Analysis of the basic characteristics and environmental conditions of sudden rainstorm processes in Pingxiang City from 2016 to 2023

Based on the precipitation data of 92 national and regional meteorological observation stations in Pingxiang City from 2016 to 2023 and the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis datasets (ERA-5), the synoptic characteristics of sudden rainstorms in Pingxiang City are investigated. The 1-hour, 3-hour, and 6-hour sudden rainstorm precipitation thresholds for each station are investigated in this study. The 1-hour, 3-hour, and 6-hour sudden rainstorm precipitation thresholds for each station are calculated using the percentile method. Five severe sudden rainstorm processes in Pingxiang City are identified according to the number of station times exceeding the thresholds. Meanwhile, the basic characteristics, circulation situation characteristics, and environmental field characteristics are comparatively analyzed. The results are as follows. (1) The five severe sudden rainstorm processes occurred on June 15, 2016, June 5, 2020, June 22, 2019, July 18, 2022, and July 23, 2023 (referred to as "2016.06.15", "2020.06.05", "2019.06.22", "2022.07.18", and "2023.07.23", respectively), and the main periods of heavy precipitation are concentrated in the early morning or morning. Compared with weak sudden rainstorms, severe sudden rainstorms have more stations where the 1-hour, 3-hour, and 6-hour precipitation amounts exceed historical extremes, and the maximum precipitation amounts in 1-hour, 3-hour, and 6-hour are also higher. Severe sudden rainstorms can maintain high precipitation intensity continuously for 3 or 6 hours. Moreover, the proportions of precipitation in 3 hours and 6 hours to the total precipitation exceed 48% and 77% respectively. (2) Four severe sudden rainstorm processes in Pingxiang City occur in the wind speed convergence zone of the low-level southwest jet stream. The occurrence and maintenance of the two severe sudden rainstorm processes on "2016.06.15" and "2020.06.05" were more significantly influenced by the upward transport following extreme water vapor convergence and the relatively strong vertical wind shear. The occurrence of the two severe sudden rainstorm processes on "2019.06.22" and "2022.07.18" mainly depended on the intense development of unstable atmospheric stratification and favorable energy conditions. (3) Only for the process on "2023.07.23", the conditions of water vapor convergence, dynamic lifting, and unstable stratification were all concentrated on the same isobaric surface at 700 hPa. This process exhibited relatively strong energy conditions and could simultaneously maintain moderate-intensity dynamic lifting conditions followed by water vapor convergence and moderate-intensity instability, thereby leading to the occurrence of sudden rainstorms. (4) Under the condition of similar upward transport intensity following water vapor convergence, the more unstable the atmospheric stratification, the stronger the short-term rainfall intensity during the severe sudden rainstorm process.