一次热带低压伴随中尺度锋生的暴雨天气过程分析

利用地面观测资料和NCEP/FNL再分析资料，对福建省东北部2018年8月24—25日热带低压影响下的暴雨天气过程进行分析，以揭示中尺度锋生对局地强降水的作用。结果表明：此次暴雨天气过程具有降水集中、局地性强、强度大、持续时间长、存在2个明显降水阶段的特征。强降水过程伴随中尺度锋生现象，且在第二阶段明显强于第一阶段，为第二阶段强降水提供有利动热力条件。热带低压移动缓慢，降雨持续时间长，配合中纬度槽带来的弱冷空气，是此次极端降水的原因之一。2个降水阶段都有较好的水汽供应，第二降水阶段水汽通量弱于第一阶段，说明水汽供应不是造成2个阶段降水强度差异的主要原因。由于低层风速较大，地形抬升比水汽供应具有更重要的作用。

Analysis of An Extreme Rainstorm Caused by Tropical Depression Associated with Mesoscale Frontogenesis

Based on the surface automatic observation data and NCEP/FNL reanalysis data, an extreme rainstorm caused by tropical depression in northeast Fujian province from 24 to 25 August 2018 was analyzed to reveal the role of mesoscale frontogenesis in local heavy rainfall. The results showed that the process presented the characteristics of concentrated precipitation, strong locality, large intensity, long duration and two obvious precipitation stages. The process of heavy rainfall was accompanied by mesoscale frontogenesis, which was significantly stronger in the second stage than in the first stage, providing favorable dynamic and thermal conditions for the second stage of heavy rainfall. The slow movement of the tropical depression and the long duration of rainfall, combined with the weak cold air brought by the mid latitude trough, caused the extreme rainfall. There was good water vapor supply in both precipitation stages, and the water vapor flux in the second precipitation stage was weaker than that in the first stage, indicating that the water vapor supply was not the main reason for the difference in precipitation intensity between the two stages. Due to the high wind speed in the lower layer, terrain uplift played a more important role than water vapor supply.