1981~2019年西藏极强降水的时空变化特征

Spatio-Temporal Variations of Extremely Heavy Precipitation in Tibet during 1981~2019

极强降水量是造成气象灾害的重要原因之一,利用1981~2019年西藏自治区(简称西藏) 38个气象台站逐日降水量资料,分析了西藏近39年来极强降水频数及强度的时空变化特征,结合Mann-Kendall检验对极强降水频数和强度突变特征进行检验。结果表明:西藏极强降水存在显著空间分布特征,极强降水事件阈值主要呈现东南部及南部边缘聂拉木地区较大,西北部及南部错那地区较小的趋势;由于地势和气候背景等影响,西藏南部和东南部地区极强降水偏多,西部地区极强降水偏少。同时西藏极强降水存在明显的季节与年代际变化特征,极强降水四季的频数及强度差异较大,研究时间段内极强降水频数和强度整体呈现出缓慢增长的趋势,Mann-Kendall检验表明极强降水频数及强度出现交点较多,整体呈现缓慢上升的变化趋势;主要从 1984年出现突变。

Extreme heavy rainfall is one of the main meteorological disasters. Using 38 weather stations’ daily rainfall data from 1981 to 2019 in Tibet, analyzing the extremely heavy rainfall frequency and intensity in recent 39 years, and the Mann-Kendall test was also used to test the extremely heavy rainfall frequency and intensity jump characteristics. The results indicated that extremely heavy rainfall has obvious spatial distribution in Tibet, the threshold values of extremely heavy precipitation events mainly show a larger trend in the southeastern and southern border areas of Nyalam County, and a smaller trend in the northwestern and southern Cuona areas. Because of the geomorphology and climate, the south and southeast of Tibet have more extremely heavy rainfall than the west. Meanwhile, extremely heavy rainfalls also have an obvious seasonal and annual change, and the frequency is different obviously in the four seasons. The Mann-Kendall test showed that the frequency and intensity of extremely heavy precipitation had many intersections, and the overall trend was slowly rising. The mutation occurred in 1984.