近53 a云南东部春季旱涝及其环流距平波列影响

基于年度春季降水，用旋转经验正交函数（REOF）方法,将云南省划分为3个降水气候区，分析了近53 a云南东部春季旱涝基本特征，选取帕默尔干旱指数（PDSI）对春季旱涝进行评估。小波分析发现，云南东部春季旱涝存在准14 a周期，并可分为3个时期：1958-1980年干旱期，1981-2000年偏涝期，2000年以后干旱期。对云南东部涝(旱)年合成分析显示，大尺度背景高度场、风场和温度场的距平场都存在2列并行的纬向波列。在涝年,500 hPa位势高度距平纬向波动为高纬度正距平,中纬度负距平，显示云南上空的低值系统活跃。风场距平波列性质为中高纬度负距平，中低纬正距平，显示南支槽水汽输送的速度与量值的强盛。700 hPa温度场距平波列为高纬正距平，中纬负距平，显示云南温度偏冷，与低纬度副高控制的海洋暖湿气团形成系统性锋区,有利于云南东部降水。在旱年，则2列并行纬向距平波列各要素性质正好相反。此外,青藏高原上游风速受山脉西南侧地形阻挡发生向南折射，涝年风速强,旱年风速弱，直接促发和影响南支槽的强弱。上游风速与南支槽强度具有正比关系。降水关键系统昆明准静止锋在背景纬向波列环境中，涝年比旱年出现频次高，维持时间长。

Influences of Drought,Flood and Zonal Circulation Anomaly over East Yunnan Province in Spring in Recent 53 Years

The characteristics of drought and flood over east Yunnan Province, China in spring in recent 53 years were analyzed. Yunnan was divided into three rainfall climate regions by REOF method based on the data of rainfall in spring, and the location and area range of the eastern region was determined. The index of PDSI was chosen to describe drought and flood in east Yunnan after compared with other two kinds of drought index only based on rainfall. By applying Morlet Wavelet Method, it was found that there was an obvious 14 years fluctuation period of drought and flood in east Yunnan in recent 53 years, and the time series could be divided into three periods: drought period from 1958 to 1980, flood period from 1981 to 2000, and another drought period after 2000. The synthetic analysis on drought and flood over east Yunnan showed that there were two parallel zonal waves in the circulation background anomaly fields of geo height, zonal wind and air temperature. In flood years, the high latitude wave was positive but the mid latitude one was negative for geo height anomaly field at 500 hPa, which revealed that the low systems over Yunnan were active. For zonal wind anomaly field at 500 hPa, the high mid latitude wave was minus and the mid low latitude one was plus, which revealed that the south branch trough over the south of the Qinghai-Tibetan was strong at both velocity and transferred moisture amount. For the temperature anomaly field at 700 hPa, the high latitude wave was positive and the mid latitude one was negative, which showed that the temperature over Yunnan was lower than normal and formed a temperature front with warm humid air mass of sub tropic high over low latitude ocean. It was benefit to the generation of front precipitation in east Yunnan. In drought years, properties of all the factors were opposite to those in flood years for the two parallel zonal waves at anomaly fields. It needs to be emphasized that a southward refraction occurred when the upstream zonal wind was blocked by the southwest boundary of the Qinghai-Tibetan Plateau. Strong wind in flood years and weak wind in drought years affected directly by the intensity of the south branch trough, and the upstream wind intensity and the south branch trough intensity were proportional. The key precipitation system over east Yunnan in spring was the Kunming quasi stationary front. Within the background anomaly waves, the front showed that its occurring frequency and duration were higher and longer in flood years than those in drought years.