福建省一次强飑线过程的强度和移动特征分析

Motion and Intensity Characteristics of a Strong Squall Line Process Affecting Fujian Province

利用常规观测资料、区域自动站数据、雷达组合反射率因子以及NCEP GFS分析场资料(水平分辨率0.25°×0.25°),对2016年4月26日影响福建地区的一次强飑线过程的强度和移动特征进行分析。结果表明:此次飑线过程前期和后期的强度、结构、移动以及影响天气等方面存在显著差异。前期阶段,强的低层垂直风切变、对流层中层干冷空气卷入以及近地面辐合线的触发、低层切变线的动力抬升和低空急流的水汽输送是造成飑线进入福建境内强度显著加强的主要原因;后期阶段,减弱的飑线与西侧福建龙岩和粤北地区的新生单体合并形成后部扩建型飑线,位置停滞少动造成闽中地区大范围强降水。利用改进的移动矢量计算方法得到的向前传播型和后部扩建型飑线的移速和移向与实况基本吻合,在短时临近预报业务中具有实际应用价值。

Based on the conventional observation data, regional automatic station data, composite reflectivity factor of Doppler radar and NCEP GFS analysis field with 0.25°×0.25° spatial resolution, the intensity and motion characteristics of a strong squall line process affecting Fujian Province on 26 April 2016 were analyzed. The results show that the differences of intensity, structure, motion and induced weather were significant during the early stage and the late stage of the squall line process. During the early stage, the intensity of the squall line was strengthened by strong vertical wind shear in low level of troposphere and dry and cold air involvement in middle level. Furthermore, the triggering of ground convergence line, the dynamic lifting of low-level shear line and the vapour transportation of low-level jet were more favorable to development of the squall line. During the late stage, the intensity of the squall line weakened, and it merged and restructured as a back-building squall line with new convective cells in Longyan of Fujian Province and northern Guangdong Province, but the new system was quasi-stationary and caused a wide range heavy rainfall in the middle of Fujian Province. The improved vector technique of convective system motion can estimate the motion of forward-propagating and back-building squall line, and the results were basically matched with the observation, which can be a valuable reference in short-term forecasting and nowcasting of severe convective weather.