Understanding the impact of the lowermost stratospheric thermodynamic environment on observed overshooting top characteristics

Berman, Melinda T

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https://hdl.handle.net/2142/120446 Copy

Description

Title

Understanding the impact of the lowermost stratospheric thermodynamic environment on observed overshooting top characteristics

Author(s)

Berman, Melinda T

Issue Date

2023-05-02

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

• Trapp, Robert J
• Nesbitt, Stephen W

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)

• Overshooting top
• stratosphere
• thermodynamics

Abstract

Overshooting tops (OTs) are manifestations of deep convective updrafts that extend above the tropopause into the stratosphere. They can induce dynamic perturbations and result in irreversible transport of aerosols, smoke, water vapor and other mass from the troposphere into the stratosphere, thereby impacting the chemical composition of the stratosphere. These and other effects of OTs depend on their characteristics such as depth and area, both of which are understood to relate to midlevel updraft structure. Less understood is how static stability in the lowermost stratosphere (LMS) potentially modifies these OT characteristics, thus motivating the current study. The LMS static stability and observed OT characteristics are quantified and compared using a combination of reanalysis data, observed rawinsonde data and geostationary satellite data. A modest relationship between OT depth and LMS lapse rate (R = 0.48) and Brunt-Väisälä frequency (R = -0.43) is found, implying that OT depth is reduced with an increasingly stable LMS. In contrast, no relationship (R ~ 0) is found between OT area and LMS static stability, implying that OT area is controlled primarily by midlevel updraft area. These relationships may be useful in describing mid- and low-level storm dynamics from satellite-observed characteristics of OTs in near real-time. Idealized model simulations using the Bryan Cloud Model 1 (CM1) are used to help interpret these relationships. Modeling results for OT depth are consistent with observed behavior, while near storm top area modeling results are somewhat consistent with observed OT area trends.

Graduation Semester

2023-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/120446

Copyright and License Information

Copyright 2023 Melinda Berman

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