Two Different Stages in Polar Stratospheric Clouds Events Lidar Backscatter of Particulate Matter and Temperature in the Antarctic Stratosphere

Abstract

Two different types of aerosols were observed during Polar Stratospheric Clouds (PSCs) events at Syowa Station (69°00'S, 39°35'E) using a lidar. Thermodynamical discussion on particle forms in the Antarctic winter stratosphere suggests that these two types were possibly nitric acid trihydrated (NAT) crystal and ice crystal, and in the early stage of a PSCs event most of the particles are NAT, and in the fully developed stage the major component is ice crystals. Early stage PSCs sometimes contained an ice crystal particle layer in their lower layer, possibly due to water vapor inlet from the troposphere; the ice particles appear without nucleation on NAT particles.
The region where PSCs particles can actively form expanded to near the tropopause in the fully developed stage of PSCs. Particle descent from the stratosphere to the troposphere is certainly active under such conditions, and thereby this motion is an important sink of stratospheric particulate matter and relating gases. Denitrification of the stratosphere due to this will be an important process for disturbing Antarctic ozone.