Tropical cyclones (TC) are one of the most significant disasters due to their damaging impact on human life and infrastructure through storm surge, torrential rain, flooding, and severe winds. The economic damages associated with TCs may substantially increase in the future due to projected global warming. One challenge is that future TC projections with atmosphere-only models are associated with uncertainties due to their inability to represent TC-ocean interactions. However, global coupled models, which represent TC-ocean interactions, can produce basin-scale sea surface temperature biases in seasonal to centennial simulations that lead to challenges in representing TC activity. Therefore, focusing on recent individual major events, we investigated the influence of TC-ocean coupling on the response of TCs to anthropogenic change by comparing atmosphere-only (WRF) and coupled atmosphere-ocean (WRF coupled to ROMS) regional model simulations. The simulations include hindcasts of the TC events in the historical climate in which they occurred and experiments representing the TCs in a future warmer climate (SSP5-8.5) using the pseudo global warming method. We focused on TC rainfall and intensity and their associated storm surge hazards in the North Atlantic region.
Under an extremely warm scenario, atmosphere-ocean coupling does not influence the signs of projected TC rainfall and intensity responses. Atmosphere-ocean coupling, however, does influence the magnitude of projected intensity and especially rainfall. Within a 500 km radius region of the TCs, the projected rainfall increases in coupled simulations are 3-47% less than in the atmosphere-only simulations, likely because of the enhanced TC-induced sea surface temperature cooling in the former. However, due to the heterogeneous nature of rainfall, the influence of atmosphere-ocean coupling on the magnitude of projected rainfall could vary considerably over the regions of the highest rainfall generated by TCs.
The simulated TC wind and pressure fields are then used to force the ADCIRC storm surge model. Preliminary results show that the storm surge caused by several recent major hurricanes would increase by more than a factor of three in the future warmer climate, due to increased TC size and intensity. For the TCs considered, the storm surge tends to be greatest to the east of the TC landfall location, both in the historical and future warmer conditions. Although the landfall location, and thus the location of the maximum storm surge, may shift considerably in warmer conditions, we found that the storm surge at the historical landfall location was considerably higher in the warmer conditions, potentially due to the larger wind field and size of TCs. Further assessment revealed that simulated storm surge was higher when using atmosphere-only meteorological forcing compared to coupled atmosphere-ocean meteorological forcing for all of the TCs considered in this study. Our findings highlight some important differences in projected TC statistics and associated hazards between atmosphere-only and coupled atmosphere-ocean model simulations.