Norwegian Service Centre for Climate Modelling -> ERA-40




Several climate researchers have shown an interest in the ECMWF ERA-40 reanalysis dataset. To establish a local copy for some of these data will be a natural task for NoSerC. There are, however, many options regarding which data we should prioritize. To make a local copy of the whole archive is, for the time being, not feasible. Therefore, all researchers with an interest in these data are invited to send us an overview of the variables and resolutions (time, horizontal and vertical) they would be interested in.

We have allready received a request for upper air data on the 60 model levels in a T42 resolution (corresponding to a 128x64 grid).

We plan to start downloading  ERA-40 data from October 15. Any wishes we receive before this date will be taken into consideration in our initial downloading scheme.

The storage capacity on the /noserc  disk on Gridur is just now not very large. This may set a limit on what we are able to download in the short run. This situation will hopefully improve next year.

A comprehensive description of the ERA-40 dataset can be found at Specifically, the archive plan contains the full description of which variables and resolutions are available. The current status of the project shows which years are available now from the planned period of reanalysis (1957-2001). The ERA-40 Data Availability page gives imortant information on how the data can be retrieved, data quality considerations and about a possible rerun of a part of the period. To get at the actual data, a web interface for data retrieval (requiring special access rights) is also available.

All this information is not easily absorbed, as it is spread out on several pages. The following summary gives a short overview of the most relevant information:

The data comprise analysis and forcast fields according to the following scheme:
Analysis 00 06 12 18
Forcast +3

Not all of these fields will be retained in the long run. Analysis and the +6 hour forcast data will be retained in full. Also, forcast data will be retained so that a time resolution of three hours will be available. Which of the forcast fields in addition to the +6 hour fields that will be kept, will depend on validation studies and user requirements. Only a limited set of variables will be archived from the ten-day (+240) forcasts.

The data will be archived in the T159 horizontal resolution (based on spherical harmonics) or the corresponding N80 gaussian grid (1.125 degrees across grid cells). The data retrieval software include options to reduce the horizontal resolution, and also to convert the grid to a regular latitude/longitude grid.

Upper air variables

Upper air data is available in 60 vertical model levels and 23 pressure levels (interpolated from the model levels). The upper air data comprise the following variables:
Standard upper air fields
geopotential vorticity cloud liquid water content
temperature divergence cloud ice water content
specific humidity relative humidity cloud cover
vertical velocity ozone mass mixing ratio potential vorticity

Additional accumulated fields
updraught mass flux Short wave radiative tendency
downdraught mass flux Long wave radiative tendency
updraught detrainment rate Clear sky short wave radiative tendency
downdraught detrainment rate Clear sky long wave radiative tendency
total precipitation profile u tendency
turbulent diffusion coefficient for heat v tendency
T tendency 
q tendency

Surface variables

The surface or single level fields (at N80 gaussian resolution) comprise the following variables:
sea surface temperature sea ice fraction (1 = full ice, 0 = no ice)
surface geopotential total column water
total column water vapour soil temperature level 1
soil temperature level 2 soil temperature level 3
soil temperature level 4 soil moisture level 1 (volumetric) 
soil moisture level 2 (volumetric) soil moisture level 3 (volumetric)
soil moisture level 4 (volumetric) snow depth
large-scale precipitation (accum.) convective precipitation (accum.)
snowfall (accum.) boundary layer dissipation (accum.)
surface sensible heat flux (accum.) surface latent heat flux (accum.)
Charnock parameter  mean sea level pressure
standard deviation of orography anisotropy of orography
angle of sub-grid scale orography slope of sub-grid scale orography
total cloud cover 10 metre eastward wind component
10 metre northward wind component 2 metre temperature
2 metre dewpoint downward surface solar radiation (accum.)
land/sea mask surface roughness
albedo (climate)  downward surface thermal radiation (accum.)
surface solar radiation (accum.) surface thermal radiation (accum.)
top solar radiation (accum.) top thermal radiation (accum.)
eastward component of turbulent stress (accum.) northward component of turbulent stress (accum.)
evaporation (accum.) low cloud cover
medium cloud cover high cloud cover
latitudinal component of gravity wave stress (accum.) meridional component of gravity wave stress (accum.)
gravity wave dissipation (accum.) skin reservoir content
maximum 2m temperature since last post-processing step minimum 2m temperature since last post-processing step
runoff (accum.) total column ozone
instantaneous eastward component of turbulent stress instantaneous northward component of turbulent stress
instantaneous surface heat flux instantaneous moisture flux (evaporation)
log. surface roughness length (m) for heat skin temperature
convective snowfall (accum.) large-scale snowfall (accum.)
forecast albedo forecast surface roughness
forecast log. surface roughness length (m) for heat low vegetation cover
high vegetation cover low vegetation type (table index)
high vegetation type (table index) snow temperature
snow albedo snow density
sea ice temperature layer 1 sea ice temperature layer 2
sea ice temperature layer 3 sea ice temperature layer 4
boundary layer height sunshine duration since last post-processing step
wind gusts at 10 m large-scale precipitation fraction (accum.)
top solar radiation clear sky (accum.) top thermal radiation clear sky (accum.)
surface solar radiation clear sky (accum.) surface thermal radiation clear sky (accum.)
snow evaporation (accum.) snow melt (accum.)

Ocean-wave data

Ocean-wave data generated by wave analysis and the coupled wave-model forcasts, together with some gridded altimeter data from the ERS-1 and ERS-2 satelites, are avalable for the following variables at 1.5/1.5 latitude/longitude grid:
significant wave height mean wave direction
peak period of 1d spectra mean wave period
coefficient of drag with waves significant height of wind waves
mean direction of wind waves mean period of wind waves
significant height of primary swell mean direction of primary swell
mean period of primary swell mean square slope of waves
components of the 2D wave spectra mean wave period from 1st moment
mean wave period from 2nd moment wave spectral directional width
mean wave period from 1st moment of wind waves mean wave period from 2nd moment of wind waves
wave spectral directional width of wind waves mean wave period from 1st moment of swell
mean wave period from 2nd moment of swell wave spectral directional width of swell
10m wind speed modified by wave model gridded ERS altimeter wave height6
gridded corrected ERS altimeter wave height6 gridded ERS altimeter range relative correction6


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