ECMWF 45-YEAR REANALYSIS DATA FROM NCAR

The European Centre for Medium-Range Forecasts (ECMWF) Re-Analysis (ERA-40) project has produced a comprehensive global analysis for the 45 year period covering September 1957 to August 2002. The project utilized an atmospheric model with 60 vertical levels, T159 spherical harmonic representation for the basic dynamic fields and a reduced Gaussian grid with an approximate uniform spacing of 125km for surface and other fields. The reanalysis model assimilated multiple archives of in situ and satellite observations. As a partner in the ERA-40 project, the Data Support Section (DSS) of the Scientific Computing Division (SCD) at the National Center for Atmospheric Research (NCAR) is the sole distributor of the ERA-40 data products in the United States. All project data are available from the DSS only for non-commercial research in the U.S. and some locations in Canada. The products include atmospheric model resolution analyses and forecasts, ocean wave analyses and forecasts, many parameters at lower resolution (2.5 degree latitude by longitude grids), monthly mean analyses, analyses on isentropic and potential vorticity surfaces, and special products for research in chemical transport and radiative transfer. Additional products have also been computed at NCAR. The total archive is over 33 Terabytes (TB) in size. The primary analyzed data are approximately 5 TB and have been organized into smaller product subsets to promote easier access. A web interface for each subset provides direct access for both large and small data downloads initiated in real-time. Users may also design their own subsets for some products by selecting variables, levels, and time through a web interface. These custom requests are typically processed in a delayed mode with user notification by e-mail when the data are ready. When practical, the data are transferred to the user using the web or File Transfer Protocol (FTP). The DSS can also provide data on various writeable media. The ERA-40 archive and subsets generated by DSS are provided in the World Meteorological Organization (WMO) GRIdded Binary (GRIB) data format. User software has been developed to decode, regrid, and reformat the data. A comprehensive description of the NCAR ERA-40 archive and access to the data are available at http://dss.ucar.edu/pub/era40.