台风“麦莎”两次东折成因的诊断分析

The Diagnostic Analysis Of Track Turning Eastward Cause Of Typhoon Matsa

利用1°×1°NCEP再分析资料,主要从副高面积指数、麦莎的移速与台风移向的关系、风场、变高场以及高空辐散场等方面对台风"麦莎"的两次东折作了分析。发现:两次东折时,副高面积指数处在增加中;两次东折前,麦莎移速一直在减小,但是东折后开始增加。麦莎两次东折受环境风场的变化影响都比较大。麦莎移动路径与24 h负变高中心的位置变化比较一致,两次东折时更是如此。麦莎第一次东折时,与高空辐散场也有很大的关系。

The reasons why do the two turnings eastward of typhoon Matsa’s track happen are analyzed from the relations between the western Pacific subtropical high area index,the moving speed of Matsa and the moving direction of Matsa respectively,the wind field,the upper air divergence field,and the high altitude divergence field,by using 1°×1°NCEP reanalysis data.The results show that when the two turnings eastward occur,the subtropical high area index is increasing;before the two turnings eastward,the moving speed of Matsa is increasing,but after the two turnings eastward,the moving speed of Matsa is decreasing.Then,the effects of the wind field’s changes on the two turnings eastward of Matsa are both greater.Futher more,the moving direction of Matsa is more in accordance with the negative height change center position within 24 hours,especially when the two turnings eastward happen.It is also found that Matsa’s first turning eastward is related to the upper air divergence field.