Earth and Atmospheric Sciences, Department of


First Advisor

Adam L. Houston

Date of this Version

Summer 8-2019


Krull, A. J., 2019: The Role of Boundary-Parallel Vertical Wind Shear in Convection Initiation. M.S. Thesis, Department of Earth and Atmospheric Sciences, University of Nebraska-Lincoln.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science. Major: Earth and Atmospheric Sciences. Under the Supervision of Professor Adam L. Houston. Lincoln, Nebraska: August 2019

Copyright (c) 2019 Alexander J. Krull


Convection initiation (CI) remains a forecasting challenge for meteorologists. CI frequently occurs within the vicinity of some airmass boundary or density current. Airmass boundaries are favored areas of convergence, thus associated forced ascent facilitates CI. Features such as misocyclones often develop along the leading edge of airmass boundaries, favoring updraft formation and prompting alterations to the horizontal and vertical flow near the boundary. Airmass boundary characteristics and CI potential have been found to be sensitive to the environmental vertical wind shear. This affects propagation speed, convergence, and thus forced ascent along the leading edge. Previous studies have focused primarily on the boundary-normal component of the vertical wind shear vector, assessing changes in density current depth, propagation speed, and convergence. This experiment seeks to discover how airmass boundary characteristics and CI potential are impacted by changes to the boundary-parallel component to the vertical wind shear vector. Through idealized high-resolution simulations, this study finds there is sensitivity to changes in the boundary-parallel vertical wind shear vector that affects CI potential, due to alterations in propagation speed and vertical ascent. This sensitivity is dependent on the initial temperature perturbation of the density current. The results of these simulations and an explanation of the physical processes attributed to changes in the boundary-parallel vertical wind shear are discussed.

Advisor: Adam L. Houston