A synopsis of CALIPSO Polar Stratospheric Cloud Observations from 2006-2014

Abstract

Polar stratospheric clouds (PSCs) are known to play key roles in the springtime chemical depletion of ozone at high latitudes. PSC particles provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation, which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs. CALIOP began data collection in mid-June 2006 and has since acquired, on average, over 300,000 backscatter profiles daily at latitudes between 55° and 82° in both hemispheres. PSCs are detected in the CALIOP backscatter profiles as enhancements above the background aerosol in either 532-nm scattering ratio (the ratio of total-to-molecular backscatter) or 532-nm perpendicular-polarized backscatter. CALIOP PSCs are separated into composition classes based on the ensemble 532- nm scattering ratio and 532-nm particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT and ice particles). In this paper, we provide an overview of the CALIOP PSC measurements and then examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on vortex-wide scales for entire PSC seasons over the more than eight-year data record.