受两路冷空气共同影响下的铜仁暴雨特征分析

Analysis of Rainstorm Characteristics in Tongren under the Influence of Two Cold Air Channels

为了提升铜仁受两路冷空气共同影响时的暴雨落区预报准确性,根据自动站雨量观测资料、卫星观测资料、NCEP 1°×1°再分析资料、EC细网格风场资料,总结分析了铜仁受两路冷空气共同影响下的4次暴雨天气过程的降雨特征、环流系统演变、冷空气南下锢囚、系统垂直结构以及能量变化、EC的预报场等影响因素。通过分析发现,暴雨落区发生在铜仁西北部和东部的原因,一是由于湖北和四川两股冷空气南下进入贵州时,迫使地面暖空气抬升至重庆附近形成低压区,从而在铜仁西部和东部形成锋面,对流降水由锋面触发,二是受铜仁梵净山地形影响,近地层偏东气流遇山分流,在山的东侧形成辐合,山的西侧附近形成下沉或辐散,而山的北侧气流绕流与西北气流汇合,从而形成辐合降水;同时在地面锢囚低压上空,850 hPa层次重庆附近有暖湿低涡形成,暴雨落区跟低涡切变线的位置和低涡东侧偏东风大小有关系,较强的对流云团大多在低涡东南侧西南急流和切变线北侧东风急流里发展增强,EC模式较好的模拟预报出850 hPa低涡系统;另外暴雨发生前后伴有较强的CAPE的积累释放过程,对降雨的起止有一定的指示作用;较强的垂直上升速度区以及水汽通量散度辐合区均对降雨落区和强度有一定的指示意义。通过分析暴雨特征以及形成原因,能为类似暴雨过程的落区预报提供思路和要素参考。

In order to improve the forecast accuracy of the rainstorm area when Tongren is affected by the cold air from two channels,based on the automatic station rainfall observation data,satellite observation data,NCEP 1°×1°reanalysis data,and EC high resolution wind field data,the rainfall characteristics,evolution of the circulation system,southward confinement of the cold air,vertical structure of the system and the energy changes,the EC forecast field and other influencing factors of the 4 rainstorms in Tongren under the common influence of the cold air from two channels were summarized and analyzed.The results show the reason why the rainstorm occurred in the northwest and east of Tongren.First,when the two cold air from Hubei and Sichuan entered Guizhou southward,it forced the warm air to leave the ground,and form a low pressure area nearby Chongqing,thus forming a front in the west and east of Tongren,and triggered convective precipitation;Second,affected by the topography of Fanjing Mountain in Tongren,the easterly airflow in the near surface layer diverges by Fanjing Mountain,then forming convergence on the east side,sink or divergence near the west side of the mountain.the northwest airflow converged with airflow in north to form a convergent precipitation;At the same time,above occluded depression,a warm and humid low vortex is formed at the 850hPa near Chongqing.There was a well relationship between rainstorm area with the position of vortex shear line and the easterly wind on the east side of the vortex.The convective clouds mostly intensify in the southwest jet on the southeast side of the low vortex and the easterly jet on the north side of the shear line,the EC model predicts the 850hPa low vortex system well;In addition,There is a strong accumulation and release process of Cape before and after the rainstorm,which can indicate the beginning and end of rainfall;The strong vertical rising velocity area and the convergence area of water vapor flux divergence have a certain indication of rainfall area and intensity.By analyzing the characteristics and causes of rainstorms,it can provide ideas and element references for forecasting the areas of similar rainstorms.