Impact of Rainfall on Tropical Cyclone-Induced Sea Surface Cooling

Karthik Balaguru, Gregory R. Foltz, L. Ruby Leung, Samson M. Hagos


Department of Energy, Office of Science, Earth & Environmental Systems Modeling Progam Acknowledged Support: Yes, Regional and Global Modeling Analysis Program


Tropical cyclones (TCs) are often accompanied by strong winds and torrential rains. While the winds associated with TCs tend to enhance mixing in the upper ocean, the freshwater input from rain can stratify the water column and limit mixing. However, the extent to which the stabilizing effect of rainfall can compete with wind-induced mixing and to what degree it modulates TC-induced sea surface cooling remain unknown. Here we show, using a suite of observations, that heavy rains under weak TCs can significantly reduce the magnitude of cold wakes induced by them. When compared to storms with low rain rates, the ocean surface under TCs with high rain rates freshens significantly and cools less. High-resolution climate model simulations and idealized experiments with an ocean mixed layer model support these results and reveal that oceanic mixing processes are primarily responsible for reduced cooling under TCs, with a lesser role for surface fluxes.

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