Airborne lidar observations in the wintertime Arctic stratosphere: Polar stratospheric clouds

Abstract

Polar stratospheric cloud (PSC) distributions in the wintertime Arctic stratosphere and their optical characteristics were measured with a multi‐wavelength airborne lidar system as part of the 1989 Airborne Arctic Stratospheric Expedition. PSCs were observed on 10 flights between January 6 and February 2, 1989, into the polar vortex. The PSCs were found in the 14–27 km altitude range in regions where the temperatures were ≤195 K. Two types of aerosols with different optical characteristics (Types Ia and Ib) were observed in PSCs thought to be composed of nitric acid trihydrate. Type Ia PSCs typically exhibited low scattering ratios (1.2–1.5) and high aerosol depolarizations (30–50%) at 603 run, while Type Ib PSCs had higher scattering ratios (3–8) and lower aerosol depolarizations (0.5–2.5%). Water ice PSCs (Type 2) were observed to have high scattering ratios (>10) and high aerosol depolarizations (>10%) at temperatures ≤190 K.