欧亚大陆季节增（融）雪盖面积变化特征分析

利用美国冰雪资料中心(National Snow and Ice Data Center)提供的近40年逐周的卫星反演雪盖资料,定义了各季节新增(融化)雪盖而积指数(fresh snow extent),即增/融雪覆盖率P_(FSE)、增/融雪面积A_(FSE)、欧亚大陆北部增/融雪面积之和T_(FSE),针对欧亚大陆各季节平均的雪盖面积本身(snow extent,P_(SE)、A_(SE)、T_(SE)和其增(融)雪盖面积,分析比较二者的变化特征.结果表明,欧亚大陆各季节平均的雪盖面积和相应增(融)雪盖面积不论是气候态分布还是其年际、十年际变化均有明显不同,其中以冬、春季差别更为明显;夏、秋季二者虽有较好的一致性,但增(融)雪盖面积的变率明显强于雪盖而积本身;另外,冬季欧洲新增雪盖对欧业北部冬季雪盖面积以及其后的春季雪盖都有较显著的影响,而春季欧洲和中纬度亚洲地区的融雪则受到冬、春两季雪盖情况的影响.进一步分析欧亚大陆冬、春两季增(融)雪盖与ENSO关系显示,二者除在个别地区(两伯利业北部、欧洲中东部以及青藏高原)存在较明显关系外,整体上,欧亚大陆北部雪盖变化既不受控于ENSO,也不会显著影响ENSO.

Analyses of Seasonal Fresh Snow Extent over Northern Eurasia

Using weekly snow cover data(Version 3)during 1966-2005 from the National Snow and Ice Data Center,new indexes for the seasonal fresh snow extent are defined:Percent of fresh snow extent(P_(FSE)),area of fresh snow extent(A_(FSE))and total A_(FSE) over northern Eurasia(T_(FSE)).Then,the analyses are performed based on the new indexes and seasonal mean snow extent index(P_(SE),A_(SE),and T_(SE))to investigate the snow cover character-istics over Eurasia. The results show that the distinguished differences for the spatial distributions and temporal var-iations from Avsr.and A_(SE) are observed from seasonal to deeadal time scales,particularly in winter and spring.The variabilities of P_(FSE) are stronger than those of P_(SE) although their temporal and spatial distributions in summer and autumn are more consistent than in winter and spring.The winter A_(FSE) in Europe is found to have close relations with T_(FSE) and T_(SE) in winter and the subsequent spring,and the spring A_(FSE) in Europe and mid-latitude Asia is con-trolled by the snow cover status both in winter and spring.Further analysis indicates that the fresh snow extent in winter and spring is independent of ENSo in general,except for some small regions in northern Siberia,mid-eastern Europe and Tibet.