OPTICAL BACKSCATTER CHARACTERISTICS OF ARCTIC POLAR STRATOSPHERIC CLOUDS

Airborne lidar measurements have been made of polar stratospheric clouds (PSCs) during the Airborne Arctic Stratospheric Expedition in January–February 1989.These show the existence of a systematic relationship between the backscatter depolarization ratio, δ, and the (aerosol + molecular)/molecular backscatter ratio, R.The data are consistent with a two population PSC particle model. The first population consists of particles with low values for δ (≤ 0.02) and low to intermediate values for R (≤ 6). The second population is characterized by higher values for δ (up to 0.60) and R (up to 40 or greater). The relationship between δ and R, observed within a limited range of altitudes and latitudes, corresponds to a mixture of the two populations with variable concentrations but constant optical properties. Copyright 1990 by the American Geophysical Union.