M.S. (Master of Science)
Department of Geographic and Atmospheric Sciences
Rotating storms, or supercells, are frequent producers of significant tornadoes, hail, and nontornadic winds and an underappreciated genitor of extreme precipitation rates and flash floods. Little research has examined the precipitation contributions from supercells to the overall hydroclimate of the CONUS and, provided that these storms and their precipitation rates may shift in the future due to climate change, it is important to understand their characteristics from both historical and future perspectives. This research seeks to understand supercell precipitation characteristics across the CONUS using high-resolution, convection-permitting, dynamical-downscaled simulations for three, 15-year epochs. Epochs include a historical end-of-20th-century period (1990–2005) and two end-of-21st-century (2085–2100) scenarios for intermediate and pessimistic greenhouse gas concentration trajectories. Simulated updraft helicity, which measures the corkscrew flow within a storm’s updraft, is used as a proxy for supercells. An algorithm tracks and catalogs updraft helicity swaths, which, when buffered, is used to acquire the precipitation from supercells. The historic epoch provides a baseline climatology of simulated supercell precipitation, which is then compared against the two future epochs. Despite their relatively small size, supercells provide critical precipitation to the Wheat and Corn Belts, large expanses of CONUS pasture and rangeland, regional aquifers, and a number of large river basins. Many areas in the central CONUS receive upwards of 3-6% (5-8%) of their annual (warm-season) precipitation from these storms. Results suggest that precipitation contribution from supercells will decrease across most of the Great Plains with robust increases likely across the South Central and Southeast regions in the future. Supercell precipitation rates are expected to increase for large portions of the CONUS by the end of the 21st century, which suggests a growing threat for flash floods from these storms. Ultimately, this research provides an initial perspective on the magnitude of supercell precipitation and potential changes to this important hydrologic input, to assist water-sensitive industries, private and public insurance markets, agriculture entities, as well as inform plans to mitigate, and build resilience for rapid environmental and societal change.
Zeeb, Aaron, "Historical and Future Projections of Supercell Precipitation Contributions to the Hydroclimate of the United States" (2023). Graduate Research Theses & Dissertations. 7363.
Northern Illinois University
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