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A one-dimensional cloud model with trimodal convective outflow

dc.contributor.authorFolkins, Ianen_US
dc.date.accessioned2013-06-19T15:22:31Z
dc.date.available2013-06-19T15:22:31Z
dc.date.issued2009en_US
dc.description.abstractThe author describes a one-dimensional cloud model designed to investigate the relationships between stratiform downdrafts, congestus outflow, stability, and relative humidity in the tropical lower troposphere. In the tropics, the climatological lapse rate varies with height below the melting level in a way that is inconsistent with the assumptions of either moist pseudoadiabatic or reversible adiabatic ascent. This anomalous variation is referred to as the melting-level stability anomaly (MLSA). It is argued that the MLSA is caused by a transition from static to dynamic downdrafts at the melting level. Above the melting level, evaporation of precipitation cools and moistens the tropical atmosphere but does not generate downdraft parcels with sufficient negative buoyancy to descend between model levels. Below the melting level, the evaporative cooling associated with stratiform precipitation is strong enough to overcome the stability of the atmosphere and generate a convective-scale circulation. The vertical descent within these downdrafts induces a compensatory ascent in the background atmosphere that changes the overall cooling-to-moistening downdraft ratio. The inclusion of this stratiform downdraft circulation brings the modeled lapse rate and relative humidity profiles into simultaneous agreement with observations. The transition from static to dynamic downdrafts is triggered, in the model, by imposed increases in the amount of rain falling outside clouds, in the out-of-cloud rain rate, and in the vertical coherence of the rain shafts. The destabilization of the lower tropical atmosphere triggered by the stratiform circulation affects the development of convective clouds. In particular, the melting-level stability anomaly increases detrainment near the melting level and gives rise to the congestus mode. 2009 American Meteorological Society.en_US
dc.identifier.citationFolkins, Ian. 2009. "A one-dimensional cloud model with trimodal convective outflow." Journal of Climate 22(23): 6437-6455.en_US
dc.identifier.issn08948755en_US
dc.identifier.issue23en_US
dc.identifier.startpage6437en_US
dc.identifier.urihttp://dx.doi.org/10.1175/2009JCLI3134.1en_US
dc.identifier.urihttp://hdl.handle.net/10222/24133
dc.identifier.volume22en_US
dc.publisherAmerican Meteorological Societyen_US
dc.relation.ispartofJournal of Climateen_US
dc.subjectMeltingen_US
dc.subjectAtmospheric humidityen_US
dc.subjectAtmosphericsen_US
dc.subjectCloudsen_US
dc.subjectEvaporationen_US
dc.subjectEvaporative cooling systemsen_US
dc.subjectMoistureen_US
dc.subjectRainen_US
dc.subjectStabilityen_US
dc.subjectTropical engineeringen_US
dc.subjectTropicsen_US
dc.titleA one-dimensional cloud model with trimodal convective outflowen_US
dc.typearticleen_US

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