云南雨季的时空特征及与大气环流变化的关系

为了系统了解和认识云南雨季变化的气候特征、年际特征及其影响因子，利用云南116个气象观测站1961—2015年20时—20时的逐日降水资料，根据新定义的西南雨季单站标准，系统分析云南雨季变化的时空特征以及相应的大气环流特征。结果表明:（1）对于1981—2010年的气候平均，云南全省平均雨季的开始和结束日期分别为5月22日和10月15日，雨季变化的空间差异较大，雨季开始大致表现为从东南向西北推进，结束则从西北和东南逐渐向西南推进，由此导致云南雨季长度和雨季总降水量变化由南至北逐渐减小；（2）云南雨季变化的年际差异显著，全省平均雨季开始日期最早在5月8日，最晚在6月8日，结束日期最早在9月30日，最晚在11月2日，早晚相差近1个月；（3）云南雨季开始日期主要受西南季风和中纬度冷空气活动的共同影响，季风建立偏早和中纬度冷空气活动频繁有利于雨季开始早，反之有利于雨季开始晚；而雨季结束日期主要受热带季风环流变化的影响，夏季风向冬季风季节转换早则云南雨季结束早，反之雨季结束晚。 

STUDIES ON SPATIAL-TEMPORAL CHARACTERISTICS OF YUNNAN RAINY SEASON AND ITS RELATIONSHIP WITH ATMOSPHERIC CIRCULATION

Based on the station standard of southwest rainfall season, the temporal and spatial features of Yunnan rainy seasons were investigated using 116 meteorological observation stations data from 1951-2015. At the same time, the influence of atmospheric circulation on Yunnan rainy seasons were further studied. The results are shown as follows: (1) For the 30-year (1981—2010) climatic mean, the beginning and ending date of Yunnan averaged rainy seasons are respectively on May 22 and October 15. The spatial differences of Yunnan rainy season variation are obvious in different region. The rainy season begins gradually from the southeast to the northwest and ends gradually from the northwest and southeast to the southwest, causing the length and total precipitation of the rainy season to decrease gradually from the south to the north; (2) For the beginning and ending date of annual rainy seasonsin Yunnan for 1961—2015, the earliest beginning date is May 8th and the latest date is June 8th. The endingdate is as early as September 30th and the latest November 2nd; (3) The changes of Yunnan rainy seasons are influenced jointly by the southwest monsoon and mid-latitude cold air. The early (late) establishment of southwest monsoon and frequent influence of cold air coming from the mid-latitude region may result in an early (late) rainy season. Different from the start of the rainy season, the end of a Yunnan rainy season is mainly affected by the tropical monsoon circulation. With early (late) shift of seasonal circulation from summer monsoon to winter monsoon, the Yunnan rainy season ends early (late).