Understanding extreme tornado events under future climate change through the pseudo-global warming methodology

Woods, Matthew James

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https://hdl.handle.net/2142/112982 Copy

Description

Title

Understanding extreme tornado events under future climate change through the pseudo-global warming methodology

Author(s)

Woods, Matthew James

Issue Date

2021-07-01

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

Trapp, Robert J

Committee Member(s)

• Lasher-Trapp, Sonia
• Sriver, Ryan

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)

• Tornado
• climate change
• pseudo global warming
• May 20 2013
• February 10 2013
• WRF
• CM1

Abstract

This study is a first step in determining how extreme tornado events may change under future anthropogenic climate change using the “pseudo global warming” (PGW) methodology. To properly apply this methodology, current-day extreme tornado events must be adequately simulated (the control; CTRL), and then simulated again with climate-change differences, or “deltas”, applied to the original 3D meteorological forcing. These climate change deltas represent differences in future and historical general circulation model projections from the coupled model intercomparison project-phase 5 (CMIP5). Several delta construction methods were employed to provide a larger ensemble and assess the importance of delta configuration. Given its classic supercellular nature, and extremely strong tornado (EF-5) with great societal impact, the 20 May 2013 tornado event in Moore, Oklahoma was one event chosen for application of the PGW methodology. Using high-resolution CTRL and PGW simulations using the Weather Research and Forecasting model (WRF), it was found that the convective storms under PGW are more numerous, but updraft velocities do not scale directly with future increases in convective available potential energy (CAPE). It was also found that instances of a baseline tornado proxy decreased in the PGW simulations, while instances of a high-end tornado proxy increased, indicating fewer but stronger tornadoes under PGW. The convective response also showed some sensitivity to the configuration of the climate change deltas, especially at upper thresholds of the parameters assessed. Separate WRF simulations of the 10 February 2013 tornado outbreak, which included an EF-4 tornado in Hattiesburg, Mississippi, were also conducted. Here, uniform sea-surface temperature (SST) perturbations were applied to the Gulf of Mexico to investigate the influence of SSTs on cool-season tornado events. Warmer SSTs were found to produce more favorable thermodynamic environments that manifested in increased convective coverage and intensity. Additionally, tornado proxy was more (less) numerous and intense in simulations with warmer (cooler) SSTs. To complement the WRF experiments for the 20 May 2013 and 10 February 2013 events, idealized cloud-resolving model simulations were conducted using Cloud Model 1 (CM1). These warm and cool-season events, respectively, were used to determine if the influence of climate change on extreme tornado events exhibits any seasonality. In the idealized simulations, despite smaller and shorter-lived supercells, assessment of “tornado power” suggests more powerful tornado-like vortices under PGW in both cases. This is consistent with the stronger tornado proxy found in the WRF PGW simulations.

Graduation Semester

2021-08

Type of Resource

Thesis

Permalink

http://hdl.handle.net/2142/112982

Copyright and License Information

Copyright 2021 Matthew Woods

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