Polar Stratospheric Clouds

Polar Stratospheric Clouds (PSC), which are very frequent above Antarctica and the Arctic during wintertime, contribute to the formation of the ozone hole and slow down its recovery. These clouds differ greatly from traditional tropospheric clouds, as they are created through various combinations of stratospheric water vapour, HNO3 and H2SO4 (leading to the formation of ice, NAT and STS particles); PSC composition will determine its impact on ozone loss. However, due to their hard-to-reach location, and their difficult detection using passive remote sensing instruments, we still have a lot to learn about how various atmospheric processes (such as orographic gravity waves) and microphysical processes (such as heterogeneous nucleation) drive their formation and composition. Here we take advantage of the high resolution offered by the CALIOP lidar, its sensitivity to optically thin atmospheric features and its ability to retrieve the shape of airborne particles to document across several years the spatial cover and the composition of PSC, and the evolution of both throughout polar winters. Using the synergy between instruments and the large coverage of polar regions offered by the A-Train constellation, complemented by ground-based observations and atmospheric modelling, we will relate these found properties with local and large-scale atmospheric phenomenons, to identify and describe the processes that drive their formation and composition.

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