Polarization Properties of Middle and High Level Clouds Observed by Lidar

[摘要] Observations of the fine structure of clouds have been made with a ruby lidar at the Meteorological Research Institute (36.1°N, 140.1°E), Tsukuba, Japan. Case studies of depolarization ratios of middle and high level clouds are presented. The middle level clouds observed on 16 October 1984 and 10 May 1985 had high values of the depolarization ratio at the cloud base and low values at the center of the cloud layer where the backscattered signals of the parallel component were large. For cirrus clouds observed on 24 and 27 February 1987, depolarization ratios were greater than 10 percents through the cloud layers where the atmospheric temperature was below -40°C. On the other hand, cirrus clouds observed on 11 June 1987 showed variable vertical profiles of the depolarization ratios in the cloud layers where atmospheric temperatures were -20°C to -40°C. While there were regions of depolarization ratio of a few percents in the cloud layer, the layers with depolarization ratio greater than 10 percents lowered toward the cloud base with time. The rate of descent varied from about 0.74 to 1.28m/s. Depolarization ratios in high level clouds showed a tendency to increase when the atmospheric temperature decreased.

[学科分类] 大气科学