The Use of Visible Data in VAS Temperature Soundings

Abstract

A method is developed that makes use of visible reflectance data to provide cloud information from the retrieval of atmospheric vertical soundings from VAS geostationary radiance observations. The technique enables estimates of fractional cloud amount for each 8?16 km VAS infrared field of view. Cloud top pressure is calculated using the CO2 slicing method or, for low-level opaque overcast cloud conditions, estimated from the VAS-observed, 11-?,a window channel, effective brightness temperature, and the temperature profile. For semi-transparent cloud, the emissivity is obtained from the cloud level atmospheric temperature, which corresponds to the cloud top pressure derived from the CO2 slicing method, and VAS 11-? window channel, effective brightness temperature. With the effective cloud amount and cloud top pressure, the proper clear and cloudy weighting functions of the radiative transfer equation (RTE) are specified, and a direct physical inverse solution of the RTE is used to produce vertical temperature and moisture soundings. Additionally, the surface skin temperature is also estimated as pan of the temperature and water vapor profile retrieval processes. The results obtained from the application of this technique are compared with surface hourly reports, radiosonde observations and vertical profiles from the retrieval method without visible data. The intermmparisons reveal that the use of visible channel data yields significant improvements both in the reliability and the accuracy of satellite derived atmospheric profiles.