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以同年是否发生印度洋偶极子(IOD)正位相事件为标准,本文将El Nio Modoki事件分为纯El Nio Modoki事件(p-ENM)、El Nio Modoki与IOD同时发生的事件(ENM-IOD)两类。选取了1979~2012年间较为显著的两次p-ENM事件(2004;2009)和两次ENM-IOD事件(1991;1994),对比发现:同类事件西北太平洋秋季热带气旋生成地的分布类似,但相比p-ENM事件,ENM-IOD事件的热带气旋生成地明显偏东。p-ENM秋季,西北太平洋西风异常较弱且局限在165°E以西,范围较窄;而ENM-IOD秋季,西风异常强劲,并向东越过日界线。这使得ENM-IOD秋季季风槽东侧与p-ENM相比东伸20°。同时,p-ENM秋季垂直风切变相对ENM-IOD秋季而言强度小,大值区窄,前者条件下热带气旋在西侧生成的可能性相对要大。季风槽位置和垂直风切变分布的差异,使得ENM-IOD秋季热带气旋生成地较p-ENM秋季明显偏东。
Based on the occurrence of the positive phase of the Indian Ocean dipole (IOD) in the same year, El Nio Modoki events were divided into pure El Nio Modoki events (p-ENM) and El Nio Modoki Events (ENM-IOD) two categories. A comparison was made between the two p-ENM events (2004; 2009) and the two ENM-IOD events (1991; 1994), which were notable between 1979 and 2012. The comparison shows that the distribution of tropical cyclone in the autumn of the Northwest Pacific is similar Compared with the p-ENM event, the tropical cyclone of the ENM-IOD event was obviously eastward. In the autumn of p-ENM, the westerly wind anomalies in the western North Pacific were weaker and limited to the west of 165 ° E with a narrower range. In the autumn of ENM-IOD, the westerlies were extremely strong and crossed the daily limit eastward. This caused the eastern side of the ENM-IOD autumn monsoon trough to extend 20 ° eastward from the p-ENM. Meanwhile, the p-ENM fall vertical wind shear is less intense and larger in the fall of ENM-IOD, and the former is more likely to be generated on the west side of the tropical cyclone. Differences in the locations of monsoon troughs and vertical wind shear distribution made the ENM-IOD fall tropical cyclone more obvious than the autumn of p-ENM in autumn.