11th Conference on Atmospheric Radiation and the 11th Conference on Cloud Physics

Thursday, 6 June 2002: 9:30 AM
Aerosol Type Classification with SeaWiFS four-channel radiance data
Akiko Higurashi, National Institute for Environmental Studies, Ibaraki, Japan; and Teruyuki Nakajima, Center for Climate System Research, University of Tokyo, Tokyo, Japan
Poster PDF (1.3 MB)
To get the knowledge of the aerosol type is valuable for climate change studies, since aerosol climate effects considerably differ from one type of aerosol to another. Climatologically most important aerosols are soil dust, carbonaceous, sulfate, and sea salt aerosols. These four kinds of aerosols are classified with their particle size and absorptivity of radiation.

In this study, we have developed a four-channel algorithm to retrieve the aerosol optical thickness, Agstrom exponent, and absorptivity of radiation in blue spectral region, and aerosols has been classified into four major aerosol types using the retrieved parameters. The algorithm has been applied to the SeaWiFS data in a joint field experiment of APEX (Asian Atmospheric Particle Environmental Change Studies) and ACE-Asia (Asian Pacific Region Aerosol Characterization Experiment), which took place during the spring of 2001.

The algorithm has classified aerosols in intensive Asian dust storm cases into the soil dust category successfully, and this distribution was in good agreement with the absorbing aerosol distribution shown by TOMS aerosol index. On the other hand, there were cases that TOMS could not detect an aerosol signal off the east China, whereas the present algorithm classified the aerosols as carbonaceous. Taking into account that a chemical transport model expected the airmass with mixed sulfate and carbonaceous aerosols, it is found that the present algorithm tends to classify the mixed airmass as carbonaceous. Because the radiances in blue channels are affected more by absorbing carbonaceous aerosols than by sulfate aerosols. We like to show large scale distributions of four type aerosols and also some validation comparison with ground-based measurements.

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