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1 LMD - Laboratoire de Météorologie Dynamique 2 IPSL - Institut Pierre-Simon-Laplace 3 LaRC - NASA Langley Research Center Hampton

Abstract : This paper presents statistics of polar stratospheric clouds PSCs above Antarctica from June to October 2006 using observations from the Cloud-Aerosol Lidar with Orthogonal Polarization CALIOP spaceborne lidar, part of the CALIPSO mission. Synoptic-scale changes in geographic and temporal distribution are documented weekly and correlated with temperature fields. A high spatial and temporal variability tends to contradict the hypothesis that PSCs are mostly created via slow processes mainly governed by large-scale temperature changes. Linear depolarization ratios reveal strongly typed PSCs with distinct characteristics implying different microphysics, but unique cloud compositions cannot be singled out. A west-east imbalance is observed in the depolarization distribution, symptomatic of microphysical disparities. A classification based on depolarization and scattering ratios suggests more than 60% of mixed PSCs, followed by more than 20% of STS, and a roughly equal concentration of nitric acid trihydrate NAT-based and pure ice PSCs ∼8%. Up to the beginning of August, supercooled ternary solution STS PSCs experience a steady decrease in concentration correlated with an increase in ice-based and mixed PSCs; this tendency gets reversed after the first week of August, hinting at the existence of a large-scale seasonal cycle in PSC population.

Keywords : PSC lidar CALIOP microphysics

Autor: Vincent Noel - Albert Hertzog - Hélène Chepfer - David Winker -

Fuente: https://hal.archives-ouvertes.fr/


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