Document Detail

Global circulation as the main source of cloud activity on Titan.
MedLine Citation:
PMID:  19494910     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Clouds on Titan result from the condensation of methane and ethane and, as on other planets, are primarily structured by circulation of the atmosphere. At present, cloud activity mainly occurs in the southern (summer) hemisphere, arising near the pole and at mid-latitudes from cumulus updrafts triggered by surface heating and/or local methane sources, and at the north (winter) pole, resulting from the subsidence and condensation of ethane-rich air into the colder troposphere. General circulation models predict that this distribution should change with the seasons on a 15-year timescale, and that clouds should develop under certain circumstances at temperate latitudes ( approximately 40 degrees ) in the winter hemisphere. The models, however, have hitherto been poorly constrained and their long-term predictions have not yet been observationally verified. Here we report that the global spatial cloud coverage on Titan is in general agreement with the models, confirming that cloud activity is mainly controlled by the global circulation. The non-detection of clouds at latitude approximately 40 degrees N and the persistence of the southern clouds while the southern summer is ending are, however, both contrary to predictions. This suggests that Titan's equator-to-pole thermal contrast is overestimated in the models and that its atmosphere responds to the seasonal forcing with a greater inertia than expected.
Sébastien Rodriguez; Stéphane Le Mouélic; Pascal Rannou; Gabriel Tobie; Kevin H Baines; Jason W Barnes; Caitlin A Griffith; Mathieu Hirtzig; Karly M Pitman; Christophe Sotin; Robert H Brown; Bonnie J Buratti; Roger N Clark; Phil D Nicholson
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Nature     Volume:  459     ISSN:  1476-4687     ISO Abbreviation:  Nature     Publication Date:  2009 Jun 
Date Detail:
Created Date:  2009-06-04     Completed Date:  2009-06-10     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  678-82     Citation Subset:  -    
Laboratoire de Planétologie et Géodynamique, CNRS, UMR 6112, Université de Nantes, 2 rue de la Houssinière, 44000 Nantes, France.
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