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The Effects of Explicit Wind-Wave-Current Coupling on Hurricane Structure and Coastal Impacts

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Abstract

The most significant hurricane impacts experienced by coastal communities are flooding and extreme winds. These flooding events are due to the compound effects of extreme rainfall, large surface waves and storm surges at the coast. A key process influencing the surface winds, waves and storm surges is the complex momentum exchange at the air-sea interface. This study focuses on better understanding and modeling of hurricane rain, winds, surface waves, ocean currents, and storm surges that are critical for response to impacts from landfalling hurricanes. We used a high-resolution (~1 to 4 km) coupled atmosphere-wave-ocean model, namely the Unified Wave INterface - Coupled Model (UWIN-CM) to simulate both Hurricane Earl (2010) and Irene (2011). For each storm, we compared a fully coupled atmosphere-wave-ocean model with explicit momentum exchange, separating the atmospheric and ocean stresses (full physics) with a model experiment with no separation (simple physics). In the case of Hurricane Earl we found that explicit air-sea momentum exchange 1) improves surface wave growth and propagation ahead of the storm, which can impact the coastal zone while hurricanes are over the open ocean, 2) increases the size of the hurricane with respect to surface winds, and 3) reduces hurricane-induced upper ocean cooling by improving ocean currents and mixing. For Hurricane Irene, our results revealed that explicit air-sea momentum exchange 1) improved storm surge forecast through better prediction of waves and wave dissipation in the coastal zones and 2) increased accumulated rainfall by up to 30%. These results show that explicit wind-wave-current coupling is critical for coastal impacts, which requires correct air-sea momentum exchange for hurricanes over the open ocean and at landfall. This study has an important implication for future offshore wind-wave energy infrastructure over the East Coast of the US and the Caribbean Islands.

Category
Coastal
Extremes Events
Energy, Water, and Land System Transition
Funding Program Area(s)