printlogo
http://www.ethz.ch/index_EN
Institute for Atmospheric and Climate Science
 
print
  

Cirrus Clouds and Contrails

Thomas Peter, Ulrich Krieger, Beni Zobrist, Claudia Marcolli

Cirrus clouds exist in the upper troposphere, at altitudes between about 7 to 17 km. They can appear as wide sheets, wispy filaments, and also as subvisible cloud layers. Cirrus clouds are composed of non-spherical ice particles with particle sizes and number densities varying considerably with meteorological conditions and origin of the air in which they form. Because cirrus clouds cover up to 30% of the Earth they play an important role in atmospheric chemistry and climate. Cirrus clouds have a net heating effect on the Earth. This is because they only hardly affect the amount of incoming visible light from the sun, but efficiently absorb the outgoing infrared radiation from the Earth's surface, part of which they reemit back to the surface. Since cirrus clouds are very efficient in heating the surface, even small changes in cirrus cloud coverage may significantly alter the Earth's climate. Observations indicate that the mean global cirrus cloud occurrence frequency over the oceans has increased by several percent per decade. This increase in cirrus may be related to human activities such as air traffic. However, since the exact mechanisms of formation for cirrus clouds are still unknown it is difficult to predict how anthropogenic activities will change cloud abundances in the future.

 

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

© 2014 ETH Zurich | Imprint | Disclaimer | 4 September 2008
top