Retrieval of Cloud Parameters from Satellite Sounder Data: A Simulation Study

Abstract

Estimates of cloud-top pressure and effective fractional cloud cover may be retrieved from satellite infrared sounder data. This paper presents the results of a simulation study which provides some insights into the relative performance of different retrieval methods and of different combinations of spectral channels. The “minimum residual method,” a variant of a technique described previously by other authors, is presented. It is applied here to groups of HIRS-2 channels and some aspects of its performance for different combinations of channels are examined using simulated data. It is also compared with the “radiance rationing method.” Calculations suggest that the minimum residual method is comparable in performance to the radiance rationing method for high cloud but better for midlevel cloud. The relationship (and relative performance) of these methods to that used operationally to assign pressures to cloud tracers in Meteosat data is also discussed. The methods presented are for retrieving cloud parameters alone and have practical applications as such. However, they may also be used as a means of obtaining first-guess cloud parameters within satellite sounding inversion schemes which retrieve simultaneously atmospheric temperature and humidity profiles along with cloud and surface parameters.