Winter and spring snow cover features in Beijing-Zhangjiakou Region

Beijing and Zhangjiakou will hold the 2022 Winter Olympics.For organizing a successful Winter Olympics, it is important to investigate the temporal and spatial variations of snow cover in the past decades, especial the most recent decade, using winter and spring snow-cover data from MODIS from 2002 to 2014, DEM and meteorological data from 1966 to 2013.It is found that snow cover ratio was low, with the maximum of 0.23, and appeared at the beginning of January, averaged from 2002 through 2013.The deposition of snow was slow, but snow melting was rapid; the distribution of snow cover was patchy.The fluctuation of snow days in winter was larger than that in spring; in February the number of snow days in Yanqing (4.6 days) and Chongli (13.9 days) was declining.Meanwhile the beginning and ending dates of snow cover were earlier than that before, while the duration of snow cover was shortened.There were two periods of relatively high snow depth, 1966-1980 and 2000-2012, but with distinct annual fluctuations.The pe