Both of Typhoon Winnie (9711) and Matsa (0509) underwent an extratropical transition (ET)
process when they moved northward after landfall and affected Liaodong Peninsula. However, Matsa
produced half as much rainfall as Winnie, although it struck Liaodong Peninsula directly while Winnie
passed through the Bohai Sea. The relations between the ET processes and the precipitation over Liaodong
Peninsula are examined. The result shows that the precipitation difference between Winnie and Matsa was
closely related to the interactions between the westerly systems and typhoons during their ET processes.
Winnie was captured by the upper westerly trough and then coupled with it when moving to the
mid-latitudes, and the positive anomaly of moist potential vorticity (MPV) was transported downward from
the upper troposphere over the remnant circulation of the tropical cyclone (TC). It was favorable to the
interaction between tropical warm and wet air and westerly cold air, causing convective cloud clusters to
form and develop. The rain belt composed of several meso-β cloud clusters over the Liaodong Peninsula,
resulting in heavy rainfall. On the other hand, Matsa did not couple with any upper trough during its ET
process and the positive anomaly of MPV in the upper troposphere and its downward transfer were weak.
Only one meso-β cloud cluster occurred in Matsa’s rain belt during its ET process that tended to lessen
rainfall over Liaodong Peninsula. 相似文献