利用日本气象厅区域谱模式（RSM）20 km再分析资料及改进的调和—余弦算法，对2006年4号台风Bilis登陆后暴雨增幅前后风场的结构变化特征进行了比较分析。Bilis台风登陆西行过程中，于14日18：00（协调世界 时，下同）开始，至15日12：00出现明显的暴雨增幅现象。在暴雨增幅前后时段，暴雨区的全风场及无辐散风分布变化强度小于无旋风。具体表现为：暴雨增幅前，Bilis低层西南部的无旋风速加强，辐合中心与Bilis中心逐步靠近，垂直上升运动加强；在暴雨增幅期间，Bilis西南部的低层和高层的无旋风速都一致持续加强。这种无旋风场上的变化与暴雨强度变化有很好的相关性，即：无旋风在Bilis西南部的增强及辐合增强与该区域暴雨的增强相对应，暴雨增幅的时段与高低层无旋风的风速加大和辐合增强是一致的。对暴雨增幅起主导作用的是无旋风的变化及其引起的散度变化。无旋风速及辐合增强时，暴雨增强并维持；无旋风及辐合减弱后，暴雨强度逐渐减弱。无辐散风强度变化与暴雨强度变化相反，而全风速在暴雨增幅前主要由无旋风决定，暴雨减弱阶段主要由无辐散风决定，对无旋风及无辐散风的分析能更加明显的揭示出暴雨增幅时期风场的具体变化。相对于全风场分析，无辐散风和无旋风能提供更多的风场结构变化与暴雨增幅的关系，这对于预报和分析登陆台风的风雨分布有一定的促进作用。
By using the regional spectrum model reanalysis data from the Japan Meteorological Agency with a horizontal resolution of 20 km and a time interval of 6 h, in addition to nondivergent and irrotational wind components derived through harmonic-cosine spectrum expansion, wind structure features were compared prior to and following the rainstorm amplification of typhoon Bilis (0604). After Bilis landed on the Chinese mainland, the rain amplification was noticeable on its southeast quadrant, particularly from 18 UTC July 14 to 12 UTC July 15, 2006. The analysis results show that the variation amplification of the entire wind speed and the nondivergent wind component were less than that of the irrotational wind component. In detail, before the rainstorm amplification occurred, the irrotational wind component of the southeast quadrant increased on the lower and upper levels, and the distance between convergence center and the center of Bilis narrowed. Thus, the vertical upward motion strengthened. During the period of rain amount amplification, the irrotational wind of the lower and upper levels increased as well. Therefore, the variation of irrotational wind is relevant to the variation in rainfall intensity. The variation of irrotational wind and its resultant divergence were the main factors for the rainfall amplification. The enhancement/diminishing of irrotational wind and divergence were always accompanied by an increase/decrease in rainfall amount. The tendency of nondivergent wind was opposite that of the rainfall amount, and although the whole wind speed was determined mainly by the irrotational wind during the rainfall amplification, it was affected more by the nondivergent wind during the rainfall weakening process. The analysis for the irrotational and nondivergent winds can indicate additional wind variation characteristics. The conventional analysis method for the entire wind cannot reveal the changes of irrotational and nondivergent winds and their relative importance when rainfall occurred. From the wind decomposition results, we conclude that before and after the rainstorm amplification of Bilis, the change in wind field was reflected mainly on the irrotational component, which was sensitive to the change in rainfall. Thus, this method is effective for predicting wind and rainfall distribution for the landed typhoons.
周玉淑,邓涤菲,李建通.登陆热带气旋Bilis（0604）暴雨增幅与风场结构变化.大气科学,2014,38(3):563~576 ZHOU Yushu, DENG Difei, LI Jiantong. Rainstorm Amplification of Typhoon Bilis (0604) and Its Wind Structural Change. Chinese Journal of Atmospheric Sciences (in Chinese),2014,38(3):563~576复制