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While tropical cyclone (TC) and heatwave (HW) compound hazard extremes are rare in the historical record, they have been recently emerging and are expected to become more frequent under future climate projections. Joint TC-HW hazards can exacerbate heat stress felt by residents, particularly in densely populated urban communities or areas suffering from storm-related power outages. The Princeton Urban Canopy Model (PUCM) has been used to evaluate heatwave conditions in urban environments, but has yet to be used to model joint TC-HW conditions. In this study, we model joint TC-HW hazards by adjusting the surface energy and water budgets of the PUCM to account for TC flood and extreme wind hazards. We investigate joint hazard interactions during Hurricane Laura (2020) using the Weather Research and Forecasting model (WRF) to simulate both Laura's wind field to drive subsequent hydrodynamic modeling of inundation and post-storm atmospheric conditions. The WRF and hydrodynamic modeling results are then used to drive the PUCM to assess the interaction of joint flooding, wind, and heat and their impacts on the city of Lake Charles in Louisiana. Results show that accounting for TC inundation up to a week after landfall can cause over 3°C reductions in daytime heat stress and 1.5°C increases in nighttime heat stress compared to simulations that ignore the presence of flooding. Accounting for defoliation from extreme TC winds can increase maximum nighttime heat stress by more than 4°C. 

Coastal flooding from tropical cyclone (TC)‐induced storm surges is among the most devastating natural hazards in the US. Accurately quantifying storm surge hazards is crucial for risk mitigation and climate adaptation. In this study, we conduct climatology‐hydrodynamic modeling to estimate TC surge hazards along the US northeast coastline under future climate scenarios. In this methodology, we generate synthetic TCs for the northeastern US to drive a hydrodynamic model (ADCIRC) to simulate storm surges. Observing their significant effect on storm surge, for the first time, we bias‐correct landfall angles of synthetic TCs, in addition to bias‐correcting their frequency and intensity. Our findings show that under the combined effects of sea level rise (SLR) and TC climatology change, historical 100‐year extreme water levels (EWLs) along the US northeast coastline would occur annually at the end of the century in both SSP2‐4.5 and SSP5‐8.5 emissions scenarios. 500‐year EWLs are also projected to occur every 1–60 (1–20) years under SSP2‐4.5 (SSP5‐8.5). SLR is the dominant factor in the dramatic changes in the EWLs. However, while in higher latitudes () TC climatology change modestly affect EWLs ( contribution for 100‐year and for 500‐year EWL changes), in lower latitudes the impact is more significant (up to 40% contribution to 100‐year and 55% for 500‐year EWL changes). Extending previous methods, the physics‐based probabilistic framework presented here can be applied to project future coastal flood hazards under the effects of SLR and storm climatology change for any TC‐prone region. 

Compound flooding, the concurrence of multiple flooding mechanisms such as storm surge, heavy rainfall, and riverine flooding, poses a significant threat to coastal communities. To mitigate the impacts of compound flooding, forecasts must represent the variability of flooding drivers over a wide range of spatial scales while remaining timely. One approach to develop these forecasts is through subgrid corrections, which utilize information at smaller scales to “correct” water levels and current velocities averaged over the model scale. Recent studies have shown that subgrid models can improve both accuracy and efficiency; however, existing models are not able to account for the dynamic interactions of hydrologic and hydrodynamic drivers and their contributions to flooding along the smallest flow pathways when using a coarse resolution. Here, we have developed a solver called CoaSToRM (Coastal Subgrid Topography Research Model) with subgrid corrections to compute compound flooding in coastal systems resulting from fluvial, pluvial, tidal, and wind-driven processes. A key contribution is the model’s ability to enforce all flood drivers and use the subgrid corrections to improve the accuracy of the coarse-resolution simulation. The model is validated for Hurricane Eta 2020 in Tampa Bay, showing improved prediction accuracy with subgrid corrections at 42 locations. Subgrid models with coarse resolutions (R2 = 0.70, 0.73, 0.77 for 3-, 1.5-, 0.75-km grids) outperform standard counterparts (R2 = 0.03, 0.14, 0.26). A 3-km subgrid simulation runs roughly 50 times faster than a 0.75-km subgrid simulation, with similar accuracy. 

Sediment cores from blue holes have emerged as a promising tool for extending the record of long‐term tropical cyclone (TC) activity. However, interpreting this archive is challenging because storm surge depends on many parameters including TC intensity, track, and size. In this study, we use climatological‐hydrodynamic modeling to interpret paleohurricane sediment records between 1851 and 2016 and assess the storm surge risk for Long Island in The Bahamas. As the historical TC data from 1988 to 2016 is too limited to estimate the surge risk for this area, we use historical event attribution in paleorecords paired with synthetic storm modeling to estimate TC parameters that are often lacking in earlier historical records (i.e., the radius of maximum wind for storms before 1988). We then reconstruct storm surges at the sediment site for a longer time period of 1851–2016 (the extent of hurricane Best Track records). The reconstructed surges are used to verify and bias‐correct the climatological‐hydrodynamic modeling results. The analysis reveals a significant risk for Long Island in The Bahamas, with an estimated 500‐year stormtide of around 1.63 ± 0.26 m, slightly exceeding the largest recorded level at site between 1988 and 2015. Finally, we apply the bias‐corrected climatological‐hydrodynamic modeling to quantify the surge risk under two carbon emission scenarios. Due to sea level rise and TC climatology change, the 500‐year stormtide would become 2.69 ± 0.50 and 3.29 ± 0.82 m for SSP2‐4.5 and SSP5‐8.5, respectively by the end of the 21st century.