Estimation of optical parameters of yellow sand dust clouds over desert areas from satellite level data

摘要

The yellow sand dust (called "Kosa" in Japanese) transported from the deserts in the northern part of China often covers over East Asia in the late winter and spring. The dust particles in the atmosphere are regarded as a main source of atmospheric aerosols in East Asia. In this study, a new algorithm for estimating the optical properties of yellow sand dusts in the atmosphere and ground reflectances from ADEOS/POLDER data is described. First, the long-range transport of yellow sand dust was simulated to estimate the transport paths and the global mass distribution of yellow sand dust, because it is difficult to identify the widely spread hazy Kosa cloud from POLDER data. Next, the optical properties of hazy Kosa clouds over the desert area and ground reflectances were estimated, using the multi-viewing reflectances and polarizations at wavelengths 443nm and 670nm in several points selected from the POLDER image. As a result, it is shown that the refractive index of yellow sand dust is in the range from 1.45 to 1.55, and the optical thickness of yellow sand dust, t(443nm) is 0.42 to 0.47, ground reflectance of the desert is 0.09 to 0.15 at the 443nm channel, 0.28 to 0.31 at the 670nm channel.