Show simple item record

contributor authorYamaguchi, Takanobu
contributor authorRandall, David A
date accessioned2017-06-09T16:55:05Z
date available2017-06-09T16:55:05Z
date copyright2012/03/01
date issued2011
identifier issn0022-4928
identifier otherams-76473.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4218924
description abstracthe relative importance, for cloud-top entrainment, of the cooling rates due to longwave radiation, evaporation, and mixing was assessed through analysis of the results produced by a Lagrangian parcel-tracking model (LPTM) incorporated into a large-eddy simulation model. The LPTM predicts each parcel?s trajectory over time, using the resolved velocity simulated by the host model. An LPTM makes it possible to identify entrained parcels; this is almost impossible to do in an observational study.A nocturnal stratocumulus cloud was simulated over 4h using a 5-m horizontal grid spacing and a 2.5-m vertical grid spacing. At the start of the last hour of the simulation, over 40 million parcels were placed near the top of the inversion layer and then tracked. Parcel histories were analyzed to identify entrained parcels.Entrainment occurs in cloud holes, which occur in dry regions of sinking air. Entrainment into the mixed layer is regulated by buoyancy, which requires parcels to be precooled in the inversion layer, prior to entrainment. A mixing fraction analysis was used to separate the cooling due to longwave radiation, evaporation, and mixing. Results show that radiative and evaporative cooling are of comparable importance, but that mixing is by far the dominant cooling mechanism. The radiative cooling rate is strongly inhomogeneous, and only weak radiative cooling is found in regions of entrainment. Therefore, the entrained parcels experience less than the horizontal-mean radiative cooling. Although radiative cooling maintains the boundary layer turbulence, its direct effect on buoyancy of entrained parcels is modest.
publisherAmerican Meteorological Society
titleCooling of Entrained Parcels in a Large-Eddy Simulation
typeJournal Paper
journal volume69
journal issue3
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/JAS-D-11-080.1
journal fristpage1118
journal lastpage1136
treeJournal of the Atmospheric Sciences:;2011:;Volume( 069 ):;issue: 003
contenttypeFulltext


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record