Assessment of the nonsphericity of mineral dust from geostationary satellite measurements

Optical thickness of Asian dust aerosols over the Yellow Sea and the Sea of Japan were retrieved from the visible data of the Geostationary Meteorological Satellite (GMS-5) observed on April 7 and 8, 2000, through look-up tables generated by the doubling and adding method. The retrieved optical thickness, by using conventional spherical particle models, showed unnatural decrease in the middle of day time. The decrease disappeared by the use of the semiempirical theory for nonspherical particles by Pollack and Cuzzi [J. Atmos. Sci. 37 (1980) 868.]. These results are explained by the difference of the phase functions between spherical and nonspherical particles and also the variation of the scattering angle for the target dust area during the satellite measurements. Our results confirm that the use of nonspherical particle model improves the retrieval of dust optical thickness from space.