入冬以来最大一次降雪过程的多普勒雷达资料分析

Doppler Radar Data Analysis of the Largest Snow Process Since the Winter in Chengde of Hebei Province

[目的]分析2011年2月26日发生在承德市入冬以来最大的一次降雪天气过程的多普勒雷达回波演变特征。[方法]利用河北省承德市C波段多普勒雷达的反射率因子、径向速度、VWP产品,结合大尺度环流形势,对2011年2月26日发生在承德市入冬以来最大的一次降雪过程进行了分析,初步探讨了强降雪天气过程的多普勒雷达回波演变特征。[结果]降雪回波强度较弱,若有一定范围的30 dBz回波,且稳定少动,就有可能产生强降雪;暖平流加辐合、暖湿空气在低层浅薄的冷垫上爬升是这次降水形成的主要原因;"牛眼"结构的出现、低空急流的存在,为强降水的产生提供了源源不断的水汽;当垂直方向的风向发生改变且出现风速性辐散时,预示降水逐渐减弱并停止;暖平流与切变层的存在,是降水维持的重要原因。中层"ND"区域的出现、任意高度出现西北风预示着降水即将结束。[结论]该研究为强降雪的预报提供理论依据。

[Objective] Characteristics of Doppler radar data of the largest snow process since winter in Chengde City on February 26,2011 were discussed.[Method] By dint of reflection rate factors,radial velocity,and VWP product of Doppler radar in C wave in Chengde of Hebei Province,coupled with large scale of circulation situation,the largest snow process since the winter in Chengde City on February 26,2011 was discussed.[Result] The echo intensity of snow was weak.If there was certain rage of 30 dBz echo and was stable,there might be strong snow.The warm advection,convection and warm and wet air climbing over the thin cold cushion in the lower layer was the main reason of the precipitation.The structure of ＂cattle eye＂ and the torrent in the lower air provided incessant water vapor for the generation of strong precipitation.When the wind in the vertical direction changed there was wind speed divergence,it indicated that the precipitation weakened and stopped.The existence of warm advection and shear layer was the essential reason for the maintenance of precipitation.The ＂ND＂ area in the middle layer and the northwest wind at any height indicated the end of precipitation.[Conclusion] The study provided theoretical basis for the forecast of strong snow.