Retrieval of Integrated Water Vapour and Cloud Liquid Water Contents

Abstract

Since the mid seventies, spaceborne microwave radiometers have been used to get information about the atmosphere above oceans. Retrieval of water vapour content was performed first with the ESMR (Electrically Scanning Microwave Radiometer) flown on the Nimbus-5 satellite, then operational products from the SMMR (Scanning Multichannel Microwave Radiometer) onboard SEASAT and Nimbus-7 were routinely delivered (Wilheit and Chang, 1980, Prabhakara et al, 1983). The bases for establishing the retrieval of water vapour and cloud liquid water contents were thus established at the end of the seventies and beginning of the eighties, and most of the improvements achieved to date concern the tools used to perform the retrieval and the performances of the sensor. The SSMI (Special Sensor Microwave Imager) series has been flown continuously since 1987 to provide several products over oceans. Thanks to the good stability and calibration of its seven channels (between 19 and 85 GHz), many studies were performed to improve and evaluate the quality of the retrieval methods for atmosphere and ocean surface. Other microwave radiometers have been used to retrieve water vapour and liquid water contents, both on satellite and on ground, the latter helping to assess the spaceborne retrievals, as well as to analyse in details atmospheric transmittance modelling at microwave frequencies. Research are now developing on the retrieval of the water vapour profile, by using sensors with high frequencies as SSMT-2 and AMSU