Recent advances in satellite sounding at the UK Meteorological Office

Several improvements have been made at the UK Meteorological Office to the system for deriving temperature and water vapour soundings from global satellite sounding data and for assimilating them into a numerical weather prediction model. The most significant changes include the assimilation of retrieved water profiles and the introduction of a new scheme for extending the model temperature profile to the upper stratosphere. The latter involves the use of stratospheric sounding channels to infer upper level temperatures and is capable of producing realistic retrievals even when the stratospheric circulation is disturbed and the model analyses poor. This is illustrated by the stratospheric warming in January 1995. Care is required to ensure that the extrapolation scheme does not allow any positive feedback within the overall retrieval system. New developments in satellite instrumentation and data processing promise further benefits from satellite sounding data in the near future and ensure that the data will continue to play an important role in numerical weather prediction