Estimation of Optical Properties of Asian Dust over the Land Surface by Polarization Measurements

It is very difficult to extract optical properties of the widely spread hazy dust from satellite data over the land surface because the radiance received by a satellite sensor strongly depends on the surface reflectance. In this study, optical properties of the Asian dust, such as the optical thickness (t), the complex refractive index (Nr + iNi), the number size distribution of dust particles (index of Junge power-law, a) and the target reflectance (A), are estimated from PODER data and ground-based polarization measurement data. First of all, the values of t, Nr, a and A are estimated at the 670 nm channel. Then, using the value of a (size distribution) and Nr obtained at 670 nm, the values of t, A and Ni at 443 nm are estimated from grand-based polarization measurement data. This method is applied to POLDER data taken on May 3, 2003 and ground-based polarization data measured at the almost same time as the overpass of the satellite.