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Changes in four decades of near-CONUS tropical cyclones in an ensemble of 12km thermodynamic global warming simulations

Presentation Date
Friday, December 15, 2023 at 9:05am - Friday, December 15, 2023 at 9:16am
MC - 3005 - West



In this presentation, we evaluate tropical cyclones (TCs) simulated in the thermodynamic global warming (TGW) simulations completed as part of the IM3 / HyperFACETS project. The simulations were completed using the Weather and Research Forecasting Model (WRF) at 12km grid spacing and were forced by the ERA5 reanalysis to provide a 40-year historical (1980-2019) control run. In addition, a set of future scenarios spanning a range of plausible changes in future climate (defined across both climate models and emission scenarios) were generated using thermodynamic deltas applied to the lateral boundary conditions and forcing. We curate a dataset of opportunity: exact 1-to-1 matches of every historical TC over the 40-year record that can be detected by TempestExtremes (guided by National Hurricane Center best track data) over our domain in all simulations. This analysis yields approximately 4,500 6-hourly snapshots in the control, with a corresponding "sibling" in each counterfactual.

When paired, we find that total precipitable water unsurprisingly increases for nearly every snapshot in the historical record, regardless of warming level, storm location, or intensity. We find that precipitation, measured as storm mean or maximum rate, increases in only approximately 65-80% of all TC snapshots, even for the highest warming level, suggesting a reduction in precipitation efficiency. However, in events that become wetter, the maximum precipitation rate tends to exhibit super-Clausius-Clapeyron scaling. Stronger storms show a reduction in the radius of maximum wind but little changes in the radii of weaker winds, implying a tightening of the pressure gradient in the storm core and a small, but noticeable, increase in maximum wind speeds. We find that the fraction of TCs undergoing rapid intensification or rapid weakening both increase across all warming simulations, which may imply changes in the predictability of TC intensity under future warming scenarios. Other results are discussed and we contextualize some of the strengths and weaknesses of the TGW approach for evaluating potential changes in TC hazards and impacts.

Funding Program Area(s)