中文摘要：

基于华北农牧交错带冬季227个台站（1961-2012年）逐日降雪资料,采用多种统计诊断方法分析了冬季降雪的时空特征以及与环流因子的关系。结果表明：初冬降雪高值中心位于内蒙古东北部。在冬春之交时,降雪高值区移至华北南部。1960s和1970s为不同等级降雪的偏多时段,降雪的高值中心由内蒙西部（1960s）东移至河北、山西大部（1970s）。2000s以来大雪在山西、河北的北部地区最为显著,其次是呼伦贝尔地区。降雪频次的变化上可以发现,各区的大雪频次均呈减少趋势,其中Ⅵ区减少的趋势最为显著。在降雪偏少的时段（1980s、1990s）水汽输送较弱,呈西北—东南向;而在其他年代水汽输送较强,近10年水汽输送呈东南—西北向。在年代际上降雪总量与气温、AO指数呈反相关,而中等以上降雪量与气温和AO指数在内蒙古东北部大兴安岭、太行山脉等高海拔地区呈显著正相关。

英文摘要：

Using daily snowfall observations （1961-2012） of 227 meteorological observation stations which are treated by a series of climatic statistical methods, analysis is performed on the temporal and spatial characteristics of winter snowfall in the agri-pasture transitional zone of North China and its relations with circulation factors. The result shows that the high value center of snowfall is located in the northeast of Inner Mongolia in early winter, and then it moves to the southern part of North China at the end of winter and the beginning of spring. The periods of the 1960s and 1970s witnessed more snowfalls at all levels than normal, with high value centers moving eastward from West Inner Mongolia （in the 1960s） to most parts of Hebei and Shanxi provinces （in the 1970s）. Since the 2000s, heavy snowfalls across North China have been the most significant in the north of Shanxi and Hebei provinces, with Hulunbuir coming next. Regarding variations of snowfall frequencies, there is a decline in the frequency of heavy snowfalls in different regions, with the most significant decrease occurring in Hebei province and the south of Shanxi province （named as the VI region in this paper）. During the period with fewer snowfalls in North China （in the 1980s and 1990s）, vapor transport was weak, moving from northwest to southeast; whereas during the years of strong vapor transport, the water transport in the past decade moved from southeast to northwest. The inter-decadal snowfall has a negative correlation with the air temperature and Arctic Oscillation （AO） index, whereas the snowfall at moderate and high levels is positively correlated with the air temperature and AO index in high latitude areas like the Greater Hinggan and Taihang Mountains in northeastem Inner Mongolia.