Impact of Precipitation on Ocean Responses during Tropical Cyclone

Abstract

Precipitation plays a crucial role in modulating upper ocean salinity and the formation of barrier layer, which affects the development of tropical cyclones (TCs). This study performed idealized simulations to investigate the influence of precipitation on the upper ocean. Precipitation acts to suppress the wind-induced sea surface reduction and generates an asymmetric warming response with a rightward-bias. There is substantial vertical change with a cooling anomaly in the subsurface, which is about three times larger than the surface warming. The mean tropical cyclone heat potential is locally increased but the net effect across the cyclone footprint is small. The impact of precipitation on the ocean tends to saturate for extreme precipitation, suggesting a non-linear feedback. A prevailing driver of the model behavior is that the freshwater flux from precipitation strengthens the stratification and increases current shear in the upper ocean, trapping more kinetic energy in the surface layer and subsequently weakening near-inertial waves in the deep ocean. This study highlights the competing role of TC precipitation and wind. For TC is weaker than Category 3, the warming anomaly is caused by reduced vertical mixing, whereas for stronger TCs, the advection process is most important.