Study of characteristic and rainstorm patterns classification of long-duration rainstorm in Panjin

Understanding rainstorm patterns is significant for the design of effective urban flood control and drainage systems. This study firstly analyzes the climatic characteristics of long-duration rainstorms (6~24 h) and conducts weather classification, and then long-duration rainstorms were rainstorm patterns classified using the fuzzy identification method and objective identification method. This analysis was based on the 1-minute interval rainfall data of Panjin observatory, daily surface and upper synoptic situations data of East Asia from 1972 to 2023. Lastly, the characteristics of rainstorm disasters were analyzed used disaster situation data from 1984 to 2023. The results showed that: (1) Long-duration rainstorms exhibited clear temporal variability, with fewer 3 events during the 1990s and most 7 events during 2010s and 1980s. The duration of long-duration rainstorms typically spanned between 6~10 hours, and the events of more than 18 hours were relatively rare. Long-duration rainstorms with precipitation between 90~110 mm were the most frequent. (2) The synoptic situations of long-duration rainstorms could be classified as the northward-moving cyclones with most proportion 42.3%, cold fronts with second proportion 20.4%, large cyclones with thirt proportion 28.7%, and Northeast cold vortexes with fewest proportion 8.6%. (3) The long-duration rainstorms in Panjin can be divided into seven types of rainstorm patterns with the unimodal rainstorms, uniform rainstorms and bimodal long-duration rainstorms accounting for 53.1%, 25.0% and 21.9% respectively. The peaks of the single-peak rainstorms were in the late and middle of rainstorm events, the peaks of the bimodal rainstorms were in the front and rear, in the front and middle of rainstorm events. (4) Analysis of disaster situation data and rainstorm patterns indicates single-peak in the middle and uniform long-duration rainstorms caused most severe waterlogging and flooding in Panjin, and thus should be paid special attention in future flood control and drainage planning.