ERA-20C
A subset of the new reanalysis from ECMWF, ERA-20C is available for the IPSL scientific community on ClimServ. ERA-20C is ECMWF's first atmospheric reanalysis of the 20th century, from 1900-2010. It assimilates observations of surface pressure and surface marine winds only. Products have been extracted at ECWMF on regular latitude/longitude grid (at the nominal resolution of 1.125°) and converted from GRIB (meteorological format) to Netcdf (self-describing format, widely used in modelers community).  Note that the ERA-20C archive is also avalaible at IDRIS and TGCC.

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

Thierry Desponts
Météo-France DP/SERV/ACO
42, avenue Gaspard Coriolis
31057 Toulouse Cedex
Tel : +33 5 61 07 80 85
Fax: +33 5 61 07 80 79
e-mail : Cet e-mail est protégé contre les robots collecteurs de mails, votre navigateur doit accepter le Javascript pour le voir

 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 51 31

 

Spatial coverage

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

regular longitude-latitude mesh: 1.125x1.125 deg

Temporal resolution

  •     4 times daily (4xdaily) for Analysis parameters:

    Times : 0 6 12 18 h
    step : 0 h

   

  •     9 times daily  for forecats parameters:

    Times : 6 h

    step : 3,6,9,12,15,18,21,24,27 h

   

Temporal coverage

The available years are the entire period: 1900-2010.


Levels



Pressure levels

  • 37 levels (in hPa) : 1, 2, 3, 5, 7, 10, 20, 30, 50, 70, 100, 125, 150,175,  200,225,  250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 775, 800, 825, 850, 875, 900, 925, 950, 975, 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
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 vapor 137 tcwv kg/m^2 AN
SF
Snow depth 141
sd
m of water equivalent AN
SF
Total cloud cover
164  tcc (0-1) AN
SF
High cloud cover
188  hcc (0-1) AN
SF
Medium cloud cover
187  mcc (0-1) AN
SF
Low cloud cover
186  lcc (0-1) AN
SF
Snow density
33  rsn kg/m^3 AN
SF
Surface Pressure
134  sp Pa AN
SF
Surface Solar Radiance downward
169  ssrd W/m^2 s FC
SF
Surface Thermal Radiance downward
175  strd W/m^2 s FC
SF
Total precipitation
228  tp m of water equivalent FC
SF
Snowfall
144  sf m of water equivalent 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


*AN: Analysis
*SF: surface
*PL: pressure level



Access

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

You can access ERA-20C data, in NETCDF and/or GRIB format,  by several ways :

  • NETCDF, from your login on ClimServ server: cd /bdd/ERA20C/.
    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
  • NETCDF, by ftp (filtered by IPSL IP address) : ftp://ftp.climserv.ipsl.polytechnique.fr/era20c/
  • GRIB and NETCDF,  with your login at IDRIS: data are available on ERGON,  in the /arch/home/rech/psl/rpsl376/ERA20C/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 )
  • NETCDF, by OpenDaP at IDRIS (in download mode): http://dods.idris.fr:81/rpsl376/ERA20C/NETCDF/
  • NETCDF,  by OpenDaP at IDRIS (in opendap mode):http://dods.idris.fr:81/cgi-bin/nph-dods/rpsl376/ERA20C/NETCDF/
  • GRIB and NETCDF, on CEA computer TGCC (contact : Anne Cozic at LSCE)

 

Format

The data files are available 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  for 4xdaily fields and by day for forecast fields. 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/ERA20C/
  • The subdirectories are the following:

/FFF/GEO/XXX/AA_LL/YYYY/[MM]/name_file

FFF: format (NETCDF)

GEO: is the geographical area and the associated resolution: GLOBAL_RESOL

RESOL:  1125 

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

MM: month 

  • File names:

NAME.YYYY[MM].ABCe2.GEO_RESOL.EXT

NAME: is the netcdf parameter name (see table)
YYYY: year
MM: month
A: type(a: analysis, f:forecast)
B: level type (s:surface,p: pressure level, m: model level)
C: temporal resolution (h:  daily, d: daily mean, m: monthly mean)

GEO_RESOL= GLOBAL_1125
EXT: format (.nc for Netcdf)

 

Original source

European Centre for Medium-Range Weather Forecasts.

More informations on ERA-20C: 

http://www.ecmwf.int/en/research/climate-reanalysis/era-20c  

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

Citation

Users of the ECMWF data sets are requested to reference the source of the data in any publication, e.g. "ECMWF ERA-20C data used in this study/project have been provided by ECMWF with the support of the ESPRI/IPSL team". 

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 : ( 08-12-2015 )