The Operational Sounding of the Lower Atmosphere from Satellites using Millimetre Waves

This paper discusses the increasing use of millimetre waves for passive sounding of the lowest 15 km of the atmosphere in support of the forecasting activities of the Meteorological Office. The paper starts with a brief discussion of the spectral features in the 23 to 200 GHz region and how meteorologically useful measurements can be derived. This defines the performance specification of satellite microwave radiometers. A discussion of the evolution of such radiometers leads to the development of the Advanced Microwave Sounding Unit (polar orbiter) and the proposal for a microwave sounder on second generation METEOSAT. The paper also briefly discusses the supporting scientific programmes and calibration aspects.