The Influence of Ground-Relative Flow and Friction on Near-Surface Storm-Relative Helicity

Abstract Recent studies have highlighted the importance of near-ground storm-relative helicity (SRH) in supercell and tornado processes and how surface friction can play a role. In this study, we use an analytical approach to examine how uniform changes to the ground-relative wind profile above the...

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Bibliographic Details
Published inJournal of the atmospheric sciences Vol. 78; no. 7; pp. 2135 - 2142
Main Authors Flournoy, Matthew D., Rasmussen, Erik N.
Format Journal Article
LanguageEnglish
Published Boston American Meteorological Society 01.07.2021
Subjects
Friction
Helicity
Influence
Movement
Shear
Storm motion
Storms
Supercells
Thunderstorms
Tornadoes
Wind profiles
Wind shear
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Summary:Abstract Recent studies have highlighted the importance of near-ground storm-relative helicity (SRH) in supercell and tornado processes and how surface friction can play a role. In this study, we use an analytical approach to examine how uniform changes to the ground-relative wind profile above the near-ground layer influence SRH within the near-ground layer. We show how the ground-relative influence of surface friction alters the near-ground shear profile. For idealized semicircular and straight shear profiles, increasing preexisting ground-relative flow above the near-ground layer yields increasing SRH. The magnitude of the SRH increase is sensitive to storm motion, with more deviant motion yielding greater SRH increases given the same increase in ground-relative flow. Supercells may be more susceptible to storm-induced SRH enhancements given their deviant motion and ability to increase ground-relative flow in the background environment.
ISSN:0022-4928
1520-0469
DOI:10.1175/JAS-D-20-0320.1