1971-2010年青藏高原冬季降雪气候变化及空间分布

Climate change and spatial distribution of winter snowfall over the Tibetan Plateau during 1971-2010

利用青藏高原55个气象站1971-2011年冬季(12月-翌年2月)逐月降雪量资料分析了冬季降雪的气候特征,得到高原冬季降雪总体上呈现东部和南部多、西北部和雅鲁藏布江中段少雪的分布特征,相对变率分布与降雪的分布几乎相反且变率大,以30°N为界高原降雪存在南北反相的变化趋势即北部降雪有所增加而南部减少.用旋转经验正交函数REOF结合相关分析进行降雪分区的基础上,重点分析了近40 a来高原降雪的演变特征和长期气候趋势.结果表明:降雪分布清楚地反映了高原的地理特征和气候特点,即高原南部迎风坡、冷暖气流交汇处降雪多,而背风坡、北部降雪少;近40 a降雪呈现"少-多-少"趋势,1980-1990年代期间降雪明显偏多,大约1970年代中期发生了由少雪到多雪的突变现象,其中南部2个区分别在2007年和1988年出现了降雪减少的突变现象;降雪具有显著的准14 a年代际变化和准8 a周期变化,且存在年代际特征.

Monthly snowfall data in winter （ December to February） from 55 weather stations in the Tibetan Plateau from 1971 through 2011 were analyzed to reveal the variation characteristics of the winter snowfall over the plateau. The distribution of the winter snowfall over the Tibetan Plateau is characterized by more in the east and south and less in the northwest and the middle Brahmaputra. The distribution of the relative variability and the distribution of snowfall are almost on opposite, with large relative variability. Bounded by 30~ N, the plateau snowfall has opposite tendency between the north and the south. That is, snowfall increases in north and decreases in south. Based on the snowfall partition through applying rotated empirical orthogonal function, combined with correlation analysis, the evolution characteristics and long-term climate trend of the plateau snowfall during the last 40 years were analyzed. The following conclusions can be drawn： Snowfall distribution clearly reflects the geographical features and climatic characteristics of the Tibetan Plateau. That is, more snowfall in southern windward and the interchange zone of warm air and cold air, less snowfall in the leeward and north. During the last 40 years, the snowfall has shown from less to more, and then to less. It was significantly abundant from 1980 through 1990. An abrupt change from less snowfall to more had taken place in the mid-1970s. Mutation phenomena with snowfall reduction occurred respectively in 2007 and 1988 in two southern parts. Snowfall has significant periodic variations, a quasi-decadal variation （14 years） and a quasi-eight-year variation.