Air-Sea Coupling Influence on Projected Changes in Major Atlantic Hurricane Events
Tropical cyclone (TC)-ocean coupling is necessary to represent the processes important for TC intensity. However, typical biases in global coupled models can cause substantial errors in simulated TC activity. We investigated how the treatment of the ocean (coupled or prescribed sea-surface temperatures) influences future projections of Atlantic TCs using regional model simulations. We performed ensembles of atmosphere-only and atmosphere-ocean simulations of five historically impactful Atlantic hurricane events in historical and future climates.
We found that regardless of the treatment of the ocean, TC intensity, precipitation, and size are projected to increase in the future. Projections of future TC precipitation increases are weaker in the coupled simulations than in the atmosphere-only simulations by 3-59%.
Tropical cyclone (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 major hurricane events, we investigated the influence of TC-ocean coupling on the response of TCs to anthropogenic climate change using atmosphere-only and coupled atmosphere-ocean regional model simulations. Under a high greenhouse gas emissions scenario, coupling does not influence the signs of projected TC precipitation and intensity responses. Coupling, however, does influence the magnitude of projected TC intensity and especially precipitation. Within a 500 km radius around the TCs, the projected precipitation increases in coupled simulations are 3–59% less than in the atmosphere-only simulations, driven by enhanced TC-induced sea surface-temperature cooling in the former.