1713号台风“天鸽”近海突变特征及原因分析

Analysis on the sudden change and its cause of Typhoon Hato

使用NCAR/NCEP再分析资料和国家气象中心提供的逐时热带气旋资料,分析了台风"天鸽"的路径和强度特征,并在此基础上分析其近海突变原因,结果表明:(1)22日15时—23日13时为"天鸽"突变的关键时间段,突变第一段为22日15时—23日00时,第二段则为23日09—13时;(2)高海温对"天鸽"的加热作用导致了"天鸽"的近海突变;(3)"天鸽"的两次突变增强后,都伴随有更充沛的水汽输送,这有利于"天鸽"的潜热释放作用增强,进而引起"天鸽"强度突然增大。"天鸽"两次强度突变前,伴随着风垂直切变迅速减小,而突变后,高层出流的突然增大带来风垂直切变的增大;(4)涡度场演变特征与"天鸽"强度突变有着较好的对应关系,其中辐散项引起的低层辐合增强,有利于高层辐散气流的发展,而高层辐散的增强同时又有利于中低层辐合的进一步发展。这种正反馈机制促进了低层正涡度和高层负涡度的积累,引起了台风"天鸽"的强度突变。

Based on the NCAR/NCEP reanalysis data and the hourly tropical cyclone data provided by National Meteorological Center of China Meteorological Administration, the track and intensity characteristics of Typhoon Hato and the reasons of its rapid intensification over inshore coastal water are analyzed in this study. Results indicate that：（1）The period from 15：00 on 22 to 13：00 on 23 August are the key time periods of Hato＇s rapid intensification. During this period, Hato intensified from tropical storm to strong tropical storm and then further to strong typhoon. Its rapid intensification can be divided into two phases in which the first covering from 15：00 on 22 to 00：00 on 23 August and the second from 9：00 to 13：00 on 23.（2）The influence of warm SST on Hato was revealed by its sudden intensity change over coastal water.（3）The two phases of rapid intensification were coincided with more abundant water vapor transport which is in favor of the strengthen of Hato＇s latent heating release and rapid intensification. Furthermore, the vertical wind shear swiftly decreased and increased before and after the sudden change of Hato＇s intensity in which the latter process is caused by the strengthening of upper-layer outflows.（4）The evolution of vorticity was in close relationship to the rapid intensification of Hato,while the lower-level convergence caused by the convergence term enhanced and led to the development of upper-layer divergence flows which further promoted the increase of mid-and lower-level convergence. The positive feedback brought about the accumulation of lower-layer positive vorticity and upper-layer negative vorticity and then led to the sudden intensifying of Hato.