printlogo
ETH Zuerich - Homepage
Institute for Atmospheric and Climate Science
 
Search
ETH Zurich - D-UWIS - IACETH - Research - Atmospheric Chemistry and Aerosol Physics - Polar Stratospheric Clouds 
print
  

Polar Stratospheric Clouds

Newsworthy

New coordinates from 1 Sep 2005 on!

The Master programme in Atmospheric and Climate Science will start in October 2006! You can apply for it via e-apply from 1 April 2006 onwards!

Observations of polar stratospheric clouds (PSCs) date back to the end of the 19th century. These opalescent clouds exist in the lower stratosphere, at altitudes between about 15 to 25 km. They are only found in the polar regions where stratospheric temperatures fall below about 200 K, cold enough to initiate their formation. Some PSCs are known to be liquid particles composed of supercooled ternary solutions of sulfuric acid, nitric acid, and water. Others are composed of nitric acid trihydrate which is the thermodynamically stable form of HNO3 and H2O in the polar stratosphere. Long thought to be essentially irrelevant for atmospheric chemistry it is now accepted that PSCs are an important ingredient in polar ozone destruction and the formation of the ozone hole. PSCs act as catalysts converting chlorine from the inert "reservoir" species ClONO2 and HCl to active species by heterogeneous chemical reactions. In addition, the polar stratosphere can be "denitrified" when HNO3 is permanently removed through sedimentation of large PSC particles. Denitrification removes gaseous nitric acid that could otherwise interrupt the catalytic ozone loss cycle by reforming the reservoir species ClONO2. Unfortunately, both denitrification and ozone loss predictions are uncertain because the composition and formation mechanisms of the particles responsible for denitrification and chlorine activation have still not been established.

Contact: Thomas Peter, Ulrich Krieger, Thomas Koop, Beiping Luo, Christina Colberg, Uwe Weers

top
 

Wichtiger Hinweis:
Diese Website wird in älteren Versionen von Netscape ohne graphische Elemente dargestellt. Die Funktionalität der Website ist aber trotzdem gewährleistet. Wenn Sie diese Website regelmässig benutzen, empfehlen wir Ihnen, auf Ihrem Computer einen aktuellen Browser zu installieren. Weitere Informationen finden Sie auf
folgender Seite.

Important Note:
The content in this site is accessible to any browser or Internet device, however, some graphics will display correctly only in the newer versions of Netscape. To get the most out of our site we suggest you upgrade to a newer browser.
More information

© 2006 ETH Zurich | Imprint | n/a