0421号热带风暴“海马”登陆后的温带变性过程特征探讨

Exploration for characteristics of extratropical tramsformation course of landing tropical storm No.0421(Haima)

0421号热带风暴“海马”于2004年9月13日12:00在浙江温州市沿海登陆后,迅速减弱为热低压,然后继续北移;并在中高纬高空槽后的冷平流和中低纬低层暖式切变南部的暖平流共同作用下,低压加深及冷、暖锋生,发展为斜压温带锋面气旋.采用相对辐散作为气旋发展的判据,能很好地体现整个变化过程,气旋的移向基本上沿着相对辐散中心长轴方向移动.通过对地面温度场水平结构分析后发现,该气旋经历了3个阶段:暖涡旋基本对称结构、半冷半热非对称结构、冷涡旋基本对称结构.对流层低层气旋中心上空为暖平流区,引导气旋移动,而对流层中层的冷平流中心区一直位于气旋移向的下侧,推动气旋移动.

After landing at 12:00,Sep.13,2004,the tropical storm of 0421 is rapidly weaken to be a hot low pressure and then moves to the north continuously.Under the coaction of the cold advection behind the high-level trough over the middle-high latitude area and the warm advection on the south of warm shear over the middle-low latitude area, the low pressure is deepened and the cool and warm fronts are born. The baroclinic frontal cyclone on temperate zone has developed. The relative divergence is adopted as the judging evidence of the cyclone development, and can reflect the entire alternation process well. The cyclone moves basically along the long-axis orientation of the relative divergence center.It shows from the horizontal structural long-axis analysis of surface of temperature field that the cyclone goes through three stages: the basic symmetric struture of warm vortex, the non-symmetric structure of half cold and half hot and the basic symmetric structure of cold vortex. The warm advection area locates over the cyclone center in the lower layer of the troposphere.It steers the cyclone to move.And the cold advection center area in the middle layer of the troposphere locates on the doown side of the cyclone path continuously.It promotes the cyclone to move.