青藏高原近40年来的降水变化特征

Precipitation changes in the Tibetan Plateau during the last four decades

利用我国青藏高原地区的1961-2000年56个气象站的逐月降水资料,通过计算降水量的距平百分率,分析了青藏高原自1961至2000年以来降水量变化的趋势和1961-2000年以来各季降水量变化趋势,发现:青藏高原近40年来降水量呈增加趋势,降水量的线性增长率约为1.12mm/a。再将高原划分为四个季节,分析了各季40年来的降水量的变化情况得出:春季降水量年际变化较大,秋季降水量变化不明显。夏季降水量值较大而降水变化幅度较小,冬季降水量变化则与夏季相反。通过将青藏高原分为南北两个地区,分析了两个区的年降水量和四个季节的降水量的变化得出:高原南区1961-2000年降水量呈增加的趋势,降水量的线增长率为1.97 mm/a,春季和冬季降水量年际变化较大,夏季降水量变化不明显,秋季降水量略有增加;北区年降水量和夏季的降水量变化较小,秋季降水量的年际变化较大,冬季降水量变化最大。对青藏高原的南北两区用Mann-Kendall方法进行突变分析,显示高原南区分别在1978年和1994年发生突变,北区没有发现突变。

By computing percentage anomalies of monthly rainfall data from fifty-six stations located in the Tibetan Plateau, precipitation change tendency from 1961 to 2000 is analyzed. The result shows that the annual precipitation increases during the forty years and the linear growth rate is 1.12 mm per year. Furthermore, the seasonal precipitation change tendency is analyzed and the conclusion indicates that the interannual variation of the precipitation in spring is great and the precipitation change in autumn is unobvious. The precipitation variation in summer is great and the precipitation change in winter is opposite to that in summer. Dividing Tibetan Plateau into southern and northern regions, the paper analyzed precipitation changes in the two regions from 1961 to 2000. The result shows that the annual precipitation in southern region increases during the forty years and the linear growth rate is 1.97 mm per year. The precipitation change tendency in southern region is analyzed further and the result shows that the interannual variation of the precipitation in spring and winter is great, the precipitation change tendency in summer is not obvious and the precipitation in autumn rises slightly. In northern region, the annual precipitation variation and the precipitation change of the summer are small. The interannual variation of the precipitation in autumn is great and the change of the precipitation in winter is the biggest in four seasons of the northern area. The abrupt change is analyzed with Mann-Kendall method in the whole, the southern and the northern region. The abrupt change is detected in 1978 at the Tibetan Plateau and there is an abrupt change of precipitation at the southern region in 1994 and the abrupt change is not detected in northern region.