山东中西部一次超级单体分裂过程的雷达回波结构和环境条件分析

Analysis of Environmental Conditions and the Structure of Radar Echo for a Supercell Splitting Process in the Midwestern Shandong Province

利用常规观测资料、济南多普勒雷达资料、FY-2G资料和加密自动站等资料分析了2016年6月14日一次在华北冷涡背景下发生的超级单体风暴生成及分裂过程,对超级单体分裂过程的雷达回波特征和环境条件进行了详细的分析。结果表明,超级单体风暴发生在地面中尺度辐合线附近,中层短波槽前,高空有中空急流的环境下,触发的对流云团向偏东方向移动中,在不稳定层结和较强的垂直风切变作用下,对流风暴发生分裂且右移性对流风暴发展加强。风暴分裂后环境风左侧的风暴单体并没有受到明显抑制,中尺度辐合线附近的露点锋生抵消了反气旋性风暴的受抑制程度,使反气旋性风暴能有所加强并持续更长的时间。环境风右侧的风暴单体发展加强,且持续时间长达2 h。风暴分裂是在单体发展的初期开始,分裂先从中高层开始,然后向下延伸,分裂后相对于环境风方向,左侧单体为反气旋性左移风暴,右侧为气旋性右移风暴。气旋性右移风暴强烈发展为具有低层的入流缺口、中高层的弱回波区及风暴顶的强辐散,与经典超级单体风暴回波特征类似。分裂后右移风暴伴有深厚持久的中气旋,其起源于中层4~5 km,然后向上和向下发展,最强旋转出现在高层,旋转速度达29 m/s,这与典型超级单体内中气旋都是中层旋转最强有所不同。

Based on conventional observation data,in this study,we analyzed Jinan Doppler weather radar data,FY-2G data,and automatic weather station data with respect to the formation and splitting processes of a supercell storm that occurred in the background of a cold vortex in North China on June 14,2016.The radar echo characteristics and environmental conditions of the splitting supercell were analyzed in particular detail.The results showed that the supercell storm occurred near the mesoscale convergence line on the ground,in front of the centrally located short-wave slot trough.In an environmental condition characterized by hollow jets at high altitudes,which triggered an easterly moving convective cloud cluster,unstable layers,and strong vertical wind shear,the convective storms split,with those that were right-shifting strengthening.After splitting,the storm monomer on the left side of the environmental wind was not significantly restrained.The dew-point front near the mesoscale convergence line offset the resistance of the anticyclonic storm,which strengthened and extended the life of the anticyclonic storm.The storm monomer on the right side of the environmental wind was strengthened and lasted 2 h.The storm splitting process began at the initial stage of monomer formation,with the split initiating at the middle and upper levels and then extending downward.After the division,relative to the direction of the environmental wind,the left monomer was an anticyclonic leftward-moving storm,and the right monomer was a cyclonic rightward-moving storm.The cyclonic rightward-moving storm featured an inflow notch at the low level,a bounded weak echo region at the middle-upper level,and strong storm-top divergence at the upper level.These echo features are similar to those of a classic supercell storm.After the division,the rightward-moving storm was accompanied by a deep and long-lasting mid-cyclone that had originated at the middle level(four to five kilometers),and then developed both upward and downward.Its strongest rotation occurred at a high level with a rotation speed of 29 m/s.This differs from the behavior of the classic supercell monomer,which has its strongest rotation in the middle level.