Abstract
Tropical cyclones (TCs) can affect the thermal structure in the upper ocean by mixing. In turn, upper-ocean thermal structure also affects the evolution of TCs. Here based on satellite data, in situ temperature and salinity observations and the best-track data of the U.S. Joint Typhoon Warning Center, combined with an ocean mixed layer model, the role of the pre-existing summer upwelling of the northern South China Sea (NSCS) in TCs self-induced sea surface cooling was explored. The modeling results showed that for a given atmospheric thermodynamic condition, TCs self-induced sea surface cooling is quite different when they pass over the regions with pre-existing upwelling and without upwelling. The amplitude of TCs self-induced cooling is larger by more than 50% in the region with pre-existing upwelling than that without. For example, for a slow-moving typhoon with translation speed of 4 m/s and wind speed of 45 m/s, TC self-induced surface cooling is 2.5°C when they pass over the upwelling region, but only 1.5°C when they pass over the region without upwelling. The results suggest that upwelling of the NSCS could amplify TCs self-induced cooling and play a negative role in TCs intensification before they made landfall in Southern China.
Highlights
IntroductionAs one of the most important physical processes linking to wind-driven currents and shelf topography in the marginal ocean, is commonly
For a slow-moving typhoon with translation speed of 4 m/s and wind speed of 45 m/s, Tropical cyclones (TCs) self-induced surface cooling is 2.5 ̊C when they pass over the upwelling region, but only 1.5 ̊C when they pass over the region without upwelling
The results suggest that upwelling of the northern South China Sea (NSCS) could amplify TCs self-induced cooling and play a negative role in TCs intensification before they made landfall in Southern China
Summary
As one of the most important physical processes linking to wind-driven currents and shelf topography in the marginal ocean, is commonly. Evidences from numerous studies indicate that typhoon-induced strong vertical ocean mixing can bring deep cold water to the surface, and make sea surface temperature (SST) cooler than the ambient waters by up to 2 ̊C to 6 ̊C [16] [17] [18] [19]. Leipper [21] and Shay, Goni and Black [17] reveal that the presence of ocean cold or warm features could impact TC-induced SST cooling and the intensification of TCs. In warm ocean, e.g. warm boundary currents or warm eddies, ocean upper mixed layers are deep and the associated ocean heat contents relative to the 26 ̊C isotherm often exceed 100 kJ/cm, which. Few studies have been made to investigate the role of the pre-existing summer upwelling of NSCS in TCs self-induced SST cooling.
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