ECMWF 40 Year Re-analysis (ERA-40) Data Archive

The re-analysis project ERA-40 will cover the period from mid-1957 to mid-2002, overlapping the earlier ECMWF re-analysis, ERA-15, 1979 to 1993.

The whole period from September 1957 to August 2002 is now available.

The Level III-B archive is subdivided into four classes of data sets:

• Basic 2.5° atmospheric
• Full Resolution atmospheric
• Wave
• Atmospheric Monthly Means

The data sets are based on quantities analysed or computed within the ERA-40 data assimilation scheme or from forecasts based on these analyses.

Basic 2.5° atmospheric

• These Data Sets contain values in a compact form at a resolution of 2.5° x 2.5°.
• They are particularly suitable for users with limited data processing resources.
• Much of this data is available from the ECMWF Data Server at no charge for research usage.
• All the ERA-40 data from the Data Server can be supplied by ECMWF Data Services as described.

Full Resolution atmospheric

• These Data Sets provide access to most of the data from the ERA-40 atmospheric model archived at ECMWF.
• They have a higher space resolution. They should only be used where high resolution is essential; in this respect they are particularly suited for use in conjunction with case studies and as initial conditions for high resolution models.
• They include analysis, forecast accumulation and forecast data.
  • Analysis data are available for surface, pressure, model, isentropic and potential vorticity levels.
  • Daily forecast data are available for surface, pressure and model levels.

Wave

• These Data Sets contain analysis and forecast data from the ERA-40 wave model.

Atmospheric Monthly Means

• The Atmospheric Monthly Means Data Sets provide monthly means and monthly means of daily means of analysis and forecast data.
• Analysis data are available for surface, pressure, model, isentropic and potential vorticity levels.
• Daily forecast data are available for surface, pressure and model levels.

The ERA-40 archive is currently maintained using the WMO FM 92-IX Ext GRIB (grid in binary) form of data representation, with ECMWF local versions of GRIB Table 2. All fields of data are global within the archive except for Mediterranean wave model data.

Data are stored in FM 92 GRIB using sufficient bits to ensure that the grid point values can be retrieved to an accuracy consistent with the analysis methods used

A full extraction service is provided, enabling users to obtain sub-areas of data and data at various resolutions on regular Gaussian or latitude/longitude grids, or as spherical harmonics with selected triangular truncation. All extracted data are delivered using the GRIB representation.