海温异常对云南5月降水主要模态的影响

利用1961~2016年云南125个气象观测站逐月降水数据，结合同期NCEP/NCAR再分析资料和英国Hadley中心海表温度资料，在揭示云南5月降水主要模态特征的基础上，分析发现北太平洋、赤道中东太平洋和赤道印度洋是影响云南5月降水的三个主要关键海区，由此定义了对应不同关键区的类PDO指数、类ENSO指数、Dsst指数和Esst指数，进一步探究云南5月降水主要模态与海温异常的关系。结果表明:（1）云南5月降水的主要模态为全区一致型和东西差异型，其中东西差异型模态表现出明显不对称特征，东多西少时的东西差异特征比较明显，而东少西多时西部地区降水偏多的范围很小，主要以中东部地区降水偏少为主。（2）北太平洋地区的类PDO和类ENSO海温异常模态是影响云南降水全区一致型变化的主要因子，类PDO主要影响水汽输送变化，而类ENSO主要影响冷空气活动，即当北美沿岸海温偏低、北太平洋中部海温偏高和赤道中东太平洋海温偏低时，有利于云南全区一致型降水偏多，反之则有利于降水偏少。（3）Dsst指数表征的赤道印度洋海温变化是影响云南降水出现东西差异的主要因子，当印度洋海温偏高时，有利于云南降水西多东少，反之则有利于云南降水西少东多，而Esst指数表征的赤道中东太平洋海温变化却会减弱Dsst指数对降水东西差异型的影响，使云南降水更趋向于全区一致型的变化。 

Influence of SSTA on Main Precipitation Patterns in Yunnan in May

Based on the precipitation data of 125 meteorological observation stations in Yunnan, NCEP / NCAR reanalysis atmospheric circulation and sea surface temperature (SST) of Hadley Center in England, the main precipitation patterns in Yunnan in May are analyzed. It is found that the North Pacific, the equatorial Middle East Pacific and the equatorial Indian Ocean are the three main key regions affecting precipitation in May in Yunnan. The PDO-like index, ENSO-like index, Dsst index and Esst index are defined, and the relationship between the main precipitation modes in May and SST anomaly (SSTA) in Yunnan is further analyzed. The results show that: (1) The main precipitation patterns include regional consistency and East-West difference, the East-West difference pattern displays obvious asymmetry when the precipitation in the East is more than that in the West, while the range of precipitation in the western region is small when the precipitation in the East is less than that in the West, mainly characterized by less precipitation in the middle and eastern region. (2) The PDO-like and ENSO-like SSTA modes in the North Pacific are the main factors affecting the consistent precipitation change in Yunnan. PDO-like mainly affects the change of water vapor transport, while ENSO-like mainly affects the cold air activity. That is, the SSTA is conducive to more consistent precipitation in Yunnan, and vice versa. (3) The equatorial Indian Ocean SSTA represented by the Dsst index is the main factor affecting the East-West difference in precipitation in Yunnan. When the Indian Ocean SSTA is positive, it is conducive to more precipitation in the West and less in the East. On the contrary, it is conducive to less precipitation in the West and more in the East in Yunnan. However, the equatorial Middle East Pacific SSTA represented by the Esst index will weaken the impact of the Dsst index on the East-West difference in precipitation, so that the precipitation in Yunnan tends to be consistent in the whole region.