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contributor authorNeggers, R. A. J.
contributor authorSiebesma, A. P.
contributor authorLenderink, G.
contributor authorHoltslag, A. A. M.
date accessioned2017-06-09T17:26:34Z
date available2017-06-09T17:26:34Z
date copyright2004/11/01
date issued2004
identifier issn0027-0644
identifier otherams-85352.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4228790
description abstractThree closure methods for the mass flux at cloud base in shallow cumulus convection are critically examined for the difficult case of a diurnal cycle over land. The closure methods are first evaluated against large-eddy simulations (LESs) by diagnosing all parameters appearing in the closure equations during simulations of two different observed diurnal cycles of shallow cumulus. This reveals the characteristic behavior of each closure mechanism purely as a result of its core structure. With these results in hand the impact of each closure on the development of the cloudy boundary layer is then studied by its implementation in an offline single-column model of a regional atmospheric climate model. The LES results show that the boundary layer quasi-equilibrium closure typically overestimates the cloud-base mass flux after cloud onset, due to the neglect of significant moisture and temperature tendencies in the subcloud layer. The convective available potential energy (CAPE) adjustment closure is compromised by its limitation to compensating subsidence as the only CAPE breakdown mechanism and the use of a constant adjustment time scale. The closure method using the subcloud convective vertical velocity scale gives the best results, as it catches the time development of the cloud-base mass flux as diagnosed in LES.
publisherAmerican Meteorological Society
titleAn Evaluation of Mass Flux Closures for Diurnal Cycles of Shallow Cumulus
typeJournal Paper
journal volume132
journal issue11
journal titleMonthly Weather Review
identifier doi10.1175/MWR2776.1
journal fristpage2525
journal lastpage2538
treeMonthly Weather Review:;2004:;volume( 132 ):;issue: 011
contenttypeFulltext


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