Abstract
The effects of changes to the surface on the Tropical Cyclone (TC) intensity and wind structure is detailed. First, idealized simulations of TCs over ocean waters featuring sub-surface oceanic barrier layers (OBLs) reveal that for TCs of category 1 hurricane strength or greater, thick (24–30 m) OBLs favor further intensification by 10% on average. Conversely, weaker cyclones are hindered by thick OBLs. Reduced sea surface temperature cooling below the TC inner core is the primary pathway for additional intensification. Sensitivity tests of the results to storm translation speed, initial oceanic mixed layer temperature, and atmospheric vertical wind shear provide a more comprehensive analysis. Next, the sensitivity of the near-surface wind decay within landfalling idealized TCs to inland surface aerodynamic roughness lengths and soil moisture content was evaluated. Results show that the wind field decay is initially sensitive to the surface roughness within 12 h of landfall and beyond, and an increasing sensitivity to soil moisture contents farther inland after significant weakening and TC size expansion has occurred. Additionally, surface roughness has a greater effect on the most intense winds, while soil moisture has a stronger control on the weaker, outer core winds. Finally, the evolution of the TC boundary layer wind field before and during landfall is detailed through analysis of idealized simulations. Wind speed and direction data collected by offshore buoys and coastal stations during the landfalls of four Gulf of Mexico hurricanes are compared with the idealized simulations. In addition, the development of internal boundary layers downstream from the coast is discussed, and heights of the layer are compared to theoretical heights.