Retrieval of Water Vapor Profiles Using SSM/T-2 and SSM/I Data

Abstract

A physically based retrieval algorithm is presented that retrieves water vapor profiles from Special Sensor Microwave/Temperature-2 (SSM/T-2) passive microwave brightness temperature measurements. This method can use SSM/T-2 data alone or in conjunction with data from the Special Sensor Microwave/Imager (SSM/I). Several SSM/I channels, as well as total integrated water vapor (TIWV) retrieved from SSM/I, are tested to see if they add value to the retrieval. In the retrieval process, TIWV is formally treated as a separate channel. It is found that using the SSM/I TIWV increases the yield of the retrieval (the percentage of retrieved profiles whose brightness temperatures agree with the observations, on average, to within the noise level of the instrument), as well as reduces the average normalized brightness temperature error. Also, use of the TIWV allows the omission of the SSM/T-2 150-GHz channel data without a significant impact on results. It is shown that by using the SSM/I TIWV, retrievals can be made further into areas of precipitation and heavy clouds than when using data from only the SSM/T-2. Examples of retrieved profiles are shown to agree with the general features of profiles from radiosondes and the European Centre for Medium-Range Weather Forecasts analyses.