SIZE DISTRIBUTION OF AEROSOL PARTICLES OVER THE WESTERN PACIFIC OCEAN AND THE SOUTHERN OCEAN

On cruise KH-94-4 of the research vessel HAKUHO MARU, we measured aerosol concentrations over the western Pacific Ocean and the Southern Ocean. Aitken particle concentration was measured with a Pollak condensation nuclei counter. Size distribution for large and giant particles was measured with an optical particle counter. On this expedition, we observed at a nearly fixed station (64-65.5°S, 140°E) twice, in December 1994 and January 1995,for a total of sixteen days. The concentrations of Aitken particles at the fixed station were somewhat higher than those measured around 10°N latitude during this expedition and previous expeditions. These values were nearly equal to or lower than values obtained by other workers. Moreover, Aitken particle concentration at the fixed station sometimes showed a clear diurnal variation. This implies that they were produced by gas-to-particle conversion of organosulfur gases. For large and giant particles, we first confirmed the effect of wind force on the size distribution over the Southern Ocean. These results suggest that the principal constituents of particles over the Southern Ocean in summer are sulfur-dominant Aitken particles and sea salt larger particles.