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2.1 Atmosphere and land surface

Detailed documentation:

2.1 Ocean and cryosphere

Detailed documentation:

4. Forecast system and re-forecasts

Note, the ECMWF seasonal forecasts cover two time ranges: the long range (LR) forecasts out to 7 months, and annual range (AR) forecasts out to 13 months. The model used for these forecasts is identical, but they have different numbers of forecast members.

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monthly (LR)

quarterly (AR)

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15 (AR)

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25 (LR)

15 (AR)

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3. Initial conditions and perturbations

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3.1

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Atmosphere

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Re-forecast

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Forecast

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Atmosphere initialization	ERA-Interim

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	ECMWF Operations
Atmosphere IC perturbations	Ensemble data assimilation and leading singular vectors applied to upper air variables	Ensemble data assimilation and leading singular vectors
Land Initialization

(Re-forecast/Forecast)

	ERA-Interim land (43r1)

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	ECMWF Operations
Land IC perturbations
Soil moisture inititialization	ERA-Interim	ECMWF operations
Snow initiialization	ERA-Interim	ECMWF operations
Unperturbed control forecast?	Yes	Yes

Data assimilation method for control analysis: 4D Var (atmosphere) and 3DVAR (ocean/sea-ice)

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Perturbations to sea surface temperature? Yes (5-member ensemble of ocean analyses/re-analyses)

Is there an unperturbed control forecast included?: Yes

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Is there horizontal and/or vertical interpolation of initialization data onto the forecast model grid?  If so, please give original data resolution(s). Yes horizontal interpolations. For soil moisture the interpolation is standardized on soil moisture index (to account for different soil texture in input and target resolution grid).

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Is the soil temperature initialized consistently with soil moisture (frozen soil water where soil temperature ≤0°C) and snow cover (top layer soil temperature ≤0°C under snow)? Both the top soil temperature and the snow temperature (if present) are initialized.

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3.2 Ocean initial conditions

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2.2 Ocean initial conditions

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4. Model Uncertainties perturbations:

5.

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Forecast system and re-forecasts

Note, the ECMWF seasonal forecasts cover two time ranges: the long range (LR) forecasts out to 7 months, and annual range (AR) forecasts out to 13 months. The model used for these forecasts is identical, but they have different numbers of forecast members.

6

Perturbations to sea surface temperature? Yes (5-member ensemble of ocean analyses/re-analyses)

Perturbation to soil moisture? Yes (EDA)

Perturbation to surface stress or roughness? No (generated by wave model)

Any other surface perturbation? No

Are the above surface perturbations applied to the Control forecast? NA

Additional comments

6. Other details of the models:

Description of model grid: Cubic octohedral grid

List of model levels in appropriate coordinates: http://www.ecmwf.int/en/forecasts/documentation-and-support/91-model-levels

What kind of large scale dynamics is used?  Spectral semi-lagrangian

What kind of boundary layer parameterization is used? Moist EDMF with Klein/Hartmann stratus/shallow convection criteria

What kind of convective parameterization is used? Tiedtke 89, Bechtold et al 2004 (QJ)

What kind of large-scale precipitation scheme is used?

What cloud scheme is used? Tiedtke 91 prognostic cloud fraction

What kind of land-surface scheme is used? HTESSEL

How is radiation parametrized? CY41R2 Official IFS Documentation

Other relevant details?

7. Re-forecast Configuration

Number of years covered: 20 past years

Produced on the fly or fix re-forecasts? On the fly

Frequency:   Produced on the fly twice a week to calibrate the Monday and Thursday 00Z real-time forecasts. The re-forecasts  consists of a 11-member ensemble starting the same day and month as the Thursday real-time forecasts for the past 20 years.

Ensemble size: 11 members

Initial conditions: ERA interim (T255L60) + Soil reanalysis (Tco639) + ORAS5 ocean initial conditions (0.25 degree)

Is the model physics and resolution  the same as for the real-time forecasts: Yes

If not, what are the differences: NA

Is the ensemble generation the same as for real-time forecasts? Yes. Except for EDA perturbations which are taken from the most recent year.

If not, what are the differences: NA

Other relevant informations:

ECMWF re-forecasts are produced on the fly. This means that every week a 2 new set of re-forecasts are produce to calibrate the Monday and Thursday real-time ensemble forecasts of the following week using the latest version of IFS. The ensemble re-forecasts consist of a 11-member ensemble starting the same day and month as a real-time forecast (Monday and Thursday), but covering the past 20 years. For instance the first re-forecast set archived in the S2S database with this new version of the ECMWF model was the re-forecast used to calibrate the real-time forecast of 14  May 2015 (a Thursday).  This set consisted of a 11-member ensemble starting on 1st January 1995, 1st January 1996, ... 1st January 2014 (20 years, 11 member ensemble = 220-member climate ensemble). The re-forecast dataset is therefore updated every week in the S2S archive.

The ECMWF re-forecasts are archived in the S2S database using two dates: "date" and "hdate" (see examples below): hdate is the actual date of the re-forecast (e.g. 19950101) while date is the date of the real-time forecast (=ModelversionDate in grib2) associated to the re-forecast (20150101). The reason we need 2 dates is because the ECMWF re-forecasts are produced on the fly and we need to avoid the re-forecasts produced in the future years to overwrite the re-forecasts currently produced. Therefore ModelversionDate  allows us to distinguish the re-forecasts produced in 2015 from those produced in 2016, 2017...

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. References: