摘要
In order to analyze the differences between the two snow cover data, the snow cover data of 884 meteorological stations in China from 1951 to 2005 are counted. The data include days of visual snow observation, snow depth, and snow cover durations, which vary according to different definitions of snow cover days. Two series of data, as defined by ＂snow depth＂ and by ＂weather obser- vation,＂ are investigated here. Our results show that there is no apparent difference between them in east China and the Xinjiang region, but in northeast China and the Tibetan Plateau the ＂weather observation＂ data vary by more than 10 days and the ＂snow depth＂ data vary by 0.4 cm. Especially in the Tibetan Plateau, there are at least 15 more days of＂weather observation＂ snow in most areas （sometimes more than 30 days）. There is an obvious difference in the snow cover data due to bimodal snowfall data in the Tibetan Plateau, which has peak snowfalls from September to October and from .April to May. At those times the temperature is too high for snow cover fol：mation mad only a few days have trace snow cover. Also, the characteristics and changing trends of snow cover are analyzed here based on the snow cover data of nine weather stations iri the northeast region of the Tibetan Plateau, by the Mann-KendaU test. The results show significantly fewer days of snow cover and shorter snow dtwations as defined by ＂snow depth＂ compared to that as defined by ＂weather observation.＂ Mann-Kendall tests of both series of snow cover durations show an abrupt change in 1987.
In order to analyze the differences between the two snow cover data, the snow cover data of 884 meteorological stations in China from 1951 to 2005 are counted. The data include days of visual snow observation, snow depth, and snow cover durations, which vary according to different definitions of snow cover days. Two series of data, as defined by ＂snow depth＂ and by ＂weather obser- vation,＂ are investigated here. Our results show that there is no apparent difference between them in east China and the Xinjiang region, but in northeast China and the Tibetan Plateau the ＂weather observation＂ data vary by more than 10 days and the ＂snow depth＂ data vary by 0.4 cm. Especially in the Tibetan Plateau, there are at least 15 more days of＂weather observation＂ snow in most areas （sometimes more than 30 days）. There is an obvious difference in the snow cover data due to bimodal snowfall data in the Tibetan Plateau, which has peak snowfalls from September to October and from .April to May. At those times the temperature is too high for snow cover fol：mation mad only a few days have trace snow cover. Also, the characteristics and changing trends of snow cover are analyzed here based on the snow cover data of nine weather stations iri the northeast region of the Tibetan Plateau, by the Mann-KendaU test. The results show significantly fewer days of snow cover and shorter snow dtwations as defined by ＂snow depth＂ compared to that as defined by ＂weather observation.＂ Mann-Kendall tests of both series of snow cover durations show an abrupt change in 1987.
基金
supported by the National Basic Research Program of China (2007CB411506)
the State Key Laboratory of Cryospheric Science (SKLCS08-06)
