Abstract
Aircraft observation of aerosol particles was carried out at an altitude of approximately 4.5 km from 0°-34°N during 7-10 March 1989. Marked spatial variation in the number concentrations of aerosol particles with radii between 0. 15 and 5 μm was observed in the middle troposphere, with concentrations ranging from 0. 1 to 10cm-3. Sulfate-containing particles (both H2SO4 and (NH4)2SO4) were present in the observation regions as an important background aerosol. However, high concentrations of particles were observed intermittently in the tropical atmosphere in association with the vertical transport of sea-salt particles through convective clouds. Asian dust-storm particles also contributed to high concentrations of particles with radii r &ge ; 1 μm at mid-latitudes. The present study suggests that the transport of sea-salt particles and mineral particles contribute strongly to increases in the number concentration of aerosol particles in the middle troposphere. Modification of sea-salt particles collected over the tropical region is also discussed in this paper.
