1979～2016年西南地区夏季持续性降水的变化特征

本文基于1979～2016年西南地区25个站点的逐日降水资料分析了西南地区夏季降水和持续性降水的变化特征，得到的结论如下:(1)西南地区夏季降水总天数总体呈减少趋势，无雨时段平均持续天数总体呈增加趋势，有雨时段平均持续天数仅川内呈增加趋势。(2)长、短持续性降水平均持续天数均呈减少趋势，其中长持续性降水平均持续天数减少趋势显著。各站长、短持续降水事件的总降水天数占持续性降水总天数的比例呈南北反向的变化趋势，长(短)持续降水事件的总天数占持续性降水总天数的比例呈北增(减)南减(增)。(3)长、短持续性降水异常年差值合成环流的相似之处:在对流层低层，我国东南部存在气旋性环流异常，与我国北方反气旋性环流在西南地区产生辐合。垂直速度场均为负异常(< -0.015Pa/s)-上升运动。上述结论可为气象灾害预测、预警提供线索。 

The Variation Characteristics of Summer Sustained Precipitation in Southwest China from 1979 to 2016

Based on the daily precipitation data of 25 stations in the Southwest China from 1979 to 2016, this paper analyzes the characteristics of summer precipitation and continuous precipitation in the Southwest China. The conclusions are as follows: (1) The total number of summer precipitation days in the Southwest China is generally decreasing. The average number of days during the period with no rain showed an increasing trend, while the average number of days during the rainy period showed an increasing trend only in Sichuan. (2) The average duration of long and short continuous precipitation is decreasing, the average duration of long and continuous precipitation is decreasing significantly. The proportion of the total precipitation days of long continuous precipitation events and short continuous precipitation events to the total days of continuous precipitation shows a trend of north-south reverse. What’s more, the proportion of total days of long (short) continuous precipitation events to the total days of continuous precipitation events is increasing in the north (decreasing) and decreasing in the south (increase). (3) The similarities of the combined circulations in the anomalous years between long continuous precipitation and short continuous precipitation: In the lower troposphere, there is a cyclonic circulation anomaly in southeastern China, which converges with the anticyclonic circulation in northern China in the southwest.The vertical velocity fields are all negative anomalies (< -0.015 Pa/s)-ascending motion.The above conclusions can provide clues for meteorological disaster prediction and early warning.