Aerosol analysis with the Coastal Zone Color Scanner (CZCS): the Australasian region

Abstract

The Channel 4 data from the Coastal Zone Color Scanner (CZCS), a space-borne radiometer, was analyzed to infer aerosol distributions in the Australasian region for 1979. Monthly, seasonal, and annual composites of the Channel 4 data were created. An accompanying data density image was created for each composite to indicate the degree of data coverage. Australian climatological data and 1000mb and 850mb monthly mean wind fields were used to interpret the dominant features in the composites. Because the primary source of the measured radiances in the Channel 4 data was thought to be suspended dust, it was theorized that the dominant aerosol features would be located downwind of regions with high dust storm activity. Elevated 670nm radiances were observed throughout 1979 within the portion of study region located between-I 5'S and the equator. However, the wind field data and rainfall climatology did not support dust transport to this region. Although biomass burning and biogenic hydrocarbon production were likely aerosol sources, the Channel 4 data suggested that they were not likely to be the primary source for the elevated radiances in the region. The low level wind fields and climatological data supported the feasibility of dust transport off the northwest coast of Australia over the Indian Ocean. The 1979 CZCS data indicated elevated 670nm radiances did occur in this region. However, the pattern of the signal suggested these radiances may not have been due to dust transport. The daily 670nm images indicated sun glint and faulty cloud-masking were probable sources for the observed radiances. The fallout of dust over New Zealand and mineral-rich deposits in sea floor sediments support the established theory of aeolian dust transport over the Tasman Sea. Elevated 670nm radiances were observed during the 1979 summer season, corroborating the existing empirical evidence. The seasonal climatology, dust storm activity, and wind field data further supported the theory of aeolian dust transport over the region during the summer months. Furthermore, due to fewer clouds and less sun glint, the potential problems with the CZCS algorithm were also thought to be reduced.