How does vertical wind shear influence entrainment in squall lines?

Jake P. Mulholland, John M. Peters, Hugh Morrison

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1931-1946
Number of pages16
JournalJournal of the Atmospheric Sciences
Issue number6
StatePublished - Jun 2021

All Science Journal Classification (ASJC) codes

  • Atmospheric Science


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