Analysis of temporal and spatial characteristics of extreme hourly precipitation in the warm season in the Qinhe River Basin in recent 20 years

Based on the hourly precipitation observation data from 10 national meteorological stations in the Qin River basin of the middle reaches of the Yellow River during the warm season (May-September) from 2004 to 2023, the spatio-temporal characteristics of extreme hourly precipitation in the Qin River basin during the warm season were analyzed. To verify the representativeness of the national meteorological station data, the analyzed spatio-temporal variation characteristics were compared with the conclusions drawn from data analysis utilizing information from 96 Provincial meteorological stations from 2018 to 2023. The results are as follows. (1) The spatial distribution characteristics of extreme hourly precipitation threshold, intensity, annual average frequency and contribution to precipitation in warm season are lower in the middle and upper reaches than in the lower reaches. However, the trends in changes in precipitation intensity, frequency, and contribution rates are not significant. (2) The monthly variation presents a unimodal pattern, with the highest frequency and intensity of extreme hourly precipitation occurring in July. The diurnal variation distribution presents a bimodal pattern, with the highest frequency occurring at 09:00 BT and 13:00 BT, and the lowest frequency occurring at 01:00 BT. There is little difference in the intensity of daytime and nighttime rainfall. The proportion of extreme hourly heavy precipitation events with intensities above 50 mm·h⁻¹, Extreme hourly heavy precipitation exceeding 50 mm·h⁻¹ occurs from June to August, The highest frequency of occurrence in July, and the most occurrences at 05:00 BT and 07:00 BT. (3) The spatial distribution of extreme hourly precipitation thresholds, intensity, and contribution rates, as well as the diurnal variation characteristics of precipitation, based on the analysis of data from Provincial meteorological stations in the Qinhe River basin, are consistent with those derived from national meteorological station data. However, for extreme hourly heavy precipitation peaks above 50 mm·h⁻¹ , there are differences in the time periods when the peak precipitation occurs between the two datasets. Nevertheless, the monthly and diurnal trends exhibited by both datasets remain consistent.Therefore, the analysis results based on the long-term series of national station data are credible and representative, providing a reference for extreme hourly precipitation forecasting and warning, basin climate analysis, climate feasibility studies, and other related work in the Qinhe River basin.