近50年青藏高原东部降雪的时空演变

选用1967-2012年青藏高原东部60个站点的观测资料,分析了该地区降雪的时空演变特征,并结合降水和气温的变化,探讨了降雪与积雪的关系,结果表明：青藏高原东部年降雪量在1.3~152.5 mm范围内变化,空间分布差异显著;秋季降雪表现出中间多、周边少的特征,冬季降雪表现出由东南向西北递减的特征,春季降雪最多且空间分布与年降雪基本一致;降雪可划分为青南高原区、藏北高原区、柴达木盆地区、青藏高原东南缘区、川西高原西北部区、青藏高原南缘区、青海东北部区及藏南谷地区;就青藏高原整体而言,除秋季外,整年、冬季和春季降雪均表现出“少—多—少”的年代际变化特征,其中冬季降雪在1986年发生了由少到多的突变,整年、冬季和春季降雪均在1997年发生了由多到少的突变;不同区域降雪的时间变化规律各具特点;降雪与积雪的关系十分密切,春季降雪受气温的影响最为显著,秋季次之,冬季最弱;20世纪末,春季降雪受气温升高的影响表现出与降水变化相反的由多到少的气候突变特征。

Temporal and spatial variations of snowfall in the east of Qinghai-Tibet Plateau in the last 50 years

Based on the data set of 60 weather stations in the east of Qinghai-Tibet Plateau for the period 1967-2012 and the methods of REOF, polynomial fitting, running t-test, the temporal and spatial variations of snowfall are analyzed. Meanwhile, combined with the variation of precipitation and air temperature, the relationship between snowfall and snow cover is discussed. The results indicate the spatial distribution of annual snowfall in the eastern Qinghai-Tibet Plateau is far from uniformity, varying in the range from 1.3 to 152.5 mm. The autumn snowfall is richer in the central part than in the surrounding area, the winter snowfall shows a gradual decreasing trend from southeast to northwest, the spring snowfall shows the same spatial distribution as the annual snowfall. Based on the REOF method, the field of snowfall could be classified into eight subregions: Southern Qinghai Plateau, Northern Tibet Plateau, Qaidam Basin, the southeast edge of Qinghai-Tibet Plateau, northwest of Western Sichuan Plateau, the south edge of Qinghai-Tibet Plateau, northeast of Qinghai Plateau and the valley in Southern Tibet Plateau. As a whole, in the eastern Qinghai-Tibet Plateau, except for autumn, the snowfall shows the obvious interdecadal change, namely, the snowfall was little before the mid-1980s, rich from the late 1980s to the late 1990s, and became little again after the end of the 20th century. By using running t-test method, winter snowfall shifted from the little stage to the rich stage in 1986, the snowfall in winter and spring shifted from the rich stage to the little stage in 1997. Also, in different subregions, the temporal variation of snowfall shows different characteristics. There is close relationship between snowfall and snow depth in the east of Qinghai-Tibet Plateau. The spring snowfall is influenced significantly by air temperature, followed by autumn and winter snowfall. Different from the shift of spring rainfall from the little stage to the rich stage at the end of 20th century, spring snowfall exhibited the shift from the rich stage to the little stage because of the rise of air temperature.