Observational Analysis And Numerical Study Of The Influence Of Kuroshio Over The East China Sea On The Intensity Of Tropical Cyclone

Based on the AVHRR high-resolution sea surface temperatures and tropical cyclone (TC) dataset of Japan Meteorological Agency for the period of1982to2008, statistic analyses are firstly performed to study the effects of Kuroshio over the East China Sea on TCs in summer. Then, its possible mechanisms were studied by using the method of mesoscale numerical model,The main conclusions are as follows:(1) Statistics indicated that there are27TCs,which accouts for30%of the total number of TCs passing the warm tongue of Kuroshio during the27years in the summer,are strengthened. The track of TCs are in the direction from Northeast to Southwest on June and July, same as the orientation of the warm tongue. Then, six rapidly intensified TCs are selected to study the mechanisms by which the Kuroshio enhances TCs, based on composite analysis, and results indicate that the increasing heat fluxes along the warm tongue of Kuroshio play an important role in strengthening these TCs’ intensity.(2) A mesoscale numerical model (WRF) is used to study the effect of Kuroshio on TC Noguri in2002-a typical intensified case. The WRF model well reproduces the Noguri’s rapidly intensified process when it passes the Kuroshio warm tongue. Another two sensitivity experiments are designed to further explore the influence of the warm tongue on TC’s intensity with different SSTs. Different SSTs significantly change the intensity of Noguri, but little change the track. Numerical results show that the enhanced effect by the warm Kuroshio is much larger than the weakened effect by cold water due to TC-induced upwelling. As a result, the warm tongue of Kuroshio acts to excite cumulus convection and then enhance TC’s intensity through increasing sea surface heat fluxes(3) A weaken TC Ewiniar which passed the key region of Kuroshio in2006is taken as an example to study the influence of Kuroshio on the weaken TCs. The track and weaken process of Ewiniar is reproduced by the WRF model. We designed four sensitivity experiments to investigate the impacts of different SSTs on Ewiniar’s intensity. Comparing the control experiment with the three groups of constant SST experiment, we find that the weaken effect by cold water due to TC-induced upwelling is much larger than the enhanced effect by the warm Kuroshio. The difference between control and smoothed SST runs indicate that the warm tongue of Kuroshio also acts to excite cumulus convection and then restrain TC’s weaken process through increasing sea surface heat fluxes.