How Does Vertical Wind Shear Influence Entrainment in Squall Lines?

The influence of vertical wind shear on updraft entrainment in squall lines is not well understood. To address this knowledge gap, a suite of high-resolution idealized numerical model simulations of squall lines were run in various vertical wind shear (hereafter “shear”) environments to study the ef...

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Vydané v:Journal of the atmospheric sciences Ročník 78; číslo 6; s. 1931 - 1946
Hlavní autori: Mulholland, Jake P., Peters, John M., Morrison, Hugh
Médium: Journal Article
Jazyk:English
Vydavateľské údaje: Boston American Meteorological Society 01.06.2021
Predmet:
Boundary shear
Buoyancy
Convection lines
Deep convection
Dilution
Entrainment
ENVIRONMENTAL SCIENCES
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Mass flux
Mathematical models
Mesoscale systems
Meteorology & Atmospheric Sciences
Numerical models
Numerical simulations
Outflow
Simulation
Squall lines
Squalls
Updraft
Updrafts/downdrafts
Vertical velocities
Vertical wind shear
Wind
Wind shear
ISSN:0022-4928, 1520-0469
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Shrnutí:The influence of vertical wind shear on updraft entrainment in squall lines is not well understood. To address this knowledge gap, a suite of high-resolution idealized numerical model simulations of squall lines were run in various vertical wind shear (hereafter “shear”) environments to study the effects of shear on entrainment in deep convective updrafts. Low-level horizontal mass flux into the leading edge of the cold pool was strongest in the simulations with the strongest low-level shear. These simulations consequently displayed wider updrafts, less entrainment-driven dilution, and larger buoyancy than the simulations with comparatively weak low-level shear. An analysis of vertical accelerations along trajectories that passed through updrafts showed larger net accelerations from buoyancy in the simulations with stronger low-level shear, which demonstrates how less entrainment-driven dilution equated to stronger updrafts. The effects of upper-level shear on entrainment and updraft vertical velocities were generally less pronounced than the effects of low-level shear. We argue that in addition to the outflow boundary-shear interactions and their effect on updraft tilt established by previous authors, decreased entrainment-driven dilution is yet another beneficial effect of strong low-level shear on squall-line updraft intensity.
Bibliografia:ObjectType-Article-1
SourceType-Scholarly Journals-1
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SC0020104; AGS-1928666; AGS-1841674
USDOE Office of Science (SC)
National Science Foundation (NSF)
ISSN:0022-4928
1520-0469
DOI:10.1175/JAS-D-20-0299.1