河北承德地区一次暴雨过程数值模拟和诊断分析

摘要

Based on hourly meteorological data from automatic weather station,TBB data,Doppler radar data and NCEP 1°×1°reanalysis data,a rainstorm process on July 24 to 25,2011 in Chengde of Hebei province was ana-lyzed.A mesoscale numerical model WRF (Weather Research and Forecast)was used to simulate this process. The results show that there is a wind convergent center according to measured wind field data from automatic weather stations,and the TBB of mesoscale convective cloud clusters is less than -60 ℃ in this rainstorm process. On the radar chart,a thread type strong echo in red color with a central intensity up to 50 dBz embeds in a strong sheet echo and moves with main body echoes during a long time.Velocity field configurations of warm advection and wind convergence as well as high and low level jets are the main reasons causing the heavy rainstorm in Chengde of Hebei province.According to water vapor flux divergence distribution simulated using the WRF mod-el,it can be seen that strong convergence and aggregation of low-level moisture provide abundant moisture for this process.Pumping action leads to the development of vertical movement when divergence in upper level is stronger than convergence in lower level,thus a lot of water vapor is transported from lower level to upper level,which pro-motes the formation and maintenance of heavy rainfall.%利用逐小时自动站资料、TBB 资料、多普勒雷达资料和 NCEP 1°×1°再分析资料对2011年7月24—25日河北承德地区一次暴雨天气过程进行分析，并利用高分辨率中尺度数值模式 WRF 对此次暴雨过程进行了数值模拟。结果表明：此次河北承德地区暴雨天气过程地面自动站风场存在辐合中心，中尺度对流云团云顶 TBB ＜－60℃。雷达回波中心强度≥50 dBz的红色线状强回波镶嵌在较强的片状回波中，并长时间随着回波主体移动；暖平流与风场辐合迭加的速度场配置及高低空急流的存在，是河北承德地区此次大暴雨产生的主要原因。WRF 模式模拟了此次承德地区降水的水汽通量散度分布，低层水汽强烈辐合和聚集，为暴雨的产生提供了充沛的水汽；高层辐散大于低层辐合，抽吸作用使垂直运动发展，大量水汽从低层向高层输送，促进强降雨的形成和维持。