TECHNIQUES FOR THE RETRIEVAL OF AEROSOL PROPERTIES OVER LAND AND OCEAN USING MULTIANGLE IMAGING

Aerosols are believed to play a direct role in the radiation budget of earth, but their net radiative effect is not well established, partic ularly on regional scales, Whether aerosols heat or cool a given locat ion depends on their composition and column amount and on the surface albedo, information that is not routinely available, especially over l and. Obtaining global information on aerosol and surface radiative cha racteristics, over both ocean and land, is a task of the Multi-angle I maging SpectroRadiometer (MISR), an instrument to be launched in 1998 on the Earth Observing System (EOS)-AM1 platform. Three algorithms are described that will be implemented to retrieve aerosol properties glo bally using MISR data. Because of the large volume of data to be proce ssed on a daily basis, these algorithms rely on lookup tables of atmos pheric radiative parameters and predetermined aerosol mixture models t o expedite the radiative transfer (RT) calculations. Over oceans, the ''dark water'' algorithm is used, taking full advantage of the nature of the MISR data. Over land, a choice of algorithms is made, depending on the surface types within a scene-dark water bodies, heavily vegeta ted areas, or high-contrast terrain. The retrieval algorithms are test ed on simulated MISR data, computed using realistic aerosol and surfac e reflectance models. The results indicate that aerosol optical depth can be retrieved with an accuracy of 0.05 or 10%, whichever is greater , and some information can be obtained about the aerosol chemical and physical properties.