Data archiving

List of common output variables

You can find below the list of atmosphere and ocean common variables that has been defined for the s2d experiments. The list describes the basic set of variables that will be archived in MARS (atmosphere, in GRIB format) and ECFS (ocean, in NetCDF format) by all the s2d models. These variables are a minimum common set to ensure that some analyses, downscaling exercises and end-user applications can be carried out for all the coupled models. A longer list is also available upon request from the individual modelling centres.

Modellers also provide the land-sea mask and orography fields used in their atmospheric models.

Please, check all this information before producing your data files or retrieving the data you are interested in.

Atmosphere (GRIB format)

A set of daily and monthly variables is described below. No six-hourly data are archived. The data are coded taking into account that the integrations start at 00 GMT of the first day of the month (even those using the lagged average method to initialize the ensemble),

The daily variables are either instantaneous at 00 GMT or accumulated daily over 24 hours starting at 00 GMT. The pressure levels available are 850, 500, 200 and 50 hPa. The data are written in the model grid. Fluxes are downward positive. Maximum and minimum temperature at 2 metres are computed using four values at 6, 12, 18 and 24 GMT.

  • Pressure level fields
    • geopotential (129.128, m**2/s**2)
    • temperature (130.128, K)
    • zonal wind (131.128, m/s)
    • meridional wind (132.128, m/s)
    • specific humidity (133.128, kg/kg)
  • Surface fields
    • surface temperature (temperature of the first soil layer over land, sea surface temperature over open waters and ice temperature over ice, 139.128, K)
    • snow depth (141.128, m of water)
    • surface sensible heat flux (146.190, Ws/m**2)
    • surface latent heat flux (147.190, Ws/m**2)
    • mean sea level pressure (151.128, Pa)
    • total cloud cover (164.128, [0,1])
    • zonal component of 10m wind (165.128, m/s)
    • meridional component of 10m wind (166.128, m/s)
    • 2m temperature (167.128, K)
    • 2m dewpoint temperature (168.128, K)
    • surface downward solar radiation (169.190, Ws/m**2)
    • surface downward longwave radiation (175.190, Ws/m**2)
    • surface net solar radiation (176.190, Ws/m**2)
    • surface net longwave radiation (177.190, Ws/m**2)
    • top net solar radiation (178.190,Ws/m**2)
    • top net longwave radiation (OLR, 179.190, Ws/m**2)
    • moisture flux from the surface into the atmosphere or evaporation (182.190, m of water)
    • 2m Tmax (computed from 6-hourly data, 201.190, K)
    • 2m Tmin (computed from 6-hourly data, 202.190, K)
    • total precipitation (228.190, m of water)
    • vertically integrated volumetric soil water (229.190, m**3/m**3)

GRIB codes, suggested ECMWF local table version 2 and variable units are in the brackets.

Monthly means for all the variables listed above are computed using one value per day (at 00 GMT). However, monthly means for 2m temperature and dewpoint, total cloud cover, mean sea level pressure and 10m wind should be computed using 6-hourly data (6, 12, 18 and 24 GMT) to adequately sample the daily cycle. Monthly means for the 100 hPa level are also expected. The accumulated fields should be converted into fluxes for the monthly means, for which the units are m/s for precipitation and W/m2 for heat and radiation fields. These monthly mean rates should use the Table 2 version 172 instead of the version 190 used for the daily data.

Note: The Met Office outputs 1.5m temperature instead of 2m temperature. Both variables will be considered the same. This variable (1.5m temperature) will be coded using the 174 ECMWF local table version 2. The same applies to the corresponding maximum and minimum temperature.

Ocean (NetCDF format)

Only monthly means for both analyses and forecasts are available in the common ocean archiving. Both 3-D fields and a small set of 2-D fields are archived. Vertical sections can be derived from the 3-D fields.

The data are interpolated on a Levitus grid as defined in the ENACT conventions for field interpolation and bathymetry. The ocean output should be interpolated on a common grid, similar to the Levitus grid, using the common land-sea mask developed in the ENACT project. The grid has one degree horizontal resolution:

Longitude: from 0 to 359 by 1 deg

Latitude: from -89 to +89 by 1 deg

(there is thus a 0.5 degree latitude shift with respect to the original Levitus grids, to retain points at the equator and at the precise TAO mooring locations).

The vertical resolution is as Levitus, with 33 levels at the following depths: 0, 10, 20, 30, 50, 75, 100, 125, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1750, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500 metres.

 

Variable units are indicated in parentheses. The fields are expected to be CF-compliant. This point can be checked using the BADC CF-convention compliance checker. The 151 ECMWF local table version 2 has been used to reference the GRIB code of the variables, also in parentheses.

 

  • 3-D fields
    • potential temperature (129.151, K)
    • salinity (130.151, PSU)
    • zonal velocity (131.151, m/s)
    • meridional velocity (132.151, m/s)
    • vertical velocity (133.151, m/s)
  • 2-D fields
    • sea level (145.151, m)
    • mixed layer depth (148.151, m)
    • 20 C isotherm depth (163.151, m)
    • average potential temperature in the upper 300m (164.151, K)

Mike Davey suggested at RT1/RT2A meeting in June 2006 to update the common list of ocean variables with the ocean transports. They are expected to be computed in the ocean grid using daily model output, from which monthly means would be extracted and interpolated into the ENSEMBLES regular grid. The list of these variables is as follows (each line contains the GRIB code, the variable and the units):

    • 140.151, UV, m**2 s**-2
    • 141.151, UT, m s**-1 K
    • 142.151, VT, m s**-1 K
    • 143.151, UU, m**2 s**-2
    • 144.151, VV, m**2 s**-2