0608号超强台风“桑美”强度变化位涡诊断分析

A Potential Vorticity Diagnosis Analysis on the Intensity Evolution of 0608 Super Strong Typhoon "Saomai"

利用位涡(PV)收支诊断和质点轨迹追踪等方法对2006年影响中国最严重的超强台风"桑美"强度变化的成因进行了分析和研究。结果表明:台风中心四周的垂直风切变、涡度、散度变化对台风强度变化有重要影响;通过位涡诊断揭示出在台风增强和减弱时,凝结潜热、垂直平流和水平平流起着不同的作用。在台风迅速发展之前和迅速发展初期,凝结潜热在对流层低层起主要作用;在台风迅速发展阶段,水平平流在整个对流层都起主要作用;在台风迅速减弱阶段,垂直平流在底层发挥着重要作用,促使台风底层的位涡迅速减小。拉格朗日回推轨迹追踪分析表明在台风强度变化过程中,高层东南侧气流的介入和低层南侧气流的流入对桑美台风的发展有重要贡献。

Based on Potential Vorticity（PV） budget diagnosis and particle track and so on,the causes of intensity evolution of super strong typhoon ＂Saomai＂ which impacted China most severely in 2006 is analyzed and studied.The results show that the variations in the vertical wind shear,vorticity and divergence around the center of the typhoon significantly effected the variation in its intensity.The PV dignosis shows the functions of latent heat of condensation,vertical advection and horizonal advection were different while the typhoon intensified and abated.Condensation latent heat plays a dominant role in the lower troposphere at early rapid development stage and before development,so does horizontal advection in the whole troposphere at the rapidly developing stage,and verticl advection in the bottom layer of typhoon at rapidly weakening stage which reduces the potential vorticity,respectively.Lagrangian backward trajectories revealed that the instrusions of air from the southeast at upper level and from the south at lower level contributed a lot to the development of Saomai while the typhoon′s intensity was changing.