Characteristics of Moisture Transport in Rainstorms in Different Regions of Eastern China under the Background of Warm-season Northeast Cold Vortex

This study uses reanalysis data, surface observations, and a Lagrangian trajectory model to compare the characteristics and moisture transport mechanisms of cold vortex and non-cold vortex rainstorms in Northeast China, North China, and the Jianghuai region under the influence of the Northeast Cold Vortex. The results show that: (1) The high-value area of rainstorms in Northeast China is located along the southern coast; in North China, it is in the southeast, with non-cold vortex rainstorms being more intense; in the Jianghuai region, cold vortex rainstorms are distributed along the Yangtze River, while non-cold vortex rainstorms are concentrated in the central-north and southeastern coast. Rainstorm frequency peaks in July in Northeast and North China, and in June in the Jianghuai region. The cold vortex significantly changes the rainstorm distribution in the Jianghuai region in June and August. All three regions show an upward trend in cold vortex rainstorm frequency, with the fastest increase in the Jianghuai region. (2) For cold vortex rainstorms in Northeast China, the southwest pathway contributes the most (40%), while non-cold vortex rainstorms are dominated by the southeast pathway (48%). In North China, both cold vortex and non-cold vortex rainstorms are primarily influenced by the southwest pathway (45% and 42%, respectively). In the Jianghuai region, the southeast pathway accounts for 62% of cold vortex rainstorms, compared to 46% for non-cold vortex rainstorms. (3) In Northeast China, the cold vortex easily triggers strong local cyclonic convergence, with moisture mainly from the eastern coast. In North China, the cold vortex introduces dry and cold air during rainstorms, reducing moisture but enhancing dynamic uplift through north-south wind convergence. In the Jianghuai region, the southward shift of the cold vortex interacts with the western Pacific subtropical high, leading to collisions between dry easterly currents and warm moist southwesterly jets, triggering convective instability and intensified precipitation.