REMOTE SOUNDING OF CIRRUS CLOUD OPTICAL DEPTHS AND ICE CRYSTAL SIZES FROM AVHRR DATA - VERIFICATION USING FIRE-II IFO MEASUREMENTS

Using the data obtained from the Advanced Very High Resolution Radiome ter (AVHRR) 3.7-mu m and 10.9-mu m channels, a retrieval scheme has be en developed to simultaneously infer cirrus cloud optical depth and me an effective ice crystal size based on the theory of radiative transfe r and parameterizations. A numerical scheme is further developed to re move the solar component in the 3.7-mu m radiance for applications to daytime satellite data. This scheme is based on the correlation betwee n the 3.7-mu m (solar) and 0.63-mu m reflectances. Validation of the a lgorithm has been performed by using various datasets that were collec ted during the FIRE-II IFO (Nov-Dec 1991) at Coffeyville, Kansas. We h ave focused on the 26 November and 5 December cases. The retrieval ana lysis over a 0.5 degrees x 1.0 degrees area is performed around Coffey ville for each case based on AVHRR-HRPT data. For validation the autho rs analyze the photomicrograph data collected by the balloonborne repl icator, determine the microphysical and optical properties of the samp led cirrus clouds, and derive their position at the satellite overpass based on sounding data. It is demonstrated that the retrieved cirrus cloud temperature, mean effective ice crystal size, and optical depth closely match the observed values. Further, the retrieved cirrus cloud properties are applied to the computation of surface radiative fluxes using a radiative transfer program that involves a consistent represe ntation of cirrus cloud fields. The computed values are compared with the data measured from ground-based radiometers, and it is shown that the computed downward surface IR and solar fluxes are within 5 and 10 W m(-2) of the measured values, respectively, near the time of satelli te overpass.