Characteristics and synoptic classification of short-duration heavy precipitation during the rainy season in Kunming based on regional station data

Short-duration heavy precipitation is a primary hazardous weather process during the rainy season in Kunming. Conducting an in-depth study of its spatiotemporal characteristics and synoptic systems is of great significance for enhancing local forecasting and warning capabilities for heavy precipitation. Based on hourly precipitation data from 12 national meteorological stations (referred to as national stations) and 406 regional meteorological stations (referred to as regional stations) in Kunming during May to October from 2018 to 2022, this study employed statistical and synoptic diagnostic methods, combined with subjective synoptic classification, to analyze the spatiotemporal distribution characteristics of short-duration heavy precipitation during the rainy season and performed circulation classification for regional processes. The results show that spatially, short-duration heavy precipitation exhibited a pattern of "more frequent in the south and less in the north," with the main urban area demonstrating a "rain island effect" characterized by the highest frequency and intensity. Temporally, its occurrence was most concentrated during the main flood season (June to August), with the peak of ordinary short-duration heavy precipitation in July, while the peak of extreme short-duration heavy precipitation was in June. The diurnal variation presents a bimodal structure, with primary peaks in the early morning and late afternoon. The main synoptic systems affecting regional short-duration heavy precipitation processes in Kunming can be classified into four types: shear line type (50.7%), tropical low-pressure system type (20.8%), two-high convergence type (17.4%), and subtropical high periphery type (11.1%). Differences in moisture source and topographic coupling, as well as the commonality of lifting trigger mechanisms, lead to differences in precipitation characteristics among different synoptic systems. The surface convergence line (or front) combined with the 700 hPa shear line is the key lifting trigger mechanism for short-duration heavy precipitation, providing valuable guidance for forecasting.