Lidar observations of the horizontal orientation of ice crystals in cirrus clouds

Abstract

A scanning lidar system has been used at Aberystwyth (52.4°N, 4.1°W) to measure the backscatter and depolarization ratios in cirrus clouds. The measurements indicate that the height of maximum occurrence was near 9 km and that about 50% of clouds showed the presence at some height of ice crystals having a near horizontal orientation. The angular dependence of the backscatter about the vertical showed that the maximum tilt angle of these crystals from the horizontal plane was about 0.3°.