EXTRACTION OF AEROSOL PROPERTIES AND SURFACE REFLECTANCE FROM POLDER DATA OVER LAND

It is as yet very difficult to extract optical properties of atmospheric aerosols from satellite data over land. The PARASOL/POLDER observes the reflectance and polarization of a target quasi-simultaneously in multi-viewing angles at wavelengths of 490nm, 670nm and 865nm. In this study, a new estimation method of aerosol properties using the polarized radiance effectively is described. The polarized radiance at the top of the atmosphere does not depend on the surface reflectance if the ground surface is assumed to be the uniform Lambertian reflector. First of all, the optical thickness tau, the refractive index Nr and the size distribution a (index of Junge power-law) of aerosols is estimated from polarized radiances at 670nm received by the POLDER. In this case, it was assumed that the imaginary part of complex refractive index, Ni, is zero because there is very little absorption for dust particles at 670nm. After that, the surface reflectance A is obtained from total radiances at 670nm. Next, the tau, Ni (the imaginary part of complex refractive index) at 490nm are estimated from polarized radiances because the absorption of light ray by aerosols is not ignored. The surface reflectance A at 490nm is estimated at the same way as the case of 670nm. Finally, the method described here was applied to PARASOL/POLDER data over land taken on April 28, 2006. As a result, it is shown that this algorithm provides reasonable values for aerosol properties and surface reflectance.