Seminars

Lecturer: Farahnaz Khosrawi, MISU
Date: 2008-10-07 13:30
Place: Aniara

Lidar observations and simulations of polar stratospheric clouds during the Arctic winter 1997 and 2005

Polar stratospheric clouds (PSC) play a key role in stratospheric ozone depletion since heterogenous chemical reactions on the surfaces of the cloud particles activate halogen compounds which initiate the chemical reactions which lead to the observed destruction of ozone in the polar regions during winter. Lidar measurements are well suited to observe and classify PSCs. On 16 January 1997 and 5 January 2005 simultaneous measurements were performed at the east and west side of the Scandinavian mountains by the U Bonn lidar located at Esrange and the RMR lidar in Alomar. On both dates PSCs were observed at both stations. On 16 January 2007 the PSC occurred between 22-26 km and was mainly composed of STS (supercooled ternary solution) and of ice at 25 km. On 5 January 2005 the PSC occurred at altitudes between 19-23 km and was composed mainly of STS during the entire measurement. At the upper edge of the PSC solid particles existed which led to a classification of mixed layers (containing STS and nitric acid trihydrate (NAT) particles). A microphysical box model has been used to simulate the formation of the STS particles. The box model simulation show that the STS PSC was formed in 1997 about 10 hours prior to the observation and in 2005 about 20 hours prior to the observation. The formation of the PSC in 1997 was partly induced synoptically and partly by waves while the formation of the PSC in 2005 was only induced synoptically.

Created 2008-09-26 18:25:43 by Uwe Raffalski
Last changed 2008-10-06 21:24:57 by Uwe Raffalski