中国西部年降水量的气候变化

中国西部大部分处于干旱、半干旱地区,而且降水量长期变化剧烈。论文综合整理了17个年降水量代用资料序列,其中11个为树木年轮,4个为史料,2个为冰芯积累量。所有序列均采用10年平均值,对1880～1979年的100年平均求每10年平均百分率距平。EOF1表明河套以西到祁连山北部有一致的变化。这个特征与1951～1999年的观测资料及模拟结果的EOF1十分相似。这表明代用资料能反映西部年降水量变化的主要特征。根据代用资料EOF1的时间系数及中心区降水量变化曲线,17世纪,特别是上半叶干旱严重。有资料证明,这个干旱期可能开始于16世纪70年代。近50年是400年以来中国西部年降水量最丰沛的时期。多雨主要发生在气候剧烈变暖的20世纪最后30年。从代用资料来看,降水量变化有“世纪周期”。17世纪的干旱与20世纪末的多雨是否分别与小冰期及现代气候变暖有关,还要进一步研究。

Climate change of annual precipitations in western China

Considerable long-term variability was found in precipitation changes in western Chi-na,where arid or semi-arid climate predominate.A set of17-site series of proxy precipitation da-ta was applied in this paper,among which11are tree ring series,4are historical data series and2are ice core series.The proxy data were normalized as following:the average of1880～1979was taken as normal,and percentage anomalies were calculated for each decade from the1600s(1600～1609)to the1990s(1990～1999).Finally,EOF analysis was carried out.The EOF1shows great concentration of the variance in Tarim Basin and north of Qilian Mountains.It is in good accordance with the characteristics of EOF1found in precipitation observations and simulations covering1951～1999.It proves to certain extent the reliability of the proxy data.The400-year se-ries of precipitation for western China shows significant dry period in the17th century,especial-ly in the first half of the century.An increasing of precipitation was found in the second half of the20th century,especially during the last30years.These dry period and the increasing of pre-cipitation may associate with the Little Ice Age and Modern Warming separately.Finally,"secular periodicity"was studied.It was manifested well in the deficits of precipitation in early period of each century.