Study of Convective Hazards under Anthropogenic Climate Change using innovative approaches

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It is difficult to assess how severe thunderstorms and tornadoes may change in a warmer climate because various factors dictate the strength and frequency of hail, severe winds, and tornadoes. Prior efforts to determine potential changes in severe weather have been based on indirect and statistical measures of the likelihood for severe weather. In this project, the research team will instead investigate historical severe weather events and then modify their environments to match outputs from climate model simulations. The result of the project will be a better physical understanding of the potentials causes and frequency of these hazards. An additional effort will use population and housing data to help estimate the impacts of severe weather hazards in a warmer climate, thereby addressing human vulnerability to these hazards. Graduate students would be involved in the project, ensuring the professional development of the next generation of researchers.The research team will conduct a numerical modeling study using the pseudo-global-warming (PGW) approach, wherein a variety of historical convective-weather events will be simulated both in their true 4D environment as well as in a 4D environment modified by a measure of climate change. The research team argues that past work, including their own, on the topic has been limited to the use of environmental parameters and dynamic downscaling, both of which have significant drawbacks. The PGW technique provides a flexible framework for experimentation and examination of cause and effect in dynamical and microphysical processes and allows for the use of higher resolutions and multiple realizations of a single case. The project will use the WRF-ARW with input from several of the CMIP-5 and CMIP-6 models for the climate change delta. Three hypotheses will be addressed: 1) Representative and characteristic warm- (cool-) season tornadoes will be less (more) intense under anthropogenic climate change (ACC), 2) Representative damaging straight-line wind events will be more intense, but relatively shorter-lived, under ACC, and 3) Despite decreases in vertical wind shear and increases in the height of the melting level, hailfall swath area and hailstone size at the ground will generally increase under ACC.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.