Controls on the widths of intense convective updrafts

 
Poster PDF

Authors

Robert Jeff Trapp — University of Illinois at Urbana-Champaign
Sonia LasherTrapp — UIUC
Steve Nesbitt — University of Illinois at Urbana-Champaign
Geoff Marion — UIUC

Category

Deep convective clouds, including aerosol interactions

Description

Motivated by connections between initial updraft size and subsequent cold-pool depth, this research seeks to address questions regarding the controls on the width of intense convective updrafts. Here we use CM1, a non-hydrostatic, fully compressible, 3D cloud-resolving model. The CM1 simulations assume an initially horizontally homogenous, but vertically stratified, environment. An analytic sounding describes the environment; the sounding is characteristic of a warm-season convective environment within the continental midlatitudes. Convective motions within the initially quiescent environment are initiated through the traditional ways (e.g., warm bubbles) employed in idealized cloud modeling. Our idealized experiments are designed to explore the convective response to the length scales of such forcing. We find that when the environment lacks vertical wind shear, the updraft size (horizontal area) depends directly on the scale of the forcing. However, when the environment has vertical wind shear, the resultant updraft size becomes relatively insensitive to the forcing, and instead is positively correlated with quantifications of vertical wind shear, such as environmental helicity. These results have important implications on the assignment of “plume” sizes in convective parameterization schemes, which tend not to account for the effects of vertical wind shear.