Changes in Hourly Extreme Precipitation Over Eastern China From 1970 to 2019 Dominated by Synoptic‐Scale Precipitation

Because of its dense population, extreme precipitation, in particular hourly extreme precipitation (HEP), is receiving increasing attention from both academic and public bodies in eastern China. Based on a continuous 50‐year record of hourly precipitation and reanalysis data, we show here for the first time that changes in the HEP occurrence are dominated by changes in the duration of the Meiyu front system. Further analyses reveal that greater occurrence of HEP in northeastern China, the lower reach of Yangtze River, and southern China during the warm season is largely due to a longer duration of the post‐Meiyu I stage when Meiyu front stays in northern China and meridional circulation dominates the eastern coastal area of China. These results improve our understanding of the changing behavior of extreme rainfall in China and shed light on the prevention of flash floods. Plain Language Summary Hourly extreme precipitation (HEP) events can lead to instant disasters, such as flash floods or waterlogging, resulting in huge losses of human life and property in a short period. Most previous studies have focused on daily extreme precipitation in China. Our study examined how and why HEP has changed in the past half‐century. We show that changes in the number of HEP events are mainly contributed by synoptic‐scale extreme precipitation in the warm season over eastern China. Furthermore, as the Meiyu front stays longer over northern China in recent years, the number of HEP events have increased in July and August in the lower reach of Yangtze River, northeastern and southern China. These results improve understanding of the response of HEP to climate change and imply that synoptic weather systems might be more important for changes in the occurrence of HEP than local‐scale weather systems. Key Points The number of hourly extreme precipitation (HEP) events has increased in the lower reach of the Yangtze River, northeastern and southern China These increases mainly occur in the post‐Meiyu I stage when southerly winds dominate eastern China; Meiyu front stays in northern China The extended duration of the post‐Meiyu I stage contributes to the increase in HEP