A data assimilation system has been developed at the UK Meteorological Office to analyze the mix of observations available in the troposphere and stratosphere. The data assimilation system is based on the analysis correction scheme used at the UK Meteorological Office for operational weather forecasting.

The assimilation system is currently being used to supply near real-time analyses of meteorological fields from the troposphere and stratosphere to the Upper Atmosphere Research Satellite (UARS) Science Team. At this stage, these analyses are based on a similar set of observations to the operational analyses, so they provide an independent check of the UARS observations. In the stratosphere they are largely based on soundings from the National Oceanic and Atmospheric Administration polar orbiters.

Some results from the assimilation 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 described. First, the vertical domain of the model will be extended into the middle mesosphere, with some improvement in vertical resolution. Second, the system will he extended to assimilate data from UARS instruments in addition to the other observation types; these UARS data will include observations of temperatures, winds, and long-lived chemical species.

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