The spatial area and other attributes of GOES-16 overshooting tops as indicators of potential hail

Christo, Gabrielle

Permalink

https://hdl.handle.net/2142/124379 Copy

Description

Title

The spatial area and other attributes of GOES-16 overshooting tops as indicators of potential hail

Author(s)

Christo, Gabrielle

Issue Date

2024-04-30

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

Trapp, Robert J

Committee Member(s)

• Nesbitt, Stephen
• Di Girolamo, Larry

Department of Study

Climate Meteorology & Atm Sci

Discipline

Atmospheric Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• hail
• overshooting tops
• overshooting top area
• overshooting top depth
• overshooting top volume

Abstract

Each year hail contributes to most of the aggregated loss from severe weather-induced property and crop damages in the U.S. Efforts to mitigate these damages require methods to predict severe-hail occurrence and assess severe-hail risk. One such method relies on weather radar, which is known to overestimate hail size. Another method relies on weather satellites. Prior studies using idealized thunderstorm simulations suggest that storms that generate large hail should exhibit deep and wide overshooting tops (OTs), which are a manifestation of a convective updraft that penetrates through the tropopause into the lower stratosphere. This work builds off these and related studies to explore possible relationships between OT characteristics and hail size observed at the ground. All hail reports from 2018 through 2022 across the contiguous U.S were assigned to 0.5° x 0.5° latitude-longitude grid cells. The largest hail report in each grid cell for every hour was selected. An OT detection algorithm was applied to GOES-16 data and used to find the nearest OT to each selected report. Overshooting area (OTA), overshooting top depth (OTD), and overshooting top volume (OTV) were quantified and statistically related to observed hail size at the ground. It was found that the maximum area of an OT during the ±15 min analysis window relative to its associated hail report tended to exhibit a negative, statistically insignificant relationship with hail size (R = -0.57, P = 0.11); this negative relationship was also reflected in OTV (R = -0.47, P = 0.2). In contrast, the mean OTA during the analysis window exhibited a positive, statistically insignificant relationship with hail size (R = 0.18, P = 0.63). Results also showed a positive, statistically significant relationship between hail size and maximum and mean OTD (R = 0.94, P = 2.01x10-4). The OTD as well as OTA associated with relatively smaller hail exhibited higher variability during the analysis window than did the OTA associated with relatively larger hail. To explore possible dependencies of these results on hail reports, MESH was used as a report proxy. It was found that MESH had a positive, statistically insignificant relationship with maximum OTA (R = 0.31, P =0.45), and a negative, statistically insignificant relationship with mean OTA (R = -0.18, P = 0.65). As with hail reports, MESH had a positive, statistically significant relationship with maximum and mean OTD (R = 0.81, P = 0.015). To additionally explore possible dependencies of the results on convective mode, a supercell dataset was used. It was found that satellite-based OTA relationships with reported hail size for supercells were generally negative and statistically insignificant, and thus consistent with results for all reports and thus all convective morphologies. The relationship between radar-derived OTA and hail size was positive, but statistically insignificant (R = 0.3, P = 0.5). Finally, to explore possible relationships between reported hail size and midlevel updraft area, a radar reflectivity based proxy for updraft was used. The linear relationships between hail size and the nearest and maximum reflectivity core areas were found to be positive and statistically significant (R = 0.87, P = 2.37x10-3). The application of these OT-hail results for hail-risk assessment and operational hail prediction would benefit from analyses of more cases and an inclusion of environmental conditions known to support hail occurrence.

Graduation Semester

2024-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2024 Gabrielle Christo

Owning Collections