Globally-gridded atmospheric research-quality time series data from the Goddard Earth Observing System - Data Assimilation System (GEOS-DAS) is scheduled to be public distribution at the Distributed Active Archive Center (DAAC) located within the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) in late 2001. The Data Assimilation Office (DAO) at the Goddard Space Flight Center will continue to produce this near real-time data set in direct support of the operational EOS instrument product generation for the Terra (12/1999 launch), Aqua (01/2002 launch) and Aura (01/2003 launch) spacecrafts.

Major features of the latest GEOS-DAS include: high spatial resolution, improved physical parameterizations of the general circulation model (GCM), and an enhanced analysis algorithm called the Physical-space Statistical Analysis System (PSAS). The improvements in the physical parameterizations include a Mosaic land-surface model and a moisture turbulence scheme in the planetary boundary layer. Also, the new GEOS-DAS moisture analysis uses rawinsonde moisture measurements to estimate model bias and to correct the model forecast accordingly. Furthermore, GEOS-DAS incorporates NESDIS and Wentz SSM/I total precipitation water (TPW) into the assimilation. PSAS replaces the optimal interpolation (OI) methodology used in the previous assimilation system (GEOS-1).

The full time series provides 136 physical quantities including wind, temperature, humidity, cloud parameters, total ozone and other important surface parameters. The data have horizontal resolution of 1 degree latitude by 1 degree longitude and 36 vertical pressure levels (except ozone which have a horizontal resolution of 2 degree latitude by 2.5 degree longitude and 42 vertical pressure levels). Time-averaged products are averaged over a 3hour period for single level files or a 6hour period for pressure level files. The data are in HDF-EOS (Hierarchical Data Format – Earth Observing System) format.

The Atmospheric Dynamics Data Support Team (ADDST: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/atmospheric_dynamics/) at the GES DISC/DAAC will provide support for data distribution, documentation, web-based visualization and analysis tools, and read software for the GEOS-Terra DAS data products. The data can be freely obtained via the EOS Data Gateway (EDG), the GES DISC/DAAC Search and Order WWW interface, or an FTP containing subsetted and reformatted data products.

This paper presents an overview of the GEOS-DAS data and the WWW interfaces for data search, online quality analysis, ordering and subscription services