ERA40

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:

Météo-France
Département Europe et Espace
1, quai Branly
75340 PARIS CEDEX 07
France

 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:

Sophie Cloché
Laboratoire de Meteorologie Dynamique
Ecole Polytechnique
F-91128 PALAISEAU CEDEX
France
Fax : +33 1 69 33 30 49

 

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

Data type
4 times daily
Monthly mean
Surface
1979/01-2002/08
1970/01-2002/08
Pressure Level
1967/01-2002/08 1970/01-2002/08
Model Level
1983/01-1997/12 -


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 Chap2_Discretization75.gif , Chap2_Discretization20.gif , Chap2_Discretization25.gif and Chap2_Discretization30.gif , the atmosphere is divided into Chap2_Discretization50.gif layers. These layers are defined by the pressures at the interfaces between them (the `half-levels'), and these pressures are given by

Chap2_Discretization56.gif (1)



for Chap2_Discretization61.gif . The Chap2_Discretization66.gif and Chap2_Discretization71.gif are constants whose values effectively define the vertical coordinate and Chap2_Discretization114.gif is the surface pressure field.


The values of the Chap2_Discretization5.gif and Chap2_Discretization15.gif for all Chap2_Discretization99.gif are given here to allow the reconstruction of the `full-level' pressure Chap2_Discretization104.gif associated with each model level (middle of layer) from Chap2_Discretization119.gif (Chap2_Discretization109.gif )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

Long name Grib id Netcdf name
Units Dataset* Level type*
Sea ice fraction 31
ci
(0-1)
AN
SF
Mean sea level pressure 151 msl Pascal AN SF
Temperature at 2 meters 167 t2 degK AN SF
Dew point at 2 meters 168 d2 degK AN SF
Soil temperature level1
139 stl1 degK AN SF
Soil temperature level2 170
stl2
degK AN SF
Soil temperature level3 183
stl3
degK AN SF
Soil temperature level4 236
stl4
degK AN SF
Volumetric soil water level 1
39
swvl1
m**3 s**-3 AN SF
Volumetric soil water level 2
40
swvl2 m**3 s**-3 AN SF
Volumetric soil water level 3
42
swvl3 m**3 s**-3 AN SF
Volumetric soil water level 4
42
swvl4 m**3 s**-3 AN SF
Geopotentiel
129
geopt
m**2 s**-2 AN SF
10m U wind component 165 u10 m/s AN SF
10m V wind component 166 v10 m/s AN SF
Albedo 174 al -
AN SF
Surface roughness
 173 sr   m  AN  SF
Land/sea mask 172
lsm
(0,1)
AN
SF
Sea surface temperature
24
sstk
degK
AN
SF
Skin temperature
235
skt
degK
AN
SF
 Total column water
136   tcw  kg/m^2  AN  SF
Total column water vapor 137 tcwv kg/m^2 AN
SF
Snow depth 141
sd
m of water equivalent AN
SF
 Low cloud cover
186  lcc (0-1) AN SF
 Medium cloud cover
187  mcc (0-1) AN
SF
 High cloud dover
188  hcc (0-1)
AN
SF
 Total cloud cover
164  tcc (0-1) AN
SF
Total column ozone
206   tco3 kg/m^2
AN
SF
Evaporation 182 e m of water FC SF
Large scale precipitation 142 lsp m FC SF
Convective precipitation 143 cp m FC SF
Surface solar radiation 176 ssr (W/m^2)s FC SF
Surface thermal radiation 177 str (W/m^2)s FC SF
Top thermal radiation 179 ttr (W/m^2)s FC SF
Surface latent heat flux 147 slhfl (W/m^2)s FC SF
Surface sensible heat flux 146 sshfl (W/m^2)s FC SF
East /West surface stress 180 ewss (N/m^2)s FC SF
North/South surface stress 181 nsss (N/m^2)s FC SF
Downward surface solar radiation 169
ssrd
W/m^2 s FC
SF
Downward surface thermal radiation 175
strd
W/m^2 s FC
SF
Boundary layer height 159
blh
m
FC
SF
Snowfall 144
sf
m of water equivalent FC
SF
Maximum temperature during period
 201  mx2t degK FC SF
Manimum temperature during period
 202  mn2t degK FC SF
Surface solar radiation clear sky
 210  ssrc W:m^2 s
FC SF
Large scale snowfall
 240  lsf m of water equivalent
FC SF
Convective snowfall
 239  csf m of water equivalent FC SF
Runoff
 205  ro m FC SF

Pressure level

Long name Grib id Netcdf name
Units Dataset* Level type*
Geopotentiel 129 geopt m^2/s^2 AN PL
Temperature 130 ta degK AN PL
U-velocity 131 u m/s AN PL
V-velocity 132 v m/s AN PL
Vertical velocity 135 w
Pascal/s AN PL
Vorticity (relative) 138 vo s^-1 AN PL
Divergence 155 d s^-1 AN PL
Relative humidity 157 r % AN PL
 Specific humidity
 133  q Kg/Kg AN
PL
Ozone mass mixing ratio
203
o3
Kg/Kg AN
PL
 Potential vorticity
 60  pv m^2s^-1K Kg^-1  AN PL

Model level

Long name Grib id Netcdf name Units Dataset*
Level type*
Log surface pressure 152 lnsp - AN ML(1st level)
Temperature
130 t degK AN ML
Specific humidity
133 q kg/kg AN ML

*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 ECMWF data are stored on the directory: /bdd/ERA40/
  • 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

Sophie Cloché-IPSL
Ecole Polytechnique
91128 Palaiseau cedex
FRANCE
Tel: 33 (1) 69 33 51 31
mailto: Cet e-mail est protégé contre les robots collecteurs de mails, votre navigateur doit accepter le Javascript pour le voir
Dernière mise à jour : ( 26-11-2010 )