中文摘要：

利用中央气象台1951—2006年共56年冬半年（9月至次年5月）的冷空气天气过程资料、NCEP/NCAR逐日再分析海平面气压、500 hPa高度场和850 hPa气温等资料,统计分析了我国寒潮若干气候特征和寒潮中期过程的物理量场特征,并引入聚类方法划分寒潮典型物理过程。结果表明：（1）1951—2006年期间我国寒潮强冷空气逐年的活动频次呈明显下降趋势。功率谱周期分析表明,我国强冷空气活动有多年代际的变化周期。秋、冬、春季节是寒潮易发时节。（2）对我国寒潮天气过程特征物理量统计得到了一些表征寒潮天气特征量的阈值。寒潮冷高压强度有较明显的季节性变化特征,其源地大多可追溯到亚欧大陆北端极地,寒潮冷高压受山脉阻挡,在西伯利亚增强后最常以西北路径爆发南下,是我国寒潮最常见的路径。（3）乌拉尔山阻塞形势的崩溃与寒潮爆发密切相关;西风环流指数在寒潮爆发前6日前后至爆发后2日前后出现明显下降;在寒潮初始阶段,北半球高纬度以2波为主要特征,在寒潮爆发前,高纬度2波或3波为优势波的概率较大;北半球中纬度在寒潮中期过程主要为3波能量变化;北半球极涡面积迅速增大,与东亚＂倒Ω流型＂的建立紧密相关,是极地冷空气南下酝酿堆积的重要标志。

英文摘要：

Based on the cold wave activity data provided by China Central Meteorological Office and reanalysis data from NCEP/NCAR,the climatology and the physical characteristic of the cold wave activities in China from 1951 to 2006 are analyzed.The main conclusions are as follows：（1）The data analysis during the period of 1951 —2006 shows a decrease trend in the annual frequency of intense cold air and cold wave activities.A decade-scale cycle of the intense cold activities has been found by power spectrum analysis.The intense cold air and cold wave in China are likely to happen during changing seasons.（2）Some thresholds of the physical characteristic during the cold wave process have been calculated using the statistics analysis.The analysis of cold wave high indicates that there is an obvious seasonal change for the intensity of cold wave high.The cold wave high affecting China mostly traces back to the polar region in the north of Asia-Europe continent,the intensity of cold wave high is increased by the terrain factor.And the cold wave high usually affects China by north-west route.（3）The characteristic analysis during the cold wave process indicates： The collapse of the Ural blocking circulation has a close relationship with the cold wave outbreak;the westerly circulation index shows an obvious decrease during the 6 days,and before and after 2 days of the cold wave outbreak;the initial stages of the cold wave are characteristic of the peak value of the wave 2 in the high latitude,waves 2 or 3 are very likely to be the dominant wave in the high latitude before the cold wave outbreak,the energy change of the waves 3 is mostly distinct during the cold wave process in the middle latitude;the rapid increase of Northern Hemisphere polar vortex area closely relates to the establishment of the bottom up Ω circulation in the east Asia,and indicates the accumulation of the cold air from polar area.