冷空气入侵对0509号台风“麦莎”变性的作用

利用地面和高空的实况观测资料、NCEP／NCAR再分析资料以及FY-2C卫星云图资料，并通过中尺度Barnes滤波和物理量诊断分析，对台风“麦莎”变性过程进行研究。采用非静力平衡的中尺度模式MM5（V3．7）对“麦莎”北上变性，影响京津地区降水的全过程进行了60h模拟。结果表明：“麦莎”登陆北上过程中，西北侧冷空气先随着“麦莎”环流由北向南旋转，尔后冷空气又从台风低压中心的偏南侧向北侵入，逐步侵入“麦莎”暖心结构；在垂直方向上，对流层中高层不断有系统性的冷空气倾斜向下补充，冷空气从对流层低层侵入台风环流，最终使“麦莎”变性。在接近华北地区时，“麦莎”云系发生分裂，偏西侧云系的出现和发展与低层850hPa流场上中尺度辐合线的产生密切相关，其中冷空气的作用显著。

Impacts of Cold Air Intrusion on Extratropical Transition of Typhoon Matsa

Using the radiosonde and surface observation data, NCEP/NCAR reanalysis data and FY-2C satellite cloud images, the extratropical transition of typhoon Matsa is analyzed by means of mesoscale Barnes filtering and physical variable diagnosis. The evolution of Matsa after landfall and the process of Tianjin and Beijing＇s precipitation are simulated for 60 h by the Penn State NCAR nonhydrostatic mesoscale model（ MM5 ）. The results show that during the landfalling ing and northward going process of Matsa, the cold air in its northwest side first rotated along the typhoon circulation from the north to the south, and then intruded northward from the south into the warm center of Matsa gradually, and at the same time in the vertical direction there were cold airs systematically/slanfly descending from the middle-upper troposphere and intruding into the typhoon circumfluence at the low level, which at last resulted in the extratropical transition of Mstsa. The cloud system of Matsa split into the west part and east one, when Matsa appoached to North China, and the emergence and development of the westside cloud is close connected with the genesis of the mesoscale convergence line at 850 hPa stream field,in which the clod air took part important role.