Interannual Variation in Indochina Summer Monsoon Rainfall: Possible Mechanism

Indochina is located between two extensively researched components of the Asian monsoon system: the Indian subcontinent and southeast–east Asia. Highly correlated with the National Oceanic and Atmospheric Administration Niño-3 sea surface temperatures, the interannual variation of Indochina monsoon rainfall is caused by a mechanism different from the two aforementioned regions. This mechanism consists of two elements: 1) the interannual modulation of the occurrence frequency of westward-propagating weather disturbances in the South China Sea–western tropical Pacific by an anomalous short-wave train emanating from the western tropical Pacific, and 2) an east–west interannual seesaw of the global divergent water vapor flux induced by the interannual variation in the global divergent circulation. An effort is made in this study to illustrate this mechanism.