Statistical analysis of observations of polar stratospheric clouds with a lidar in Kiruna, northern Sweden

Abstract

In the present paper, we analyse 11 years of lidar measurements to derive general characteristics of polar stratospheric clouds (PSCs) and to examine how mountain lee waves influence PSC properties. Measurements of PSCs were made with a backscatter lidar located in Kiruna, northern Sweden, in the lee of the Scandinavian mountain range. The statistical analysis demonstrates that nearly half of all observed PSCs consisted of nitric acid trihydrate (NAT) particles, while ice clouds accounted for only a small fraction, and the remainder consisted of supercooled ternary solution (STS) and mixtures of different compositions. Most PSCs were observed around 22 km altitude. Mountain lee waves provide a distinct influence on PSC chemical composition and cloud height distribution. Ice PSCs were about 5 times as frequent, and NAT clouds were about half as frequent under wave conditions. PSCs were on average at 2 km higher altitudes when under the influence of mountain lee waves.