Time Series Algorithm for Aerosol Retrievals from Modis

The Earth Observing System [1] initiated high quality global Earth observations and operational aerosol retrievals over land. With the wide swath (2300 km) of MODIS instrument, the MODIS Dark Target algorithm [2-3] currently complemented with the Deep Blue method [4] provides daily global view of planetary atmospheric aerosol. With MODIS aerosol program being very successful, there are still several unresolved issues in the retrieval algorithms. The current processing is pixel-based and relies on a single-orbit data. Such an approach produces a single measurement for every pixel characterized by two main unknowns, aerosol optical thickness (AOT) and surface reflectance. For this reason, MODIS Dark Target algorithm makes spectral assumptions about surface reflectance, whereas the Deep Blue method uses ancillary global database of surface reflectance. Both algorithms assume Lambertian surface in the radiative transfer model.