Influence of Vertical Wind Shear on the Ocean Response to Tropical Cyclones Based on Satellite Observations

We here investigate the effects of tropical cyclone (TC)-induced rainfall asymmetries driven by vertical wind shear on ocean salinity and temperature response to TCs using satellite and in situ observations. On average, TCs tend to initially freshen the ocean surface due to heavy rainfall and subsequently salinity from upwelling and vertical mixing, with strongest surface salinification on the right-hand side of the Northern Hemisphere TCs. The direction of shear has been found to control the location of maximum TC rainfall, resulting in more freshwater accumulation on the right-hand side of the right-sheared storms. The accumulated freshwater strengthens salinity stratification and inhibits right-side biased vertical mixing, reducing subsequent surface salinification by 0.15-0.3 psu and slightly suppressing the surface cooling by about 0.15 degrees C, relative to left-sheared storms. Thus, the directionality of shear can impact ocean-TC coupling. Plain Language Summary The cooling of the ocean surface by tropical cyclones (TCs) can influence the evolution of TC intensity and is driven by vertical exchanges in the ocean, which tend to be strongest on the right-hand side of the Northern Hemisphere TCs. TC-induced changes in salinity can influence upper ocean stability, a key influence on ocean dynamics. In this study, we investigate the influence of environmental vertical wind shear direction on TC-induced rainfall asymmetries, and their subsequent impacts on the ocean salinity and temperature response to TCs with satellite observations and Argo profiles. Here we show that more freshwater is accumulated on the right-hand side when the vertical wind shear direction is towards the right of storm motion in the Northern Hemisphere, which reduces the TC-induced surface salinity increase and causes weaker vertical mixing on the right-hand side of the storm. Since the vertical mixing is strongest on the right-hand side of the Northern Hemisphere storms, more freshwater on the right-hand side also results in muted surface cooling. Key Points Vertical wind shear impacts the ocean response to tropical cyclones through affecting the tropical cyclone rainfall distribution More freshwater to the right of the right-sheared storms increases salinity gradient and inhibits mixing, reducing surface salinification The restrained mixing on the right-hand side slightly suppresses the surface cooling and chlorophyll-a enhancement