| Precipitation-generated oscillations in open cellular cloud fields. | |
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MedLine Citation:
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PMID: 20703303 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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Cloud fields adopt many different patterns that can have a profound effect on the amount of sunlight reflected back to space, with important implications for the Earth's climate. These cloud patterns can be observed in satellite images of the Earth and often exhibit distinct cell-like structures associated with organized convection at scales of tens of kilometres. Recent evidence has shown that atmospheric aerosol particles-through their influence on precipitation formation-help to determine whether cloud fields take on closed (more reflective) or open (less reflective) cellular patterns. The physical mechanisms controlling the formation and evolution of these cells, however, are still poorly understood, limiting our ability to simulate realistically the effects of clouds on global reflectance. Here we use satellite imagery and numerical models to show how precipitating clouds produce an open cellular cloud pattern that oscillates between different, weakly stable states. The oscillations are a result of precipitation causing downward motion and outflow from clouds that were previously positively buoyant. The evaporating precipitation drives air down to the Earth's surface, where it diverges and collides with the outflows of neighbouring precipitating cells. These colliding outflows form surface convergence zones and new cloud formation. In turn, the newly formed clouds produce precipitation and new colliding outflow patterns that are displaced from the previous ones. As successive cycles of this kind unfold, convergence zones alternate with divergence zones and new cloud patterns emerge to replace old ones. The result is an oscillating, self-organized system with a characteristic cell size and precipitation frequency. |
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Authors:
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Graham Feingold; Ilan Koren; Hailong Wang; Huiwen Xue; Wm Alan Brewer |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Nature Volume: 466 ISSN: 1476-4687 ISO Abbreviation: Nature Publication Date: 2010 Aug |
Date Detail:
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Created Date: 2010-08-12 Completed Date: 2010-10-04 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0410462 Medline TA: Nature Country: England |
Other Details:
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Languages: eng Pagination: 849-52 Citation Subset: - |
Affiliation:
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NOAA Earth System Research Laboratory (ESRL), Chemical Sciences Division, Boulder, Colorado 80305, USA. graham.feingold@noaa.gov |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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