The effect of cloud shading on squall lines: a numerical simulation study
Open Access
Author:
Oberthaler, Andrew Joseph
Graduate Program:
Meteorology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 29, 2011
Committee Members:
Paul Markowski, Thesis Advisor/Co-Advisor Paul Markowski, Thesis Advisor/Co-Advisor
Keywords:
anvil squall line radiative transfer
Abstract:
Frame and Markowski (2010) have demonstrated the feasibility of using the tilted independent pixel approximation (TIPA) to account for three-dimensionality of cloud shading effects in idealized numerical simulations of supercells in which radiative transfer effects were included (in addition to surface fluxes, which couple the surface temperature forcing to an atmospheric response). This thesis examines the results of simulations of a long-lived squall line in which cloud shading effects are included using the TIPA. The simulations are compared to control simulations that also include surface fluxes but do not experience cloud shading effects. In the simulations with cloud shading, particularly under the leading anvil, the cooling and stabilization of the lower boundary layer reduces vertical mixing and gradients in buoyancy promote generation of negative environmental horizontal vorticity, both of which alter the low-level vertical wind shear in the inflow relative to the control simulations. It will be shown that the modifications of the hodograph and squall-line structure depend on the initial ground-relative wind profile.
