Some optical properties of smoke aerosol in Indonesia and tropical Australia

Aerosol light-scattering coefficient at 530 nm and its hygroscopic growth w ere determined in biomass-burning smoke in the lower atmosphere over Kalima ntan and northern Australia during the 1997 dry-season fires. Both in and a way from plumes, light-scattering was considerably greater in the Indonesia n region and hygroscopic growth in scattering was also consistently greater . The relative increase in scattering, from 20% to 80% relative humidity, w as typically 1.37 in northern Australian and 1.65 in Kalimantan. Limited ae rosol light absorption data indicate relatively small absorption in the Ind onesian smoke. In part these differences can be explained by different comb ustion phases, mixed naming and smoldering in the Australian savanna fires compared with predominantly smoldering in Indonesia, although these and oth er concurrent measurements suggest that underground peat combustion may hav e made a significant contribution to the Indonesian smoke.