渭河“2019.9”洪水特性及气象成因分析

Characteristics and meteorological causes of 2019. 9 Flood in Weihe River

为了进一步了解渭河秋汛洪水的特性及成因,利用2019年9月渭河洪水("2019.9"洪水)的流量、气象资料,对该次洪水的特性及持续性强降雨天气的成因进行分析。结果表明:此次持续性强降雨形成的原因是北半球极涡偏强,中纬度环流平直,同时副高位置相对稳定且异常偏西,导致冷暖空气持续交汇于渭河上空。过程期间水汽来自阿拉伯海和孟加拉湾,并在强降雨发生期间表现为水汽通量异常辐合。洪水主要来自渭河林家村—临潼区间的支流,其特点是含沙量小、干流较大流量持续时间长;临潼—华县区间的洪水演进缓慢、传播时间长、洪峰削减偏大。

In order to further understand the characteristics and causes of the autumn floods in Weihe River,this paper uses the flow and meteorological data of the flood happened in Weihe River in September,2019( 2019. 9 Flood) to analyze its characteristics and the meteorological causes of continuous heavy rainfall during the flood. The results show that the strong Arctic vortex in the northern hemisphere,flat circulation in the middle latitudes and relatively stable position and abnormally westward of the subtropical high pressure belt caused the continuous intersection between the cold and warm air over Weihe River,resulting in the continuous heavy rainfall. The water vapor of the rainfall came from the Arabian Sea and the Bay of Bengal,and the convergence of its flux appeared abnormal during the heavy rainfall. The flood mainly occurred in the tributaries between Linjiacun and Lintong with low sediment concentration,whereas heavy flow prevailed at the mainstream of Weihe River. The flood between Lintong and Huaxian proceeded slowly with long duration,and the flood peak was greatly reduced during the course.