1971-2012年珠穆朗玛峰地区极端降水事件变化研究

Variation characteristics of extreme precipitation events over Mt.Qomolangma region in China from 1971 to 2012

利用西藏珠穆朗玛峰地区5个气象站点1971-2012年逐日降水量资料,采用滑动平均、线性回归、Mann-Kendall非参数检验和Morlet小波分析等方法,分析了珠穆朗玛峰地区极端降水事件的时空变化特征.结果表明：1971-2012年42 a来,珠穆朗玛峰地区大部分极端降水指数呈现出自东向西逐渐增大的空间分布格局,连续干旱日数、连续湿日和降水强度表现为增加趋势,其他极端降水指数趋于减少.其中,强降水量、极强降水量和年降水总量减幅较大,分别为-5.74 mm·（10a）-1、-1.20 mm·（10a）-1和-5.32 mm·（10a）-1,在喜马拉雅山南坡的聂拉木站表现的最为明显.大部分极端降水指数在21世纪最初的10 a减幅最大,在30 a际尺度上也表现为减少趋势.除连续干旱日数外,极端降水与年降水总量关系密切.各项极端降水指数都存在3~4 a显著周期,也存在10 a、12 a和15 a的周期.在时间转折上,各项极端降水指数均未发生气候突变.

Variations in extreme climate events are more sensitive to climate change than the mean values, and so have received much attention. In this study, the features of ten indices of precipitation extremes over Mt. Qomolangma region in China were examined broadly based on daily precipitation data during the period of 1971 -2012 from 5 meteorological stations. The methods of inverse distance weighted （IDW）, 10-year smoothing average, linear regression, Mann-Kendall test and continuous wavelet transform were employed to delineate the rate of change, abrupt change points, statistical significance of the trends, and periodicity of extreme precipitation indi- ces. It is found that spatially, the most extreme precipitation indices increase from west to east. In recent 42 years, the consecutive dry days （CDD）, consecutive wet days and simple daily intensity index have increased, but the other extreme precipitation indices have decreased. Among them, the very wet day precipitation, ex- tremely wet day precipitation and the annual total precipitation have presented a larger decreasing trend, with the rates of -5.74 mm · （10a） -1, - 1.20 mm· （10a） -1and - 5. 32 mm· （10a） -1, respectively, especially in the Nyalam station on the southern slopes. On the decadal scale, the maximum decreasing extreme precipitation indices were in the 2000s; on the 30 years scale, there was also a decreasing trend on. Except for CDD, the ex- treme precipitation indices were closely associated with annual precipitation in Mt. Qomolangma region. There were obvious periods of 3 to 4 years for all extreme precipitation indices, together with periods of 10 a, 12 a and 15 a. Additionally, it was found with abrupt change test that all extreme precipitation indices have not abrupt change.