Earth and Atmospheric Sciences, Department of
Matthew Van Den Broeke
Date of this Version
Gunkel, T., 2020: A Polarimetric Radar Analysis of Cold- and Warm-Based Supercells. M.S. thesis, Dept. of Earth and Atmospheric Sciences, University of Nebraska, 79 pp.
Polarimetric analyses of supercell thunderstorms have been increasingly common within the past decade, since operational polarimetric radar data became available in 2013. Although polarimetric signatures within supercell thunderstorms are well known, few have investigated variability in these signatures in differing environments. Polarimetric signatures can provide vital information regarding the microphysical characteristics and processes in supercell thunderstorms. Specific polarimetric signatures of interest are the differential reflectivity (ZDR) column, the low-level polarimetrically inferred hail core, and the ZDR arc. These signatures provide information regarding updraft characteristics, hailfall characteristics, and size sorting processes in the storm- relative inflow. Previous studies have identified these signatures and their microphysical significance, yet there is much to learn regarding how these characteristics differ between environments. The investigation of these signatures found within supercells characterized by differing cloud base temperatures will be discussed herein. These preliminary results can serve as an operational aid when observing supercell thunderstorms in a severe weather event, as these signatures can help to determine the potential for specific hazards, given specific environments. The environments of each type of supercell, along with the characteristics of their associated polarimetric signatures, can provide information about updraft intensity, hailfall characteristics, or tornado potential. This investigation finds that there are some significant differences, especially within the ZDR columns and the low- level polarimetrically inferred hail core, in the observed polarimetric signatures between different environments. All warm-based supercells exhibited a ZDR column, while many of the cold-based cases did not exhibit any column. Along with more warm-based cases exhibiting columns, they were also deeper than those observed in the cold-based cases. Cold-based supercells also exhibited much larger inferred hail cores than the warm-based supercells, which can be attributed to the cooler environments in which cold-based supercells are found. Finally, the ZDR arcs shown no large statistical differences across environments. This could be a consequence to the different thresholds utilized for identifying the arcs, along with different hailfall characteristics between environments.
Advisor: Matthew Van Den Broeke
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 Matthew Van Den Broeke. Lincoln, Nebraska: March 2020
Copyright 2020 Timothy J. Gunkel