【摘要】 随着全球气候的改变,由极端降水事件所引发的干旱、洪涝、泥石流等自然灾害,引起了社会各界的广泛关注。本文基于雅鲁藏布江流域19个气象站点1973—2016年的逐日降水数据,使用线性倾向估计法、MannKendall非参数统计检验法和皮尔森相关系数法,分析了雅鲁藏布江流域极端降水事件的时空变化特征及其与印度洋偶极子指数(DMI)的相关性。结果表明:(1) 1973—2016年间,雅鲁藏布江流域极端降水指标整体上呈现出上升趋势,与流域内年平均降水量变化趋势相一致,其中降水日数(RD)、降水总量(PRCPTOT)、极端降水量(R95p)、连续湿润日数(CWD)指标均在95%信度水平上显著上升。RD、CWD极端降水指标分别在1995年左右、2001年左右发生了突变;(2)雅鲁藏布江流域的极端降水指标在空间上存在明显的差异性,表现出从东部到西部逐渐递减的分布特征。极端降水指标在雅鲁藏布江流域的空间分布特征表明,近年来,东部湿润地区暴雨事件可能更加频繁,洪涝灾害更加严重,西部地区则从相对干旱逐渐变得相对湿润;(3)对极端降水指标进行主成分分析,PRCPTOT和CWD指标的载荷在主成分1和主成分2中分别占0.94、0.71,表明可以用它们分别代表极端降水事件的降水量级和降水持续性;(4) 1—3月份的极端降水事件更容易受到印度洋偶极子(IOD)的影响,在雅鲁藏布江流域中部地区,2月份的DMI与PRCPTOT、CWD呈现出正相关关系,相关系数分别达到0.412和0.356,是易受DMI影响的主要地区。雅鲁藏布江流域在250 h Pa和500 h Pa的位势高度差值均存在负值中心,有利于极端降水事件的发生。研究结果为雅鲁藏布江流域水资源管理和灾害防治提供科学基础。更多还原

【Abstract】 Precipitation plays an important role in hydrological and energy cycle.With the global climate changes,extreme precipitation events in the worldwide are increasing frequently.Therefore,it is essential to estimate extreme precipitation events,especially in the Qinghai-Tibet Plateau.The correlation between the spatiotemporal variations of the extreme precipitation and the DMI(Dipole Mode Index) of NOAA(National Oceanic and Atmospheric Administration) were analyzed by using the linear regression,Mann-Kendall,and correlation analysis methods,based on the daily precipitation data from 1973 to 2016 at 19 meteorological stations in the Yarlung Zangbo River basin.The results showed that the values of the extreme precipitation indices presented an increasing trend from 1973 to 2016,which was consistent with the trend of the average annual precipitation variation.Specifically,all of the indices including the RD(days of precipitation),PRCPTOT(annual total wet-day precipitation),R95p(very wet days),CWD(consecutive wet days) showed the significant increasing in a confidence level of 95%,while the RD and the CWD extreme precipitation indices experienced abrupt changes around 1995,and 2001;(2) The spatial differences of the extreme precipitation indices were obvious,which showed a decreasing tendency from the west to the east in the Yarlung Zangbo River basin.In recent years,the heavy precipitation events may be more frequent in the eastern humid areas,which may cause more flood disasters,and the western relative arid areas became relatively humid;(3) The results of the principal component analysis showed that PRCPTOT and CWD explained variances of 94% and 71%,which revealed they can be used to characterize the extreme events;(4) DMI was significantly and positive correlated to the precipitation in the most parts of the Yarlung Zangbo River basin.The correlation coefficients between DMI and PRCPTOT were greater than 0.4,and the correlation coefficients between DMI and CWD were greater than 0.3 in parts of the central areas.There was a negative low value center in the geopotential height difference of 250 h Pa and 500 h Pa over Yarlung Zangbo River basin,which promoted the occurrence of extreme precipitation events.Studying extreme precipitation events and its influencing factors can provide useful information for flood control and water resources management.更多还原