Earth and Atmospheric Sciences, Department of

 

First Advisor

Adam L. Houston

Second Advisor

Jason Keeler

Third Advisor

Mark Anderson

Date of this Version

11-2023

Citation

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, November 2023

Comments

Copyright 2023, Charles Kropiewnicki

Abstract

A Mesoscale Airmass with High Theta-E (MAHTE) is a narrow region of larger theta-e located on the cool side of an airmass boundary. MAHTEs typically possesses higher CAPE than the warm side of the boundary, creating a more favorable environment for severe convection. MAHTEs can also be characterized by larger low-level shear and lower LCLs and may also have a propensity for supporting tornadogenesis. The majority of MAHTE research to date has been comprised of case studies, and the prevalence of MAHTEs is not well understood. This project fills that knowledge gap by creating a climatology of MAHTE occurrence. This climatology has been created through the identification of MAHTEs in time series of ASOS data from across the continental United States. The identification algorithm has been verified using West Texas Mesonet data, providing high temporal and spatial resolution that the ASOS network cannot achieve. MAHTEs from over 900 ASOS stations have been identified and compiled into a national climatology.

The climatology shows that MAHTEs are most frequent in the desert southwest and the Florida panhandle. The frequency and characteristics of MAHTEs are highly variable, both in time and space, and this variability affects the potential impact any MAHTE may have. MAHTEs introduce more favorable conditions for supercells, with higher CAPE (728 ± 523 J kg-1) and 0-6 bulk wind differential (1.9 ± 4.4 m s-1) than their environments; however, this is only relevant if the environment also supports deep convection initiation. MAHTEs identified near a coast were commonly associated with boundaries moving on-shore, suggesting that these coastal MAHTEs are related to ocean/sea breezes.

Advisor: Adam L. Houston

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