Retrieval of Non-spherical Dust Aerosol from PARASOL

Knowledge about dust aerosols is essential for global climate change and radiation budget studies. To correctly retrieve the dust aerosol optical properties, one needs to consider the effect of non-sphericity. As an initial step to take into account of the non-sphericity, a spheroid model along with an aspect ratio is introduced. Due to the high sensitivity of multi-angle polarimetric measurements to the microphysical properties of dust aerosols, he PARASOL level 1 product is used in this research. The three components I, Q, U of the Stokes vector in up to 15 directions for one pixel are used in the retrieval process. Instead of using the LUT technique, an iterative search method, the Levenberg-Marquardt method, is employed to solve the inverse problem, where the aerosol aspect ratio, the particle size distribution, the optical depth and the land surface properties are simultaneously retrieved. One day of POLDER data over the Sahara is used to test this algorithm. To fully make use of the multi-spectral measurements, the spectral independent variables retrieved by the 670P channel are compared with the 490P results. Furthermore, comparisons with the MODIS deep blue aerosol product have also been made.