Abstract:In order to reveal the weather causes of the rainstorm process that caused the flood in the Mintuo River and Jialing River basins, the rainfall and flood law of Yichang Control Station, and deepen the research on the occurrence and development mechanism of the flood in Yichang Station, based on the NCEP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)reanalysis data and the conventional meteorological and hydrological observation data, the flood characteristics of 19 flood causing rainstorm processes that occurred in the Mintuo River and Jialing River basins from 1980 to 2020 were analyzed and studied using statistical and synoptic methods Flood causing rainstorm source, rain belt characteristics, topography and weather system configuration, etc. The results show that: (1) Before the continuous rainstorm process starts, the initial inflow flow of Yichang, the main control station in the Yangtze River basin, needs to reach about 19000m3 · s-1, and the average time from the beginning of the continuous rainstorm process of Mintuo River or Jialing River to the peak flood is about 6 days. The duration of rainstorm and cumulative area rainfall have a good correspondence with the flood peak. Each flood generating process requires at least one rainstorm of more than 3 days, most of which are 4-6 days. (2) The entire flood process occurred from July to September. Mid July to mid August is the main month in Yichang where peak type floods occur most frequently, with 62% of the daily average flow of over 50000 cubic meters per second occurring during this period. (3) The process of flood causing rainstorm is dominated by quasi-static rain belt, followed by easterly type and turning type. 85% of the process rain bands are distributed in a northeast southwest direction. The central source of heavy precipitation is closely related to special terrain, mainly distributed in three places: the intersection of the lower reaches of the Minjiang River and the Qingyi River, where turning precipitation mostly occurs; The middle and lower reaches of the Jialing River, the Fujiang River basin, and the Qujiang River basin are mostly of quasi static type; 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. (4) The precipitation process is divided into two categories: quasi stationary persistent precipitation and mobile persistent precipitation. There are three types of weather conceptual models that are prone to major floods: Type I is the edge of the subtropical high in the Western Pacific. The westerly short wave moves eastward to trigger the rainstorm type. The subtropical high generally presents a north-south meridional type, often blocking in eastern Sichuan, forming a situation of "low in the west and high in the east". The short-wave low value system moving southward and eastward is blocked in the Mintuo River basin by the subtropical high, which is stable and less dynamic, and produces more quasi-static rain belts; Type II is the rainstorm type triggered by the eastward movement of the low value system of the Qinghai Tibet Plateau. The subtropical high is mostly distributed in the latitudinal direction. The multi low value system of the plateau is active, and the shear line is mostly transverse. The vortex is often formed in the west of the shear line, moving eastward along the shear line, which is easy to form mobile precipitation; Type III is a low-level easterly flow rainstorm type, with few precipitation processes, mostly occurring in August. In the north, the continental high pressure or the Western Pacific subtropical high cooperate. The Mintuo River and Jialing River are affected by the northeast flow at the bottom of the low pressure, with weak cold air infiltration. The tropical low-pressure system in the south is blocked for a long time and moves steadily westward. A strong easterly flow is easy to form between the two. Combined with special terrain areas, continuous heavy precipitation is very easy to produce and strengthen. (5) Nearly 70% of the processes involve tropical low value systems or typhoons, among which the existence of the Bay of Bengal tropical depression system is crucial to the continuous rainstorm in the upstream. Not only does it bring 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 eddies in the Mintuo River and Jialing River basins, combined with special terrain, resulting in strong upward motion.