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contributor authorBrown, Matthew
contributor authorNowotarski, Christopher J.
date accessioned2019-10-05T06:51:07Z
date available2019-10-05T06:51:07Z
date copyright3/11/2019 12:00:00 AM
date issued2019
identifier otherJAS-D-18-0216.1.pdf
identifier urihttp://yetl.yabesh.ir/yetl1/handle/yetl/4263623
description abstractAbstractThis paper reports on results of idealized numerical simulations testing the influence of low-level humidity, and thus lifting condensation level (LCL), on the morphology and evolution of low-level rotation in supercell thunderstorms. Previous studies have shown that the LCL can influence outflow buoyancy, which can in turn affect generation and stretching of near-surface vertical vorticity. A less explored hypothesis is tested: that the LCL affects the relative positioning of near-surface circulation and the overlying mesocyclone, thus influencing the dynamic lifting and intensification of near-surface vertical vorticity. To test this hypothesis, a set of three base-state thermodynamic profiles with varying LCLs are implemented and compared over a variety of low-level wind profiles. The thermodynamic properties of the simulations are sensitive to variations in the LCL, with higher LCLs contributing to more negatively buoyant cold pools. These outflow characteristics allow for a more forward propagation of near-surface circulation relative to the midlevel mesocyclone. When the mid- and low-level mesocyclones become aligned with appreciable near-surface circulation, favorable dynamic updraft forcing is able to stretch and intensify this rotation. The strength of the vertical vorticity generated ultimately depends on other interrelated factors, including the amount of near-surface circulation generated within the cold pool and the buoyancy of storm outflow. However, these simulations suggest that mesocyclone alignment with near-surface circulation is modulated by the ambient LCL, and is a necessary condition for the strengthening of near-surface vertical vorticity. This alignment is also sensitive to the low-level wind profile, meaning that the LCL most favorable for the formation of intense vorticity may change based on ambient low-level shear properties.
publisherAmerican Meteorological Society
titleThe Influence of Lifting Condensation Level on Low-Level Outflow and Rotation in Simulated Supercell Thunderstorms
typeJournal Paper
journal volume76
journal issue5
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/JAS-D-18-0216.1
journal fristpage1349
journal lastpage1372
treeJournal of the Atmospheric Sciences:;2019:;volume 076:;issue 005
contenttypeFulltext


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