Abstract:To provide a reference for weather forecasting of major floods in the upper reaches of the Hanjiang River during autumn flood season, based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, we analyze the water regimen and rainfall characteristics, large-scale circulation characteristics, and causes for flood-causing rainstorm of major floods in the upper reaches of the Hanjiang River during autumn flood season since 2000. The results showed that the flood processes in the Hanjiang River Basin have gradually increased during autumn flood season since the 21st century. The flood-causing rainstorm center in autumn flood season is mainly located in the south and west of the upper reaches of the Hanjiang River, that is, the Micang Mountain and Daba Mountain in the south of the Hanjiang River Basin, the river valley in the upstream of the Ankang Reservoir, and the Danjiang River section at the southern foot of the Waifang Mountain and the westsouth slope of the Funiu Mountain. The peak of floods usually presents in the patterns of single peak, double peak or multiple peak. The duration of a single peak flood process is the shortest, while the duration of a multipeak flood process is the longest. The duration from the onset of maximum precipitation to the appearance of the flood peak is 43 h on average. When the initial inflow exceeds 4500 m3·s-1, the time required for the formation of the flood peak will be greatly shortened. From the perspective of large-scale circulation characteristics, the abnormal precipita-tion in the upper reaches of the Hanjiang River in autumn flood season is closely correlated to the strong blocking system in the mid-high latitudes over the Eurasia, the stronger and westward Western Pacific subtropical high, the northward South Asia high and subtropical westerly jet flow. The high-level divergence large-value area corresponds to the upper reaches of the Hanjiang River. The vertical motion from low to high levels is enhanced, which is conducive to the occurrence of flood-causing rainstorm. The water vapor transported northward from the Arabian Sea through the Indian Peninsula and the southern South China Sea and westward from the Western Pacific in autumn flood season flood year in the upper reaches of the Hanjiang River has increased abnormally, providing an unusually sufficient water vapor supply for the occurrence of flood-causing rainstorm.