increased to T1279. The resolution of the EPS went up to T639/T319 for Leg A/B, respectively.
In March 2008 VarEPS and monthly forecasting were combined into a single system. On Thursday of each week, the 00 UTC VarEPS forecast are extended from 15 to 32 days at a resolution of T255 L62 with ocean coupling introduced from day 10.
In March 2007 the operational seasonal forecasting system has been upgraded from System 2 to System 3 and integrated in the Multi-Model Seasonal Forecast stream. The resolution of the atmospheric model has been increased to T159L62.
In November 2006 the EPS has been upgraded to Variable Resolution Ensemble Prediction System (VarEPS). In particular, the forecast range was extended to 15 days using the VarEPS system with a resolution of T399 L62 for day 1 to day 10 and T255 L62 for day 11 to day 15.
In February 2006 the resolution of the deterministic model has been increased to T799 and 91 model levels. The resolution of the Ensemble Prediction System (EPS) went up to T399 and 62 model levels.
In June 2004, the Early Delivery Forecasting System was implemented, comprising two main 6-hour 4d-Var analysis and forecast cycles for 00 and 12 UTC and two additional 12-hour 4d-Var analysis and first guess forecast cycles.
In November 2000, the spectral truncation was extended to wave number 511.
In September 2000, 4d-Var cycling was increased to 12 hours. Type First Guess has been discontinued.
In October 1999, the number of levels was increased to 60.
In October 1999, the number of levels was increased to 60.
In March 1999, the number of levels was increased to 50.
In June 1998, the atmospheric model and the wave model were coupled in order to take advantage of the boundary conditions they represent to each other.
In April 1998, the spectral truncation was extended to wave-number 319.
In November 1997, 4d-Var (four-dimensional variational Analysis) became operational.
In 1992, a wave model used for ocean wave forecasting (the WAM model) became operational, followed after a few months by a Mediterranean implementation.
In December the Ensemble Prediction System (EPS) with 32 members and a resolution of T63L31 became operational.
In September 1991, a much higher resolution spectral model was put into operation. The spectral truncation was extended to wave-number 213 and the number of levels was increased to 31 (i.e. T213L31).
In May 1985, the spectral truncation was extended to wave-number 106. The number of levels was increased to 19 in 1986.
In April 1983, the grid-point model was replaced by a T63 spectral model (i.e. a spectral representation in the horizontal with a triangular truncation at wave-number 63). The number of levels in the vertical was increased to 16.

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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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title	more information

Monthly archive of atmospheric fields:

Raw data

The 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.

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title	Complete list of atmospheric fields

Upper-air fields (archived every 12 hours):

129	Geopotential	1000	925	850	700	500	-	-	200	(also MEAN of each level)
130	Temperature	1000	925	850	700	500	400	300	200	(also MEAN of each level)
138	Vorticity (relative)	1000	925	850	700	500	-	-	200	(also MEAN of each level)
155	Divergence	1000	925	850	700	500	-	-	200	(also MEAN of each level)
133	Specific humidity (gridpoint)	1000	925	850	700	500	-	-	200	(also MEAN of each level)

60

Potential vorticity on the 330K isentropic surface

MEAN

03

Potential temperature on the 2E-6 potential vorticity surface

MEAN

Surface fields:

The following surface field is archived every 3 hours (1 field):

164

Total cloud cover

MEAN/MAX/MIN/SD

The following surface fields are archived every 6 hours (11fields):

39	Volumetric soil water layer 1	MEAN/MAX/MIN/SD
49	Wind gust at 10m	MEAN/MAX/MIN/SD
139	Soil temp level 1	MEAN/MAX/MIN/SD
142	Large scale precipitation	MEAN/MAX/MIN/SD
143	Convective precipitation	MEAN/MAX/MIN/SD
144	Snow fall	MEAN/MAX/MIN/SD
159	Boundary layer height	MEAN/MAX/MIN/SD
165	10 metre u wind component	MEAN/MAX/MIN/SD
166	10 metre v wind component	MEAN/MAX/MIN/SD
167	2 metre temperature	MEAN/MAX/MIN/SD
168	2 metre dewpoint temperature	MEAN/MAX/MIN/SD

The following surface field is archived every 12 hours (1 field):

151

Mean sea level pressure

MEAN/MAX/MIN/SD

The following surface fields are archived every 24 hours (19 fields):

40	Volumetric soil water layer 2	MEAN/MAX/MIN/SD
41	Volumetric soil water layer 3	MEAN/MAX/MIN/SD
42	Volumetric soil water layer 4	MEAN/MAX/MIN/SD
141	Snow depth	MEAN/MAX/MIN/SD
146	Surface sensible heat flux	MEAN/MAX/MIN/SD
147	Surface latent heat flux	MEAN/MAX/MIN/SD
169	Surface solar radiation downwards	MEAN/MAX/MIN/SD
170	Soil temp level 2	MEAN/MAX/MIN/SD)
175	Surface thermal radiation downwards	MEAN/MAX/MIN/SD
176	Surface solar radiation	MEAN/MAX/MIN/SD
177	Surface thermal radiation	MEAN/MAX/MIN/SD
178	Top solar radiation	MEAN/MAX/MIN/SD
179	Top thermal radiation	MEAN/MAX/MIN/SD
180	East/West surface stress	MEAN/MAX/MIN/SD
181	North/South surface stress	MEAN/MAX/MIN/SD
182	Evaporation	MEAN/MAX/MIN/SD
189	Sunshine duration	MEAN/MAX/MIN/SD
201	Max 2m temperature since last postprocessing	MEAN/MAX/MIN/SD
202	Min 2m temperature since last postprocessing	MEAN/MAX/MIN/SD

The following field is archive only at step=0 and for the control forecast (type=cf):

172

Land/sea mask

The following derived fields are not archived directly, but their monthly statistics are calculated:

207	10m scalar wind speed	MEAN/MAX/MIN/SD
228	Total precipitation	MEAN/MAX/SD

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 Means

Monthly 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)
Week 2: day 12 to day 18 (FCPERIOD=12-18)
Week 3: day 19 to day 25 (FCPERIOD=19-25)
Week 4: day 26 to day 32 (FCPERIOD=26-32)

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 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, 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"

EPSgrams

In 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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title	Complete list of ocean fields

Monthly archive of ocean fields:

Ocean data is output in different sections, H = horizontal, Z = zonal, M = meridional. There are also sections that include the time dimension: Z=longitude-time, M=latitude-time and V=depth-time. Each of these sections is a two-dimensional field, with a particular orientation in space and time. Each forecast ensemble member archives the output listed below. The ocean data is archived together with the atmosphere data, and is distinguished by the 'LEVTYPE' attribute, which is set to 'DEPTH' or 'DP'.

The following instantaneous fields are written every 24 hours. They should allow a rough estimate of drift in the ocean, and give a snapshot of any numerical problems.

Horizontal fields are:

Section	Code	Depth	Name
H	129	5/425	Potential temperature
H	130	5/425	Salinity
H	131	5	u-velocity
H	132	5	v-velocity
H	145	0	Sea-level
H	148	0	Mixed-layer depth
H	133	225	w-velocity

Vertical zonal sections are:

Section	Code	Latitude	Name
Z	129	0	Potential temperature
Z	130	0	Salinity
Z	131	0	u-velocity
Z	132	0	v-velocity
Z	133	0	w-velocity

Vertical meridional sections are:

Section	Code	Longitude	Name
M	129	220	Potential temperature
M	130	220	Salinity
M	131	220	u-velocity
M	132	220	v-velocity
M	133	220	w-velocity

The following accumulated fields are written once per month during the forecasts. Monthly means can be derived from them. They are the main fields for diagnosing the oceanic behaviour of the coupled model forecasts.

Accumulated horizontal fields are:

Section	Code	Depth	Name
H	129	5	Potential temperature
H	130	5	Salinity
H	131	5	u-velocity
H	132	5	v-velocity
H	145	0	Sea level
H	148	0	Mixed layer depth
H	163	0	Depth of 20 deg isotherm
H	164	0	T averaged over upper 300m
H	175	0	S averaged over upper 300m
H	153	0	Zonal wind stress
H	154	0	Meridional wind stress
H	156	0	Net surface heat flux
H	157	0	Absorbed solar radiation
H	158	0	Precipitation - Evaporation

Accumulated vertical zonal sections are:

Section	Code	Latitude	Name
Z	129	0	Potential temperature
Z	130	0	Salinity
Z	131	0	u-velocity
Z	133	0	w-velocity

Accumulated vertical meridional sections are:

Section	Code	Longitude	Name
M	129	60E/90E/165E/180/140W/95W/30W/10W	Potential temperature
M	130	60E/90E/165E/180/140W/95W/30W/10W	Salinity
M	131	60E/165E/140W/30W	u-velocity
M	132	60E/165E/140W/30W	v-velocity
M	133	60E/165E/140W/30W	w-velocity
M	138	60E/165E/140W/30W	Potential density

Several so-called time series fields are also produced. These allow detailed examination of the evolution of certain fields along given lines of latitude or longitude. In all cases the temporal resolution is daily.

Lines of latitude are:

Section	Code	Depth	Latitude	Name
Z	129	5	0	Potential temperature
Z	131	5	0	U velocity
Z	145	0	0	Sea level
Z	163	0	0	Depth of 20 deg isotherm
Z	153	0	0	Zonal wind stress
Z	164	0	8N/5N/0/5S/8S	T averaged over upper 300m

Lines of longitude are:

Section	Code	Depth	Longitude	Name
M	129	5	180/60W	Potential temperature
M	145	0	180/60W	Sea level
M	148	0	180/60W	Mixed layer depth

Finally, a small selection of instantaneous fields is output daily, to allow study of the evolution of the system on synoptic timescales. The fields concerned are:

Section	Code	Depth	Name
H	129	5	Potential temperature
H	145	0	Sea level
H	148	0	Mixed layer depth
M	129	0	Potential temperature

Monthly archive of ocean fields (accelerated forecast):

Since the ocean analysis lags about 12 days behind real time, the ocean model is integrated from the last ocean analysis forced by analysed wind stress, heat fluxes and P-E. During this "ocean forecast", the sea surface temperature is relaxed towards persisted SST, with a damping rate of 100W/m²/K.

Forcing fields (TYPE=FF):

The time-averaged fields used to force the ocean during the 12 days of ocean integration are archived on MARS:

Section	Code	Depth	Name
H	157	0	Absorbed solar radiation
H	161	0	Diagnosed sea surface temperature error
H	162	0	Heat flux correction
H	156	0	Net surface heat flux
H	129	0	Ocean potential temperature
H	158	0	Precipitation-evaporation
H	159	0	Specified sea-surface temperature
H	160	0	Specified surface heat flux
H	153	0	u stress
H	154	0	v stress

Ocean Fields (TYPE=OF):

Same fields as for the operational ocean analysis. The list includes all the fields stored during coupled integrations but with a much larger number of levels, longitude and latitude lines.

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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Key

Monthly archive of atmospheric fields:

Raw data

Upper-air fields (archived every 12 hours):

Surface fields:

Weekly Means

Ensemble means and standard deviation

EPSgrams

Monthly archive of ocean fields:

Ocean fields in the coupled forecasts:

Ocean fields in the accelerated forecast:

Monthly archive of ocean fields:

Stand alone Ocean Analysis

Monthly and climatology datasets

ODB