Spatio-temporal distribution characteristics of precipitation processes in major urban agglomerations of China in recent 40 years

Based on the identification and evaluation method of hourly resolution precipitation processes, the annually and monthly variations of precipitation processes in different urban development stages were analyzed in seven major urban agglomerations of China, namely the Beijing-Tianjin-Hebei urban agglomeration, Yangtze river delta urban agglomeration, the Pearl River delta urban agglomeration, chengdu-chongqing urban agglomeration, Yangtze river middle reaches urban agglomeration, central plains city, and the guanzhong plain urban agglomeration. The hourly precipitation observation data from 1980 to 2019 were used in this study. The results showed: the frequency of precipitation processes in the seven urban agglomerations appeared an increasing trend especially after 2010; the frequency of precipitation processes was observed in winter and gradually increased from less to more; the hours of annual average precipitation increased, but the average process hours decreased; the durations of precipitation processes were increasing in March to April and August to September and decreasing in May to July; there were an increasing trend of the extreme + extra-strong + strong precipitation processes; the number of extreme and extra-strong precipitation processes increased significantly in August and September, while the strong precipitation process increased from March to June, and the heavy and medium-intensity precipitation processes increased in winter during the period of rapid urban development.