Polar Stratospheric Clouds over 1 Antarctica from the CALIPSO

1 2 This paper presents statistics of Polar Stratospheric Clouds (PSCs) above Antarctica from 3 June to October 2006 using observations from the CALIOP spaceborne lidar, part of the 4 CALIPSO mission. Synoptic-scale changes in their geographic and temporal distribution 5 are documented on a weekly basis and correlated with temperature fields. A very high 6 spatial and temporal variability tends to contradict the hypothesis that PSCs are mostly 7 created via slow processes mainly governed by large-scale temperature changes. Linear 8 depolarization ratios reveal strongly typed PSCs with distinct characteristics (implying dif-9 ferent microphysics), but most of the time a unique cloud composition cannot be singled 10 out. A West/East imbalance is observed in the depolarization distribution, symptomatic of 11 microphysical disparities. A classification based on depolarization and scattering ratios 12 suggests more than 60% of mixed PSCs, followed by more than 20% of STS, and a 13 roughly equal concentration of NAT-based and pure ice PSCs (~8%). Up to the beginning 14 of August, STS PSCs experience a steady decrease in concentration correlated with an 15 increase in ice-based PSCs ; this tendency gets reversed after the first week of August.