摘要
利用西南地区四川、重庆、云南和贵州秋季降水量和日照时数资料,对西南地区秋雨极端天气气候事件的监测指标进行了探讨,最终定义连续5天以上日降水量大于等于0.1mm,且日照时数小于等于0.1h的天气过程为1次秋雨事件。以此指标得出西南秋雨事件主要发生在四川盆地中南部、重庆西部、云南东北部和贵州北部等地区,秋雨最强中心平均每年发生华西秋雨事件可达1.6次以上,年平均秋雨日数大于11天。近50年西南秋雨强度呈波动下降趋势。结合NCEP/NCAR同期的位势高度场、水汽场以及风场资料对西南秋雨的成因分析表明:在秋雨强年,500hPa高度场上极区气压偏高,中纬地区气压偏低,西风环流较弱,副高脊线易偏北,印缅槽较深。850hPa高度场上在西南秋雨较强的区域有一个明显的水汽汇,在风场上也有较强的来自孟加拉湾和印度洋水汽输送。垂直经圈环流和纬圈环流有明显的上升运动与之配置。
By using the data of precipitation and sunshine duration in Sichuan, Chongqing, Yunnan and Guizhou over Southwest China, the monitoring indexes of autumn rainfall over Southwest China for extreme weather and climate events are discussed. An autumn rain event is defined as： with the number of successive rainy days greater than 5; the amounts of precipitation more than 0.1 mm; and the sunshine duration less than 0.1 hour. This index can describe the disaster characteristics of continuity and less sunshine of autumn rain events over Southwest China. The results indicate that autumn rain events in Southwest China happen mainly in the middle and south of the Sichuan basin, western Chongqing, northeastern Yunnan and northern Guizhou, with the occurrence frequency being more than 1.6 times per year in the central area of the region and the average number of rainy days being over 11. The intensity of autumn rainfall over Southwest China exhibits a downtrend with fluctuation. Combining with the simultaneous NCEP/NCAR data of the geopotential height fields, water vapor field and wind data, the causes of autumn rainfall over Southwest China are systematically analyzed. The results indicate that in severe autumn-rain years, the pressure at 500 hPa in the polar zone is quite high, and the subtropical ridge line is northward and the Indian and Burma trough is deeper. In the area where the autumn rain is severe, there is an obvious water vapor convergence at 850 hPa over Southwest China. There is an upward motion working along with the vertical latitudinal and longitudinal circulation.
出处
《气象科技》
2013年第5期883-888,共6页
Meteorological Science and Technology
基金
国家自然科学基金面上项目"华西秋雨年际变化规律及其形成机理研究"(41275097)资助
关键词
西南秋雨
监测指标
大气环流
水汽输送
autumn rain over Southwest China, monitoring index, atmospheric circulation, watervapor transfer
