Spatiotemporal characteristics of short-time heavy rainfall in relation to topography in western Guanzhong, Shaanxi Province

Investigating the spatiotemporal characteristics of short-time heavy rainfall and its relationship with topography is crucial for developing regionally refined nowcasting models and enhancing risk assessment and prevention capabilities for extreme precipitation disasters. The spatiotemporal distribution of short-time heavy rainfall in western Guanzhong was analyzed using hourly precipitation data from 327 meteorological stations during the warm season (April-September) from 2018 to 2024, ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts, and 30 m digital elevation model data. The controlling roles of topography were investigated using inverse distance weighting, principal component analysis, and linear regression. The results indicate the following: (1) The frequency of short-time heavy rainfall events during the warm season increased between 2018 and 2024. The rainfall intensity predominantly ranged from 20 to 40 mm·h−1. The majority of events occurred between mid-July and early August, and the maximum recorded rainfall intensity exceeded 50 mm·h−1. The diurnal variation was bimodal, with the most active period between 18:00 and 23:00. (2) The spatial distribution was uneven: high-frequency rainfall areas were located in the northern high-altitude loess tableland and the northern foothills of the western Qinling Mountains, and low-frequency rainfall areas were located in the eastern low-altitude plains. Significant diurnal variation was observed. During the daytime, high-frequency areas were scattered primarily north of the Weihe River, whereas during the night they were concentrated on the northern loess tableland. (3) The frequency of the short-time heavy rainfall was significantly correlated with elevation, latitude, and longitude, with elevation the most dominant factor. Topographic thermal uplift played a secondary role, and dynamic lifting had the least influence. The short-time heavy rainfall showed a single-peak pattern with altitude, with most events occurring at altitudes between 400 and 1300 m. The frequency of short-time heavy rainfall above 1300 m decreased with increasing altitude. These findings provide a theoretical foundation for improving forecasting and the early warning of short-time heavy rainfall in the region.