A subset of reanalysis from ECMWF ERA40 is available for the IPSL scientific community on ClimServ. Products have been extracted at ECWMF on regular latitude/longitude grid and converted from GRIB (meteorological format) to Netcdf (self-describing format, widely used in modelers community).  Note that the ERA40 archive over the full period (1958-2002), with other products is also avalaible at IDRIS.

You must be a member of the IPSL to access to these data. In other cases, write a letter to:

 Introduce yourself  and request the permission to use the netCDF formatted ECMWF Dataset available at IPSL. Upon receipt of the agreement from Météo-France, fax it to:

Spatial coverage

Global area: 0E to 358.875E , 90N to 90S

regular longitude-latitude mesh: 1.125x1.125deg

Temporal resolution

•     4 times daily (4xdaily) products:

    Analysis

    Times : 0 6 12 18 h
    step : 0 h

    Forecasting

    Times : 0, 6, 12, 18 h
    Steps :6 h

• Monthly means 

Temporal coverage

Levels

Model levels

• 60 levels

The ECMWF model uses a hybrid vertical coordinate that reduces smoothly from a terrain-following sigma coordinate in the lower troposphere to a pressure coordinate in the stratosphere.

To represent the vertical variation of the dependent variables , , and , the atmosphere is divided into layers. These layers are defined by the pressures at the interfaces between them (the `half-levels'), and these pressures are given by

(1)

The values of the and for all are given here to allow the reconstruction of the `full-level' pressure associated with each model level (middle of layer) from ( )by using equation (1) and the surface pressure field.

Pressure levels

• 23 levels (in hPa) : 1, 2, 3, 5, 7, 10, 20, 30, 50, 70, 100, 150, 200, 250, 300, 400, 500, 600, 700, 775, 850, 925, 1000

The fields have been interpolated to standard pressure levels from the original model levels.  

Available products

Surface

Pressure level

Model level

*AN: Analysis
*FC: Forecats
*SF: surface
*PL: pressure level
*ML: model level

Access

The access to this dataset is restricted to the members of IPSL. 

You can access data by several ways :

• from your login on climserv server, camelot: cd /bdd/ERA40/.
  To have an access on our server, please mail to Cet e-mail est protégé contre les robots collecteurs de mails, votre navigateur doit accepter le Javascript pour le voir

• by ftp : ftp://ftp.climserv.ipsl.polytechnique.fr/era40/
• by your login at IDRIS: data are available in the /u/rech/psl/rpsl376/ERA40/NETCDF/ directory. You must be a member of the subipsl subgroup; if it is not the case, please contact Sophie Cloché ( Cet e-mail est protégé contre les robots collecteurs de mails, votre navigateur doit accepter le Javascript pour le voir )
• by OpenDaP at IDRIS (in dowload mode): http://dods.idris.fr:81/rpsl376/ERA40/NETCDF/
• by OpenDaP at IDRIS (in opendap mode):http://dods.idris.fr:81/cgi-bin/nph-dods/rpsl376/rpsl376/ERA40/NETCDF/

Format

The data files are in the netCDF format and are compatible with the CF convention. It defines the meaning of attributes, the naming of variables, the units, the coordinate variables.

The files are organized by variable,  by month for analysis and for forecast, for 4xdaily fields. For monthly means, there is one file per variable and per year. The geophysical values of variables (called unpacked values) are coded on 2 bytes (packed values).
The vast majority of the data that we distribute in netCDF files have been packed into short integers to save space. You must unpack that data to get the correct floating point representation of the data. Each netCDF variable (except some of them) that has been packed has an add_offset and scale_factor attribute associated with it. The scale_factor and add_offset can vary with each netCDF file even for the same variable from the same data set, though this doesn't happen often.

The formula to unpack the data is:

unpacked value = add_offset + ( (packed value) * scale_factor )

Related file Naming and Structure information

• The subdirectories are the following:

/FFF/XXX/AA_LL/YYYY/name_file

FFF: format (NETCDF)
XXX: is the temporal resolution (4xdaily)
AA_LL: AA is the type of data (AN for Analysis or FC for Forecast)
                 LL is the level type (SF, PL, ML)

    SF: surface
    PL: Pressure level
    ML:Model level

YYYY: year

• File names:

NAME.YYYY[MM].ABC.EXT

NAME: is the netcdf parameter name (see table)
YYYY: year
MM: month
A: type(a: analysis, f:forecast)
B: level type (s:surface,v: surface pv, t: isentropic level, p: pressure level, m: model level)
C: temporal resolution (h: 4 x daily, d: daily mean, m: monthly mean)
EXT: format (.nc forNetcdf)

Original source

European Centre for Medium-Range Weather Forecasts.

Usage restrictions

The ECMWF  data are restricted to non-commercial use. For additional information or permission to use ECMWF data, contact the European Centre for Medium-Range Weather Forecasts

Contact