Aerosol detection by TOMS and POLDER over oceanic regions

In this paper we investigate the aerosol content retrieved by Earth-Probe Total Ozone Mapping Spectrometer (TOMS) and ADEOS POLDER over oceanic regions for the period November 1996 to June 1997. We combine the aerosol index (AI) derived from TOMS corresponding to UV-absorbing aerosols (desert dust and biomass-burning particles) and the POLDER aerosol optical thickness (AOT) and Angstrom coefficients. The seasonal composited images from the two sensors show in general consistent spatial distributions of the aerosol over oceans, with the highest aerosol content retrieved over the north tropical and equatorial Atlantic. Over the different oceanic regions investigated (i.e., Atlantic Ocean, Mediterranean Sea, Indian Ocean, and Pacific Ocean), TOMS and POLDER show a good correspondence in the aerosol seasonal variability. At all sites with the exception of the region of the Sea of Japan, we show that during the time periods of maximum aerosol amounts, a linear correlation exists between the TOMS AI and POLDER AOT. For the Sea of Japan the influence of different aerosol types (i.e., desert dust and sulfates) is likely to complicate the TOMS detection. For the other oceanic regions, our results suggest a large variability in the relationship between the TOMS Al and the POLDER AOT, which is likely to be related to changes in aerosol composition and/or altitude.