Reanalysis of historical observations and its role in the development of the goddard EOS climate Data Assimilation System

Abstract

The Data Assimilation Office at NASA's Goddard Space Flight Center is currently producing a global multi-year reanalysis of historical observations for the period 1980–1994. The assimilation employs a fixed analysis system (version 1 of the Goddard Earth Observing System or GEOS-1). This eliminates artificial climate signals resulting from system modifications typically found in operational analyses. The GEOS-1 reanalysis has proven to be an important research tool for studying a number of Earth Science problems on time scales ranging from diurnal to interannual. The long record of the reanalysis also allows a more direct study of the role of the observations in the assimilation process. In particular, we examine here the degree to which the observed boundary conditions force the climate variations of the assimilation. We also discuss the near term development of the GEOS system and how the process of data assimilation naturally lends itself to assessing model deficiencies.