Abstract
The campaign of stratospheric aerosol measurement by balloon-borne optical particle counter was conducted four times from April 1997 to March 1999 at Bandung, Indonesia (6.9°S, 107.6°E). Within a few kilometers above the tropopause low aerosol mixing ratios were observed. The layer of relatively small aerosols (size ranges from 0.15 μm to 0.25 μm and from 0.25 μm to 0.4 μm in radius) resided at high altitudes around or above 30 km, while the layer of relatively large aerosols (size range larger than 0.4 μm in radius) resided around 23 km. Peak mixing ratio of the latter layer decreased year by year, suggesting the layer to be originated from the Pinatubo eruption in 1991. The height of the peak mixing ratio of the relatively small particles was relatively low on October 4, 1998, when the stratosphere above 23 km was in the westerly shear phase of the quasi biennial oscillation.
