利用NCEP/NCAR再分析资料及NOAA OLR、 海温距平等资料, 分析华西秋雨极端偏强年2017年季风环流的异常特征及其影响, 并探讨季风环流异常机制。结果表明: （1）2017年, 南亚高压偏强偏北偏东, 西北太平洋副热带高压偏强偏北偏西, 东南亚西南季风和南海东南季风均偏强, 与干空气共同作用形成极端偏强秋雨。（2）赤道西太平洋和中东太平洋海温正负距平对比鲜明, 从而形成偏强Walker环流, 使得赤道西太平洋和南海台风活跃, 并形成强热源; 热源中心上升气流与10°S以南热带下沉气流形成强大次级环流圈; 多种因素共同加强西北太平洋副热带高压及东南季风, 并引导赤道西太平洋和南海水汽进入华西地区。（3）青藏高原冷空气势力弱, 感热强, 其东部到华西地区对流凝结潜热强, 因而热源明显偏强, 大气中高层温度显著偏高, 有利于南亚高压、 西北太平洋副热带高压和西南季风偏强, 是该年华西极端秋雨的另一重要因素。（4）本个例赤道太平洋海温异常变化发生在盛夏后期, 超前于西北太平洋副热带高压由弱变强一个月左右, 海温过程性变化对于短期气候预测和延伸期预报具有特别重要的指示意义。
NCEP/NCAR reanalysis data and NOAA OLR, Sea Surfact Temperature Anomalies (SSTA) data were used here to analyze the anomalous features of summer monsoon circulations in 2017 with extremely strong autumn precipitation Huaxi over western China, and to explore the mechanisms.The results show that WPSH is stronger and more northwestward, SAH (South Asia High) is stronger and more northeastward, Southwest Monsoon and Southeast Monsoon are both stronger, converge to Huaxi and meet with dry air, and work together to form an extreme strong autumn rain.The SST in the western equatorial Pacific and the Middle East have the positive and negative anomalies contrasted sharply, resulting in a strong Walker circulation, which made the typhoon in the western equatorial Pacific and the South China Sea active and formed a strong heat source.The central ascending airflow forms a strong secondary circulation with the tropical subsidence airflow south of 10°S; Various factors jointly strengthen WPSH and the southeast monsoon and guide the western Pacific and South China Sea water vapor into Huaxi.The cold air of Qinghai-Tibetan Plateau was weak with strong sensible heat.The convective and condensation latent heat was strong over northeastern Qinghai-Tibetan Plateau and Huaxi.So that the heat source was obviously stronger with significantly higher upper middle level temperature.It is beneficial to SAH, WPSH.It is another important reason for extreme heavy rain over Huaxi.In this case, the anomalous variation of the equatorial Pacific SST occurred in the late summer, one month before WPSH’s changing from weaker to stronger and is particularly important for short-term climate prediction and extended forecast.
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