The Role of the WISHE Mechanism in Rapid Intensification of Tropical Cyclones

During the past few decades, the improvement in intensity forecasts has been relatively slow. The rapid intensification (RI) of TCs is one of the important process which can affect the TC intensity evolution and bring challenge to TC intensity prediction. Results from the previous numerical or observational studies showed that the swirling wind fields of TC usually expand or intensify during RI. The wind-induced surface heat exchange (WISHE) mechanism can be bring out since the mechanism describes the positive feedback between the surface wind speed and the surface energy flux. Therefore, based on the previous studies and the physical concepts, how the increasing surface wind and heat fluxes at the air-sea interface affects the RI is examined in this study.

Comparing with the control experiment, the sensitivity experiments with capped WISHE mechanism show delayed RI, and leads to weaker peak intensity. Interestingly, the WISHE-capped experiments reach the criteria of RI via the increase of the maximum surface wind speed (intensify more than 30 kts in one day), but cannot achieve the criteria of the deepening of the minimum sea level pressure (deepens more than 42 hPa during one day). The potential temperature budget and the tangential wind budget are adopted to evaluate the intensifying processes of RI. Furthermore, the WISHE mechanism can affect the thermodynamic environment and the convective-scale processes, for instance, the establishment of the warm core, the distribution of the vertical velocity, and the increase of the inertial stability in the inner core area. These above results have pointed out the crucial role of the WISHE feedback in RI. Further examinations of these issues will be carried out in this study.