The interannual variability of precipitation during the summer monsoon transition over the Indochina Peninsula (ICP) is substantially influenced by the sea surface temperature anomalies (SSTAs) of the tropical ocean, showing a robust relationship between April and May (AM) precipitation and the El Niño/Southern Oscillation (ENSO) phenomenon. Dynamic composites and statistical analyses supported by model experiments indicate that the observed anomalous AM precipitation is associated with circulation anomalies over the Pacific and, in addition, affected by the response to the tropical SSTAs forcing from the Indian Ocean (IO): (i) Less (greater) than normal AM precipitation over the ICP occurs during the El Niño (La Niña) years, which is consistent with late (early) Bay of Bengal (BoB) summer monsoon onset. (ii) The dry (wet) AM precipitation years are associated with the anomalous western North Pacific (WNP) anti-cyclone (cyclone) induced by El Niño (La Niña) concurrent with the anti-cyclone (cyclone) over the BoB, suppressing (favoring) the meridional flow of warm and moist air from the Pacific and Indian ocean and thus cutting (providing) moisture supply for the ICP. (iii) The reduced tropical convective activity over Maritime Continent (MC) is related to the weakened local Hadley circulation concurrent with the weakened overturning Walker circulation, and favors a drier than normal AM precipitation over the ICP, to which the wetter years are opposite. These symmetric atmospheric circulation patterns characterizing dry and wet AM precipitation over the ICP are also reproduced by numerical experiments with an atmospheric general circulation model.

中南半岛夏季风过渡期间降水的年际变化受到热带海洋海面温度异常（SSTAs）的显着影响，显示出 4 月和 5 月（AM）降水与厄尔尼诺现象之间的密切关系/南方涛动（ENSO）现象。模型实验支持的动态复合和统计分析表明，观测到的异常 AM 降水与太平洋上的环流异常有关，此外，还受到来自印度洋 (IO) 的热带 SSTA 强迫响应的影响：(i) 较少在厄尔尼诺 (La Niña) 年期间，ICP 上出现（大于）正常的 AM 降水，这与晚（早）孟加拉湾 (BoB) 夏季风爆发一致。(ii) 干（湿）AM 降水年与由厄尔尼诺（La Niña）引起的异常西北太平洋（WNP）反气旋（气旋）与 BoB 上的反气旋（气旋）同时发生，抑制（有利于）来自太平洋和印度洋的暖湿空气的经向流动，从而减少（提供）ICP的水分供应。(iii) 海洋大陆（MC）热带对流活动减少与局部哈德利环流减弱以及翻转沃克环流减弱有关，并且有利于ICP上空比正常AM降水更干燥，而湿润年份则相反。这些表征 ICP 上干湿 AM 降水的对称大气环流模式也通过大气一般环流模型的数值实验再现。