Understanding Satellite-Era Trends in Extratropical Circulation Extremes

Extreme weather events such as heatwaves, downpours, and damaging winds have major impacts on lives and livelihoods. While increases in heat and precipitation extremes are well documented, much less is known about how atmospheric circulation extremes, for instance near-surface extreme wind associated with weather systems, have changed in recent decades and how these changes influence regional weather hazards. This project aims to improve scientific understanding of how circulation extremes in the middle latitudes have changed during the satellite era and how they are connected to heat and precipitation extremes. The research will combine observations, theory, physics-based Earth system models, and emerging Artificial Intelligence models to better understand how and why these extreme events are changing regionally. The project will also support the training of two PhD students and an undergraduate student through the Leadership Alliance Summer Research Early Identification Program, helping to train the next generation of scientists. The goal of this project is to establish a quantitative, mechanistic understanding of satellite-era trends in extratropical circulation extremes and their relationship to thermodynamic extremes. The investigators hypothesize that moist thermodynamic processes linked to the Clausius-Clapeyron relation play a leading-order role in shaping trends in upper-level jet stream extremes and wind shear, and near-surface extreme wind associated with weather systems. The research team will analyze trends in observations and reanalysis products and compare them to Earth system model simulations, including large ensembles, and emerging AI models. The project will develop new dynamical scaling theories based on moist thermal wind balance and test them across a hierarchy of Earth system models. In addition, Earth system model atmospheric nudging experiments will be used to isolate the contributions of circulation, temperature, and humidity trends to observed changes in heat, precipitation, and circulation extremes. This multi-pronged approach will improve understanding of how atmospheric circulation extremes have changed in the satellite era and their role in regional weather extremes. 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. NSF Award ID: 2607380 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Tiffany Shaw | Institution: University of Chicago, CHICAGO, IL | Award Amount: $942,543 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2607380 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2607380.html