西藏近50年极值降水变化趋势

Variation Trend of Extreme Precipitation in Tibet During Recent 50 Years

为进一步揭示西藏极端降水变化趋势及特征,为防灾减灾提供参考依据。利用西藏1961—2010年18个有连续气象观测记录站点的逐日降水资料,分析了7个序列降水统计量的变化趋势。发现近50年,西藏平均年降水日数为弱的增多趋势,最长连续降水日数为弱的减少趋势,最长连续降水总量变化趋势不明显,1日和3日最大降水量为弱的增大趋势,年降水量、平均降水强度、强降水日数均为显著增加趋势;平均降水强度显著增大和强降水日数显著增多,是西藏平均年降水量显著增大的最主要原因;西藏的西部和沿江上游地区年降水量减少且趋于集中,干日增多,干期增长,干旱化趋势更加严重。其他大部分地区年降水量增多,平均降水强度增大,强降水日数增多,短时强降水引发的洪涝等灾害可能趋于增多。

The paper aims to reveal the variation trend and characteristics of extreme precipitation in Tibetand provide references for disaster prevention and mitigation. With daily precipitation observation data of 18 meteorological stations in Tibet during 1961-2010, the variation trends of 7 variables in Tibet AutonomousRegion were investigated. The results showed that： The results showed that： the mean annual precipitation dayindicated slightly increasing variation and the longest continuous precipitation day presented weak decreasingvariation trend in recent 50 years while the total precipitation amount had no obvious variation. The maximumprecipitation in one day and three days exhibited a slightly increasing trend. The annual precipitation, meanprecipitation intensity and strong precipitation days presented a significantly increasing trend. The increase ofthe mean precipitation intensity and the strong precipitation days were the major reason for a remarkablyincreasing trend of the precipitation in Tibet. The precipitation showed a decreasing trend in western Tibet andthe upper reaches of Yarlungzangbu River, where the days without rainfall increased and the dry season wasmuch longer than before, and the desertification became more serious. The annual precipitation, the meanprecipitation intensity and the strong precipitation days increased in most parts of Tibet, and the flood andwaterlogging caused by the strong precipitation in short time might increase.