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The role of low-level clouds in the West African monsoon system

Kniffka, Anke; Knippertz, Peter; Fink, Andreas H.

Abstract:
Realistically simulating the West African monsoon system still poses a substantial challenge to state-of-the-art weather and climate models. One particular issue is the representation of the extensive and persistent low-level clouds over southern West Africa (SWA) during boreal summer. These clouds are important in regulating the amount of solar radiation reaching the surface, but their role in the local energy balance and the overall monsoon system has never been assessed. Based on sensitivity experiments using the ICON model for July 2006, we show for the first time that rainfall over SWA depends logarithmically on the optical thickness of low clouds, as these control the diurnal evolution of the planetary boundary layer, vertical stability and finally convection. In our experiments, the increased precipitation over SWA has a small direct effect on the downstream Sahel, as higher temperatures due to increased surface radiation are accompanied by decreases in low-level moisture due to changes in advection, leading to almost unchanged equivalent potential temperatures in the Sahel. A systematic comparison of simulations with and without convective parameterization reveals agreement in the direction of the precipitation signal but larger sensitivity for explicit convection. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000091365
Veröffentlicht am 20.02.2019
Originalveröffentlichung
DOI: 10.5194/acp-19-1623-2019
Scopus
Zitationen: 1
Web of Science
Zitationen: 1
Coverbild
Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung - Forschungsbereich Troposphäre (IMK-TRO)
Publikationstyp Zeitschriftenaufsatz
Jahr 2019
Sprache Englisch
Identifikator ISSN: 1680-7324
urn:nbn:de:swb:90-913657
KITopen-ID: 1000091365
HGF-Programm 12.01.02 (POF III, LK 01)
Erschienen in Atmospheric chemistry and physics
Band 19
Heft 3
Seiten 1623–1647
Bemerkung zur Veröffentlichung Gefördert durch den KIT-Publikationsfonds
Vorab online veröffentlicht am 07.02.2019
Nachgewiesen in Web of Science
Scopus
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