Polar stratospheric clouds at the South Pole from 5 years of continuous lidar data: Macrophysical, optical, and thermodynamic properties

An eye-safe micropulse lidar (MPL; 0.523 mm) has operated at the Scott-Amundsen South Pole Station, Antarctica, since December 1999 to collect continuous long-term measurements of polar clouds. A 5-year data subset is presented here to describe macrophysical, optical, and thermodynamic properties of polar stratospheric clouds (PSC) in austral winters 2000 and 2003-2006. PSC cloud occurrence is examined relative to seasonal temperature and theoretical chemical structure. A linear relationship is established with high correlation between total integrated PSC scattering and ozone loss for 2000 and 2003-2005 when springtime overturning of the air mass occurred nominally. In 2006, ozone-depleted air persisted over the South Pole through the end of December. In this case, overturning of the air mass was limited temporally by vortex-related mechanisms, and any correlation with PSC occurrence was eliminated. PSC formed near and above 18.0 km above mean sea level (MSL) in late May and early June likely influence clouds formed at lower heights later in the season from sedimentation, evaporation/sublimation, and repartitioning of nitrogen and water vapor in the air mass bounded by the dynamic polar vortex. Conceptual profiles for seasonal PSC occurrence and thermal structure are described. PSC are common to near and above 20.0 km MSL through June. After this, they are most frequent near 15.0 km MSL through August.