广东一次飑线大风的成因和预警分析

Analysis of the Causation and Pre-warning of a Squall in Guangdong

利用NCEP/NCAR的1°×1°再分析资料、多普勒天气雷达和广东省自动站观测资料,对2016年4月13日发生在广东的一次飑线大风天气过程进行分析。结果表明:该次飑线具有强度大、生命史长和灾害影响大的特点。该次飑线过程发生前期,对流层低层伴有明显的暖平流,中高层出现冷平流,促进了该地区上空大气层结不稳定的形成和发展;中层西风的增强以及动量的下传,形成较强的垂直风切变,有利于风暴的的组织化和长时间的维持发展;在飑线移动发展过程中,地面风场中对应一条清晰的辐合线,对飑线的触发和维持起着重要的作用。雷达图分析表明该次飑线过程的弓形回波特征明显,移动速度快,反射率因子图上弓形回波前沿的反射率因子梯度大、强回波质心高和质心高度的急剧下降以及速度图上强的后侧入流、中层径向辐合等信息对大风的预警有明显的预示作用。降水粒子的拖曳作用和飑线的快速移动对地面大风的产生及增幅都有一定的作用。

With the NCEP/NCAR 1°×1° reanalysis, Doppler weather radars and automatic weather stations across Guangdong, we analyzed a squall weather process that happened in the province on April 13, 2016. The result is shown as follows. The squall was strong, lasted long and brought about great damage. In the early part of the process, there was obvious warm advection at the low level of the troposphere and cold advection at the middle and high level, advancing the formation and development of unstable atmospheric stratification over the region. Due to enhanced mid-level westerlies and downward transportation of momentum, a strong vertical wind shear occurred, being favorable for the organization and extended maintenance and development of the storm. During the movement and development of the squall, a corresponding well-cut convergence line appeared in the surface wind field, which played an important role in triggering and keep- ing the squall. As shown in radar echo analysis, the squall had well-defined characteristics of arc-shaped echo that moved fast. Large gradients of reflectivity factor, elevated height of the mass core of strong echo and its rapid decrease in altitude, strong rear-portion inflow and mid-level radial convergence are good indicators for the gale. The dragging effect of precipitating particles and rapid movement of the squall contributed in some way to the formation and enhancement of the surface gale.