Abstract:Based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, the meteorological and hydrological characteristics of the upper Yangtze River Basin during the severe flooding period from June to July 2018 are analyzed. The results show that three heavy precipitation processes occurred during the flooding period of the upper Yangtze River Basin in 2018, and the precipitation falling areas overlaped highly in the northern part of the upper Yangtze River Basin, causing serious disaster. Large scale circulation analysis shows that the low trough, subtropical high, Okhotsk blocking high and Ural blocking high in middle and high latitudes were stronger than those in the same period in records. The north south swing of subtropical high was larger. When the subtropical high jumped northward, it would encounter the cold air behind the trough in the upper Yangtze River Basin, forming a heavy precipitation process. The “saddle” configuration of large scale circulation facilitated the water vapor transport from the Bay of Bengal and the South China Sea to the upper Yangtze River Basin, and the convergence of water vapor in the region and the mid latitude westerly zone formed heavy precipitation. Compared with the historic records, we find that the precipitation in the upper Yangtze River Basin in 2018 was characterized by strong surface intensity, strong extreme precipitation in the northern tributaries and more concentrated raining period. Compared with the rainfall in 2012, the northern 〖JP2〗tributary of the upper〖JP〗 Yang tze River Basin had high water level and long time of exceeding the warning water level. The flood situation of Tuojiang River, Fujiang River and Jialing River was stronger than that of 2012. In 2018, the total precipitation and peak flow of the upper Yangtze River Basin did not exceed the situation in 2012, but the flood disasters caused by the Tuojiiang River, Fujiang River and Jialing River in the north of the upper Yangtze River Basin could exceed 2012.