超强台风“威马逊”登陆前快速加强的特征和原因分析

Analysis of the Characteristics of Rapid Intensification of Super Typhoon Rammasun and Their Causes

利用NCEP资料、CMA-STI热带气旋最佳路径数据和FY系列卫星云图对超强台风"威马逊"登陆前特征和突增成因进行分析。结果表明:"威马逊"强度突增期间副高西伸脊点显著东退,高低压之间维持强的气压梯度。台风急剧发展期间结构趋于对称化加强,高低层辐合辐散急剧发展,持续增强的正涡度柱不断向平流层上层发展,同时垂直速度不断增大从低层向上传播,这些结构都利于台风强度迅速增强。环境条件分析表明西太平洋高海温、弱的环境风垂直切变维持10 m/s以下速度,有利于凝结潜热聚集和台风"暖心"结构维持;850 h Pa上偏南气流显著增强,南侧水汽通道完全接通且水汽辐合与台风中心基本重合,促使水汽向台风中心辐合输入,是"威马逊"强度剧增的重要原因之一。

Utilizing NCEP global assimilation analysis data,location data of tropical cyclones and FY satellite images,we analyzed the strength characteristics and causation of its intensification before the landing of Super TY Rammasun. Conclusions indicate that a subtropical high in Western Pacific（ SHWP for short） strengthened and moved westward during the early phases of typhoon ＇s development,but obviously eastward during the process of rapid intensification,which caused high pressure gradients between Super TY and SHWP. During the rapid intensification,symmetric structure,favorable background field with low- level convergence and high- level divergence,positive vorticity increasing in the eye of the typhoon and expanding to the mid and upper- troposphere,and vertical velocity increasing upward are the main reasons of the intensification of Rammasun. Analysis on the environment condition shows that high sea temperature and weak vertical wind shear lower than 10 m / s were in favor of gathering the latent heat of condensation and maintaining the ＂warm core＂structure. Eventually,a noteworthy strengthening of southerly airflow over the northeast typhoon side,a southern water vapor channel fully connected to the typhoon circulation as well as the vapor convergence essentially coincident with the typhoon center are the most significant factors contributing to the intensification of Rammasun.