利用常规观测、加密自动站观测和NCEP再分析资料，以及风廓线雷达、微波辐射计观测的精细风场、温度和湿度资料，对2009年11月9日夜间北京地区的一次回流暴雪天气过程的锋区特征进行了详细分析。结果表明，该过程的主要影响系统为华北锢囚锋和中高层短波槽，与锢囚锋联系的中低空暖湿空气在回流干冷空气上爬升造成锋生，是北京地区出现暴雪的主要原因。北京地区锋区的坡度较小，锋区下半层存在明显逆温。逆温强度可以指示冷暖交汇程度，从而与降雪强度存在相关关系，地形对逆温的分布和强度有一定的影响。低层东北风与中高层西南气流形成了明显的风垂直切变和温度差异，动力锋生机制发挥了重要作用，其产生的锋面次级环流直接促进了中尺度系统的发展。锋区存在层结不稳定，锋面抬升和次级环流促进了对流的发展，从而导致高架雷暴的产生。
Using conventional observations, satellite TBB, radar reflectivity, NCEP reanalysis data and unconventional observations including wind profile, automatic weather station and ground-based radiometer data, the characteristic of the occluded front of a backflow snowstorm in Beijing area on 9 November 2009 was studied. The result shows that: The slope of the front from north to south is gentle, the front in Beijing area is above 800 hPa, and the ∇θse and ∇T are serried vertically, the inversion (t/p) is strong. The warm moist air moves on the dry cold air which is the direct reason of the snowstorm. The lower level cold air becomes strong at the plain area because the block of the Taihang mountain, the intensity of the inversion can stand that of the front, the lower level Northeast airflow is dry and cold and it meets the warm moist air at the height of about 2000 m. The dynamical frontogenesis plays a very important role in the development of backflow snowstorm, the frontogenesis secondary circulation directly causes the snowstorm. There is unstable stratification in the front, the thunderstorm was triggered over the boundary level.
