2014年2号热带低压导致福建闽西北灾害成因分析

摘要

In August,2014,No.2 tropical depression (TD2)moves northward after landing in Xiapu Coun-ty,Fujian Province.It results in an extremely heavy rainstorm in northwestern Fujian Province and the related flood and geological disasters.These disasters affect nearly 100,000 people with 4 people dead,and cause an economic loss of 250 million RMB.Great discrepancies in terms of the intensity and location of this rainstorm are found a-mong different numerical prediction models (NWPs).To analyze this extremely heavy rainstorm process,various data including automatic meteorological station,radar products,and routine weather map are used.It is shown that this rainstorm is attributed to the interactions between northward-movement TD2 arising from the South China Sea and cold air from high latitudes.The rainstorm originates from this type of weather background:eastward migration of high-level trough,wind shear in middle-low levels,southward movements of cold front,and northward move-ments of TD2 in the South China Sea.After landing in Fujian,the maintenance of TD2 intensity is due to the incor-porations of the moist baroclinic frontal zone related to the cold air,positive vorticity area near the wind shear in middle-low levels,and high divergence area before high-level trough and to the right of the southwesterly jet. Northward-movement TD2 provides a great amount of water vapor with high energy and high temperature.Through interacting with the cold air,unstable condition and ascending motion intensify,which further triggers the convec-tion.Since the cloud clusters of the TD2 and the westerly trough merge in Northwestern Fujian Province,a more powerful cloud cluster is formed.The location of the extremely heavy rainstorm is in good accordance with the area of moist baroclinic front,convective unstable zone,overlapping area of positive moist potential vorticity in high lev-el and negative moist potential vorticity in low level,and ascending motion zone.%2014年8月19日，南海热带低压在福建漳浦沿海登陆后北上，造成福建闽西北大暴雨并引发洪涝地质灾害，受灾人口近10万人，因滑坡死亡4人，直接经济损失2.5亿元。各种数值预报模式对这场暴雨强度和落区的预报都有较大误差。利用自动站加密观测资料、雷达产品、常规天气图对这场大暴雨过程进行分析，结果表明，南海热带低压登陆北上后与冷空气共同作用造成了此次大暴雨。大暴雨是在高空槽东移、中低层切变、锋面南压和南海热带低压北上天气背景下产生。热带低压登陆福建后靠近冷空气带来的湿斜压锋区、中低层切变附近的正涡度区和高空槽前西南急流轴之右侧的高空辐散区，强度得到维持。热带低压北上为暴雨区上空输送了大量高能高湿的水汽，并与南下冷空气相互作用，不稳定条件和上升运动明显加剧，触发了对流的发展。南海热带低压云团与西风槽前对流云团在闽西北上空合并，对流云团获得进一步发展。大暴雨落区与湿斜压锋区、对流不稳定区、高低层正负湿位涡叠加区和垂直上升区有很好的对应关系。