The GEOS ozone data assimilation system Original Research Article

A data assimilation system for ozone observations has been developed at NASAʹs Goddard Space Flight Center. The initial objective is to provide total ozone and ozone profiles in near-real time for satellite remote sensing applications. In addition, historical ozone observations will be assimilated for climate and chemistry studies. The forecast model is a chemistry and transport model with prescribed, zonally symmetric ozone production and loss rates. The analysis equation is solved after each model time step, using observations obtained within a time window with a length of one time step. In this article, the overall design of the system is described, and examples from the validation of the initial configuration assimilating TOMS total ozone and SBUV/2 ozone profile measurements are presented. The assimilation produces realistic total ozone fields and lower stratospheric ozone profiles. A substantial bias with respect to observed profiles remains in the upper stratosphere.