Estimating midlevel updraft characteristics and severe weather intensity through the lens of overshooting tops

Grover, Maxwell Austin

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https://hdl.handle.net/2142/110583 Copy

Description

Title

Estimating midlevel updraft characteristics and severe weather intensity through the lens of overshooting tops

Author(s)

Grover, Maxwell Austin

Issue Date

2021-04-28

Director of Research (if dissertation) or Advisor (if thesis)

Trapp, Robert J

Department of Study

Atmospheric Sciences

Discipline

Atmospheric Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Deep Convection
• Thunderstorms
• Overshooting Tops
• South America
• Severe Weather
• Updrafts

Abstract

Cloud resolving model simulations show that the horizontal area of “convective overshoots” at the top of deep convective storms relates strongly to the area of the associated updraft core within the middle troposphere. Observational support of such overshooting top area (OTA) – updraft relationships was found in this thesis using coincident observations of (overshooting tops) OTs and updrafts collected in three cases during the RELAMPAGO field campaign in Córdoba province, Argentina. The RELAMPAGO data revealed that different convective morphologies had different OT characteristics, with long-lived, large OTs found in association with a supercell case, smaller, shorter-lived OTs found with a multicell case, and finally, short-lived, large OTs found with a MCS case. In general, the convective storms with wide, deep, and intense updrafts tended to be associated with large and deep OTs. The results were used to explore the hypothesis that characteristics of satellite-identified OTs can be used to quantify midtropospheric updraft area as well as intensity and vertical mass flux. Using radar-retrieved updraft area and corresponding calculations, a scaling factor and simple approach was used to estimate distributions of updraft core radii using OTs during the three cases. The estimated updraft core widths were within 1-2 km of previous measurements of updraft width in midlatitude regions. This connection between midlevel updraft area and OTA was also used to estimate the intensity of severe convective weather phenomena, expanding upon a previous study that was focused solely on tornado intensity. Reports of severe hail, severe straight-line winds, and tornadoes were paired with their respective OT events, and then the peak intensity of severe weather and peak OTA were determined. It was shown that OTA, as well as OT depth, have some skill in distinguishing significant from nonsignificant hail size, wind intensity, and tornado intensity. OTA distributions from both a supercell and MCS were used as a case study to evaluate the ability to infer updraft characteristics from OTs.

Graduation Semester

2021-05

Type of Resource

Thesis

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http://hdl.handle.net/2142/110583

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Copyright 2021 Maxwell Grover

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