Impacts of Air–Sea Interaction on Tropical Cyclone Track and Intensity

While the previous studies of the impacts of air–sea interaction on tropical cyclones (TCs) generally agree on significant reduction in intensity and little change in track, they did not further explore the relative roles of the weak symmetric and strong asymmetric sea surface temperature (SST) anomalies relative to the TC center. These issues are investigated numerically with a coupled hurricane–ocean model in this study. Despite the relatively small magnitude compared to the asymmetric component of the resulting cooling, the symmetric cooling plays a decisive role in weakening TC intensity. A likely reason is that the symmetric cooling directly reduces the TC intensity, while the asymmetric cooling affects the intensity through the resulting TC asymmetries, which are mainly confined to the lower boundary and much weaker than those resulting from large-scale environmental influences. The differences in TC tracks between the coupled and fixed SST experiments are generally small because of the competing processes associated with the changes in TC asymmetries and the beta drift induced by air–sea interaction. The symmetric component of the SST drop weakens the TC intensity and outer strength, leading to a more northward beta drift. On the other hand, since the asymmetric component of the SST cooling is negative in the rear and positive in the front of a TC in the coupled experiments, the enhanced diabatic heating is on the southern side of a westward-moving TC, tending to shift the TC southward. In the coupled model the westward TCs with relatively weak (strong) outer strength tend to turn to the north (south) of the corresponding TCs without air–sea interaction. 1