SUBMICRON AEROSOL SIZE DISTRIBUTIONS MEASURED OVER THE TROPICAL AND SOUTH-PACIFIC

Size distributions of aerosol particles in the radius range of 0.006-0.53 μm were measured over the Pacific Ocean along the 150° longitude from about 20°N to 55°S. Throughout the tropical trade wind region, the size distribution of fine particles was relatively stable and exhibited a double-peaked characteristic with one peak at about 0.1 μm and the other in the 0.02-0.04 μm region, separated by a minimum at about 0.06 μm. The total concentrations of particles were in the 150-300 cm-3 range with 60-150 cm-3 residing in the accumulation mode (0.06<r<0.5 μm). South of the trade wind region, the measured size distributions and meteorological conditions were more diverse. Periods with very low concentrations in the accumulation mode were associated with regions of large-scale precipitation. Large increases in the number of nucleation mode particles were found in air masses with low concentrations of particles in the accumulation mode. © 1990.