青藏高原地区积雪年际变化异常中心的季节变化特征

利用青藏高原1980-2009年SMMR、SSM/I和AMSR-E被动微波遥感反演得到的逐日积雪深度资料, 应用EOF方法分析了近30 a青藏高原地区冬春季积雪年际变化异常的时空变化. 结果表明: 青藏高原冬春季积雪年际异常敏感区随季节有着显著变化, 并具有多尺度性. 其在大尺度上最主要的空间特征是从秋末(10-12月)到隆冬(12-翌年2月)位于青藏高原腹地和东南缘的河谷; 后冬和前春年际异常变化的敏感区显著变小, 整个青藏高原地区的积雪稳定少变; 而春季(3-5月), 随着青藏高原气温的回升, 敏感区出现在青藏高原东部. 青藏高原冬春季积雪年际变化在局地尺度上存在着季节变化, 表现为青藏高原积雪年际变化的异常与年际变化趋势相反的特征, 以及积雪年际变化东西反向异常随季节的演变. 青藏高原冬春季积雪年际变化的异常敏感区在空间范围上的变化, 反映了冬春季积雪在季节尺度上受冬季风和南来的暖湿气流之间相互消长和进退影响的特征. 青藏高原冬春季积雪具有显著的年代际变化, 在20世纪80年代处于多雪期, 80年代后期进入一个积雪较少期. 秋末至隆冬(10-翌年2月)的积雪在20世纪90年代后期出现明显转折, 进入多雪期, 2000年后又进入一个少雪期.

Seasonal characteristics of the interannual variations centre of the Tibetan Plateau snow cover

Using the snow depth data from satellite (SMMR, SSM/I and AMSR-E passive microwave remote sensing), the temporal-spatial variation characteristics of the Tibetan Plateau (TP) snow depth inter-annual anomalies were analyzed with EOF. There are remarkable seasonal and multi-scales characteristics of the inter-annual anomaly regions of the TP snow depth. In the period of late fall to mid-winter (from October to January), the inter-annual anomaly regions locate in the hinterland and valley. The area of anomaly regions become small, meanwhile, the snow depth on the TP is almost unchanged during late winter to early spring (from January to April). However, the anomaly regions of the TP snow locate on the eastern TP with the rising of temperature in spring (from March to May). There is a seasonal variation of the snow depth inter-annual anomaly center in the TP on the local scale, which shows the opposite change between the inter-annual anomaly and the trend of inter-annual anomaly in the TP snow depth. The change of the anomaly maximum region of the TP snow depth indicated the feature that the snow depth on the TP is influenced by winter monsoon and warm wet stream from the south. Further, the TP snow depth has an obvious inter-decadal variation. The snow depth is maximum during the 1980s, then decreased later, but the maximum snow depth from late autumn to winter (from October to February) occurs in 1990s. The TP snow amount was large in the late of 1990s, and decreased after 2000.