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Article Dans Une Revue Geophysical Research Letters Année : 2021

Shear‐Convection Interactions and Orientation of Tropical Squall Lines

Résumé

Abstract Squall lines are known to be the consequence of the interaction of low-level shear with cold pools associated with convective downdrafts. Also, as the magnitude of the shear increases beyond a critical shear, squall lines tend to orient themselves. The existing literature suggests that this orientation reduces incoming wind shear to the squall line, and maintains equilibrium between wind shear and cold pool spreading. Although this theory is widely accepted, very few quantitative studies have been conducted on supercritical regime especially. Here, we test this hypothesis with tropical squall lines obtained by imposing a vertical wind shear in cloud resolving simulations in radiative convective equilibrium. In the sub-critical regime, squall lines are perpendicular to the shear. In the super-critical regime, their orientation maintain the equilibrium, supporting existing theories. We also find that as shear increases, cold pools become more intense. However, this intensification has little impact on squall line orientation. Plain Language Summary A squall line is a line of thunderstorms associated with heavy precipitation and only a well-informed meteorologist would notice that these convective bands are sometimes oriented with respect to the wind direction. Yet this is the case, and in this study we seek to understand what sets tropical squall lines orientation, and why. Using numerical simulations, we show quantitatively that the orientation of the squall lines restores the equilibrium between the wind and the cold pool spreading, providing for the first time a quantitative validation of existing theories.
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Dates et versions

hal-03559929 , version 1 (07-02-2022)

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Sophie Abramian, Caroline Muller, Camille Risi. Shear‐Convection Interactions and Orientation of Tropical Squall Lines. Geophysical Research Letters, 2021, 49 (1), ⟨10.1029/2021gl095184⟩. ⟨hal-03559929⟩
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