European Centre for Medium-Range Weather Forecasts (ECMWF)/World Climate Research Program (WCRP) level III-A Global Atmospheric (TOGA) Data Sets

ECMWF created and maintains an archive of level III-A atmospheric data
in support of projects associated with the World Climate Research
Program (WCRP). This archive is directly interpolated from the ECMWF
operational, full resolution, surface and pressure level data. It is
accommodated the 10 year period beginning 1 January 1985, fulfilling
ECMWF's role as a Tropical Ocean and Global Atmosphere (TOGA) Level
III Atmospheric Data Centre.

The Level III-A archive is subdivided into three classes of data sets:

* Basic Level III
* Supplementary Fields
* Extension

The data sets are based on quantities analyzed or computed within the
ECMWF data assimilation scheme or from forecasts based on these
analyses.

The Basic Data Set contain selected analysed values in a compact form
at a resolution of 2.5 degree x 2.5degree. They are particularly suitable for
users with limited data processing resources. Derived quantities
(fluxes, etc.) are not included, but can in principle be calculated
from the data provided in the data sets.

The Supplementary Fields Data Set contains additional surface data,
fluxes and net radiation data derived from short-range forecasts used
as first-guess data for the analyses. Most of the fields in this data
set contain values accumulated over the first 6 (or 12) hours of the
forecast. The exceptions, total cloud cover fields, contain
instantaneous 6 (or 12) hour forecast values. This is a subset of the
operational first-guess surface data.

The Extension Data Set contains additional surface data, fluxes, net
radiation data and precipitation derived from 24-hour forecast
values. All the fields in this data set contain values accumulated
between time step 12 and time step 36 of the forecast.

The 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.

A full extraction service is supported, 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.

[Summary Extracted from the ECMWF home page]