Abstract:To reveal the weather causes of the rainstorm process that caused the heavy flood in the Mintuo River and Jialing River basins, the rainfall and flood law at Yichang Control Station, and to deepen the research on the occurrence and development mechanism of heavy flood at Yichang Station, based on the NCEP/NCAR reanalysis data and the conventional meteorological and hydrological observation data, this paper analyzes the characteristics of 19 flood-causing rainstorm processes that occurred in the Mintuo River and Jialing River basins from 1980 to 2020 by means of statistical and synoptic methods. At the sametime, the relationship between rainstorm and flood, flood-causing rainstorm source, underlying surface characteristics, and weather system configuration, etc. are also analyzed. The results show that as the main control station in the Yangtze River Basin, Yichang Station has an initial inflow of more than 19 000 m3·s-1 in the current period, and it just encounters a continuous rainstorm process, so the probability of major floods is greatly increased. The duration from the beginning of the continuous rainstorm process in Mintuo River or Jialing River to the flood peak is about 6 days on average. The rainstorm duration and accumulated area rainfall have a good corresponding relationship with the flood peak. The formation of each major flood requires a rainstorm process lasting more than 3 days, mostly 4-6 days. All of the flood processes occur from July to September. The process of flood-causing rainstorm is dominated by quasi-static rain belt, followed by easterly type and turning type. 89% of the process rain bands are distributed in a northeast-southwest direction. The central source of severe precipitation is closely related to special terrain, mainly distributed in three places: first, the intersection of the lower reaches of the Minjiang River and the Qingyi River, where turning precipitation mostly occurs; second, the middle and lower reaches of the Jia-ling River, the Fujiang River Basin, and the Qujiang River Basin are mostly of quasi-static type; third, in the middle reaches of the Fujiang River and the northern part of the Qujiang River Basin, the eastward moving rainstorm process often occurs here. The existence of the Bay of Bengal tropical depression system is critical to the continuous rainstorm in the upstream, followed by the low value system in the South China Sea, which accounts for 68% of the process. The depression system not only brings enough energy and water vapor to the Mintuo River and Jialing River basins, but the involvement of water vapor on its eastern side can easily trigger low vortexes in the Mintuo River and Jialing River basins, combined with special terrain, resulting in strong upward motion. The precipitation process is divided into two categories: quasi-static persistent precipitation and mobile persistent precipitation. There are three types of synoptic conceptual models that are prone to major floods. Type Ⅰ is rainstorm type triggered by westerly short-wave eastward movement at the edge of Western Pacific subtropical high. Type Ⅱ is the rainstorm type triggered by the eastward movement of the low value system of the Tibetan Plateau. Type Ⅲ is a low-level easterly air flow rainstorm type.