Large Depolarization Ratio of the Winter Antarctic Stratospheric Aerosol Layer: Lidar Measurement at Syowa Station (69°00'S, 39°35'E), Antarctica

摘要

The lidar measurement on stratospheric aerosols made at Syowa Station (69°00'S, 39°35'E), Antarctica in 1983 is described. In early winter, stratospheric aerosol content began to increase rapidly corresponding with temperature decrease. During this period, depolarization ratio of aerosol layer was low. After then, not only aerosol content but also depolarization ratio were in high level in winter 1983. These suggest that nonspherical particles were actively formed in the cold winter stratosphere, and confirm that the suggestion by Steele et al. (1983), in which increase of particulate matter in the winter polar stratosphere is assumed to be due to the growth of individual ice crystals through sublimation of water vapor molecules, is important factor controlling the winter enhancement of polar stratospheric aerosols. However, the measurement in the early winter showed that the increase in particulate matter in the winter stratosphere is not only due to the growth of individual nonspherical particles but due to some other processes. Additionally balloon measurement made on June 3rd showed that there were lots of large particles (about 15 particles cm-3) in the lower stratosphere. The growth of Aitken particle to large particle is speculated as another possible process causing the increase in particulate matter content in the winter polar stratosphere.