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 (PFSE), area of fresh snow extent (AFSE) and total AFSE over northern Eurasia (TFSE). Then, the analyses are performed based on the new indexes and seasonal mean snow extent index (PSE, ASE, and TSE) to investigate the snow cover characteristics over Eurasia. The results show that the distinguished differences for the spatial distributions and temporal variations fromAFSE and ASE are observed from seasonal to decadal time scales, particularly in winter and spring. The variabilities of PFSE are stronger than those of PSE although their temporal and spatial distributions in summer and autumn are more consistent than in winter and spring. The winter AFSE in Europe is found to have close relations with TFSEand TSEin winter and the subsequent spring, and the spring AFSE in Europe and midlatitude Asia is controlled 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.