40-Year statistics of warm-season extreme hourly precipitation over North China

Abstract

North China (NC) is confronted with high risks of extreme precipitation events due to global warming and anthropogenic activities. Based on hourly gauge data from May to September during 1983–2022, this study investigates the distributions and trends of extreme hourly precipitation (EHP) and maximum hourly precipitation (MHP) in NC, and their linkages with elevation of stations. EHP is defined as the hourly precipitation exceeding the relative threshold (95th percentile). The results show that the threshold and EHP intensity increase from west to east, while the EHP amount rises from northwest to southeast. Overall, a significant increasing trend is observed in “station-mean” EHP amount in NC from 1983 to 2022, primarily driven by notable increase of EHP frequency. The distribution of EHP variables is closely correlated with elevation. Among the different terrain zones in NC, significant increases in EHP variables are observed both in plains (≤50 m) and mountains (>300 m). Notably, mountain stations show the most pronounced increase in EHP variables, with a noticeable rise in the probability of high-intensity EHP during the latter 20 years of the study period (2003–2022). Analysis of the anomalous circulation and long-term changes of circulation factors reveal that the westward leap expansion of the western Pacific subtropical high (WPSH), and significant increases in temperature and moisture are likely the direct causes of the overall increase of EHP and MHP in NC.