利用云南地区32个站日降水量资料、NCEP/NCAR月平均大气环流资料和ERSST V3b的海表温度资料, 利用合成分析、相关分析等方法, 研究了影响云南雨季降水的太平洋-印度洋海温分布模态, 并讨论了ENSO和热带印度洋偶极子(IOD)对云南雨季降水多寡影响的相对重要性, 最后讨论了太平洋-印度洋海温分布型对云南雨季降水影响的物理机制。结果表明, 热带太平洋ENSO和 热带印度洋IOD对云南雨季降水多寡均有影响, 但是热带印度洋IOD的影响更为重要。当热带西印度洋海温偏高明显(IOD正位相)时, 在热带印度洋上有一偏东风, 热带西印度洋上为一气旋性距平环流, 其上的印度洋的暖湿气流向北进入大陆, 然后经由高原南侧并由北向南进入孟加拉湾, 从而抑制了孟加拉湾南支槽的发展和孟加拉湾暖湿空气向我国云南地区的输送, 使得云南上空为水汽通量辐散区, 降水偏少; 当热带印度洋海温偏低且热带印度洋东西海温梯度表现为IOD负位相时, 热带印度洋上没有偏东风, 孟加拉湾槽偏强, 向我国云南地区的水汽输送也偏强, 云南上空为水汽通量辐合区, 降水偏多。

Based on seven stations’ monthly precipitation data in Yunnan and the NCEP/NCAR monthly atmospheric circulation data, as well as ERSST V3b monthly sea surface temperature (SST) data, the Indian-Pacific SST mode that impacts Yunnan precipitation during rainy season was investigated using composite and correlation analysis. Of El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) mode, which plays a more important role on Yunnan precipitation in rainy season? Finally, the physical mechanism through which Indian-Pacific SST mode impacts Yunnan precipitation in rainy season was discussed. The results are as follows. Both ENSO and IOD have influences on Yunnan precipitation in rainy season, but the IOD plays a more important role. When the western India Ocean’s SST is warmer (positive IOD), the easterly wind appears in the tropical Indian Ocean and a cyclonic anomalous circulation is in the western Indian Ocean. The warm and moist airflow in the western Indian Ocean enters the Mainland China along the west side of the Tibet Plateau, then goes around the Tibet Plateau and from the north to the south, and finally enters the Bay of Bengal, which limits the development of the trough over the Bay of Bengal. So, the water vapor transportation to Yunnan is less. Yunnan is in the water vapor flux divergence area and has less precipitation. When the tropical Indian Ocean has lower SST (negative IOD), no easterly wind is in the tropical Indian Ocean, the trough over the Bay of Bengal is strong, and the water vapor transportation to Yunnan is more; Yunnan is in the water vapor flux convergence area and has more precipitation.