变性台风“美莎克”结构演变特征及暴雨成因分析

Structural evolution characteristics and cause analysis of heavy rain of transition typhoon"Maysak"

台风“美莎克”(2009)在菲律宾以东洋面上生成后沿我国近海北上并不断加强,最强达到超强台风,登陆后在我国东北地区一路西行,与冷涡结合逐渐变性加强,移动缓慢,给东北地区中北部带来大范围持续暴雨天气。使用常规观测资料、FY-2F云顶亮温资料及NCEP FNL再分析资料,对台风“美莎克”在中高纬西行深入内陆与冷涡结合变性加强的过程进行了分析。结果表明:(1)有利的高低空动力条件配置及水汽的相变驱动作用导致台风的不对称发展,在垂直方向上呈现向西倾斜的结构。主体云系和强降水主要出现在顺切变方向的左侧。(2)台风暴雨以稳定性降水为主,只在降水开始之初有对流活动造成短时强降水。锋面低层的中尺度强锋生区对暴雨有较好的指示意义。(3)台风北上携带的水汽充沛,东南部大暴雨区中低层比湿大,强降水时段集中、降水强度大;暖锋锋生、中层对流不稳定和湿对称不稳定,有利于强降水的维持和发展。台风深入内陆的过程中变性发展,移动缓慢,降水持续时间长,以锋面和气旋稳定降水为主。(4)东南部大暴雨区位于长白山脉北侧,偏东风低空急流与地形正交,大暴雨带的走向与地形走向一致,迎风坡地形对降水有增幅作用。

Typhoon"Maysak"(2009)was formed of the East ocean in the Philippines,then moved north along the coastal waters of China and continued to strengthen,reaching a super typhoon at its strongest.After landfall,the typhoon moved westward in the Northeast of China.The combination of the typhoon and the cold vortex gradually strengthened and moved slowly,bringing a large range of continuous heavy rain to the central and northern parts of the northeast.Based on FY-2F infrared brightness temperature data,the conventional observational data and NCEP FNL reanalysis data,the weather process of typhoon"Maysak"degeneration intensification due to its combination with cold vor⁃texes when it went deep inland in mid-high latitude westbound was analyzed.The major conclusions are as follow:(1)the favorable high and low air dynamic condition configuration and the phase change driving action of water vapor led to the asymmetric development of typhoon,which presented a west-inclined structure in the vertical direction.The main cloud system and heavy precipitation mainly appeared on the left side along the shear direction.(2)Typhoon rainstorms were dominated by stable precipitation,and only the short-time heavy precipita⁃tion caused by convective activity appears at the beginning of the precipitation.The mesoscale strong frontal zone in the lower layer of the front was a good indicator of the rainstorm.(3)Typhoon carried abundant water vapor northward,and the specific humidity in the middle and lower layers of the southeast heavy rain region was larger.The heavy precipitation was concentrated in the period of time and the precipitation intensi⁃ty was high.The convective instability and wet symmetry instability in the middle layer of the warm front are conducive to the maintenance and development of heavy precipitation in the southeast heavy rain region.During the process of typhoon goingdeepintotheinland,itdevelopedvar⁃iously,moved slowly,and the precipitation lasted for a long time,which was dominated by the stable precipitation of front and cyclone.(4)The rainstorm zone in the southeast was located on the north side of the Changbai Mountains.The easterly low level jet was orthogonal to the topogra⁃phy,and the windward slope topography increased the precipitation.The trend of the rainstorm zone was consistent with the topography.