内蒙古锡林郭勒盟2012年冬季暴雪过程天气学特征研究

暴雪是冬季雪灾发生的主因，气候变化导致极端天气气候事件频繁发生，准确预报暴雪天气过程对防灾减灾起着重要作用. 以内蒙古锡林郭勒盟地区2012年11月3-5日出现的一次暴雪天气过程为例，对2012年锡林郭勒盟地区冬季出现的暴雪天气过程进行了诊断分析. 结果表明：暴雪天气过程的主要环流背景条件是乌拉尔山长脊和西伯利亚冷涡，而高空蒙古低槽、低空切变线和地面河套气旋是这次暴雪的触发机制. 此次暴雪天气属于强冷空气类蒙古低槽(涡)型，发生在高湿区和水汽通量辐合区内，地面气旋和华北脊对暴雪的产生和落区起到决定性作用. 暴雪天气从降雪前期到结束，整层湿层较深厚，低空急流的建立为暴雪提供了很好的不稳定能量和水汽辐合条件，锡林郭勒盟地区有高空辐散低空辐合强烈的上升运动，为此次暴雪提供了非常有利的动力条件. 乌拉尔山高压脊东移，使强冷空气沿脊前西北气流南下，地面气旋不断发展，而南方暖湿气流强盛，迫使气旋东移；华北脊的阻挡作用使得气旋缓慢移动，影响系统滞留于锡林郭勒盟地区，产生长时间的降雪天气.

The Synoptic Characteristics of a Snowstorm During Winter of 2012 in Xilingol League,Inner Mongolia

Using conventional observation and automatic weather station data, the snowstorm weather process in November 3-5, 2012, in Xilingol League was diagnostically analyzed. It is found that the snowstorm is confined by a stable planetary scale weather system, and controlled by the low level shear line together with Hetao cyclone. The storm was a strong cold air in Mongolia trough (vortex) in high humidity and water vapor flux convergence region. Surface cyclone and North China Ridge had a decisive action to the snowstorm. Dynamic condition of the snowstorm had some different from synoptic model of heavy snow weather or blizzard weather in Inner Mongolia. One can see that there was no upper level jet stream. A low level jet with strong water vapor convergence and unstable energy condition provided beneficial condition to the snowstorm. The high-and low-level jets coupling was not obvious, but from the physical quantity analysis of vorticity and divergence in Xilingol League, it is found that there was strong ascending motion of upper air divergence with low-level convergence, which provided dynamic condition favorable to the snowstorm.