A STRATOSPHERE TROPOSPHERE DATA ASSIMILATION SYSTEM

A data assimilation system has been developed at the UK Meteorological Office to analyze the mix of observations available in the tropospher e and stratosphere. The data assimilation system is based on the analy sis correction scheme used at the UK Meteorological Office for operati onal weather forecasting. The assimilation system is currently being u sed to supply near real-time analyses of meteorological fields from th e troposphere and stratosphere to the Upper Atmosphere Research Satell ite (UARS) Science Team. At this stage, these analyses are based on a similar set of observations to the operational analyses, so they provi de an independent check of the UARS observations. In the stratosphere they are largely based on soundings from the National Oceanic and Atmo spheric Administration polar orbiters. Some results from the assimilat ion system are presented for periods in January and August 1992. They are compared with equivalent products from the National Meteorological Center. A particular study is made of the Arctic polar vortex in late January. Future developments of the assimilation system are also desc ribed. First, the vertical domain of the model will be extended into t he middle mesosphere, with some improvement in vertical resolution. Se cond, the system will be extended to assimilate data from UARS instrum ents in addition to the other observation types; these UARS data will include observations of temperatures, winds, and long-lived chemical s pecies.