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ERA40 T85 6-hourly Surface Analysis and Surface Forecast Fields, created at NCAR

| DOI: 10.5065/D6FJ2DTZ

This historical dataset is recommended for ancillary use only and not as a primary research dataset. It has likely been superseded by a newer, improved dataset.


DS124.0 represents a dataset implemented and computed by NCAR's Data Support Section, and forms an essential part of efforts undertaken in late 2004, early 2005, to produce an archive of selected segments of ERA-40 on a standard transformation grid.

In this case, forty six ERA-40 6-hourly surface and single level analysis variables were transformed from a reduced N80 Gaussian grid to a 256 by 128 regular Gaussian grid. All fields were transformed using routines from the ECMWF EMOS library, including 10 meter winds which were treated as scalars because of a lack of 10 meter spectral vorticity and divergence. A missing value occurs in the sea surface temperature and sea ice fields to mask grid points occurring over land. Fields formerly archived as whole integers, such as vegetation indices and cloud cover, occur as integers plus a fractional part in the T85 version due to interpolation.

In addition, twenty seven ERA-40 6-hourly surface and single level 6-hour forecast variables were transformed from a reduced N80 Gaussian grid to a 256 by 128 regular Gaussian grid. All variables are valid 6 hours after the forecast was initiated. Thus, 00Z 6-hour forecast evaporation is valid at 06Z. Four of the variables are "instantaneous" variables, and the remaining twenty three variables are "accumulated" over the 6-hour forecast time. Divide the accumulated variables by 21600 seconds to obtain instantaneous values. (Multiplication by minus one may also be necessary to match the sign convention one is accustomed to.) All fields were transformed using routines from the ECMWF EMOS library, including three pairs of stresses which were treated as scalars because of a lack of spectral precursors.

The choice of a T85 Gaussian grid was based on considerations of limiting the volume of new data generated to a moderate level, and to match the horizontal resolution of the Community Atmosphere Model (CAM) component of NCAR's Community Climate System Model (CCSM).

The ERA-Interim data from ECMWF is an update to the ERA-40 project. The ERA-Interim data starts in 1989 and has a higher horizontal resolution (T255, N128 nominally 0.703125 degrees) than the ERA-40 data (T159, N80 nominally 1.125 degrees). ERA-Interim is based on a more current model than ERA-40 and uses 4DVAR (as opposed to 3DVAR in ERA-40). ECMWF will continue to run the ERA-Interim model in near real time through at least 2010, and possibly longer. This data is available in ds627.0.

Temporal Range:
1957-09-01 00:00 +0000 to 2002-08-31 18:00 +0000 (Entire dataset) Period details by dataset product
Usage Restrictions:

Downloading/Accessing data from this dataset implies acceptance of ECMWF's Terms of Use

Air Temperature Albedo Albedo Cloud Frequency
Dew Point Temperature Evaporation Gravity Wave Heat Flux
Ice Extent Incoming Solar Radiation Longwave Radiation Outgoing Longwave Radiation
Planetary Boundary Layer Height Precipitation Amount Runoff Sea Level Pressure
Sea Surface Temperature Shortwave Radiation Skin Temperature Snow
Snow Density Snow Depth Snow/Ice Temperature Snow/Ice Temperature
Snow Melt Soil Moisture/Water Content Soil Temperature Surface Roughness
Surface Winds Terrain Elevation Total Precipitable Water Tropospheric Ozone
Vegetation Cover Vegetation Species Water Vapor Wind Stress
Data Contributors:
Research Data Archive, Computational and Information Systems Laboratory, National Center for Atmospheric Research, University Corporation for Atmospheric Research
European Centre for Medium-Range Weather Forecasts
Total Volume:
313.04 GB (Entire dataset) Volume details by dataset product
Data Formats:
Related RDA Datasets:
ERA-Interim Project
More Details:
View a more detailed summary of the data, including specific date ranges and locations by parameter
Metadata Record:
Data License:
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