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.

How hailstorm occurrence will change in response to the warming climate is a hot topic, however the consensus regarding future projected changes is uncertain (Raupach et al., 2021;Seneviratne et al., 2012). This uncertainty results from the lack of uniform hail reporting to understand the present occurrence, and weaknesses in the physical linkage between hailstorms and the background atmospheric environment (

In many countries, thunderstorms are the main contributor to hourly extreme precipitation (HEP). Prior studies have shown that the number of thunderstorms decreased steadily in whole country of China, however, HEP increased significantly in several areas over the past half-century. The role of thunderstorms in changes in HEP occurrence remains largely unknown in China. In this study, for the first time, we used continuous 32-year records of hourly precipitation and thunder, and the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis, to analyze changes in thunderstorms under various vertical wind shear (VWS) environments, and their contribution to HEP occurrence. The number of HEP events associated with thunderstorms (TD-HEP) increased significantly in southern China (SC) but decreased significantly in northeastern China (NEC) and east of the Tibetan Plateau (ETP). Weak VWS thunderstorms accounted for 69.1% of TD-HEP in SC. Changes in the most unstable convective available potential energy and precipitable water (PW) in SC favored an increase in weak-VWS thunderstorms, which resulted in a 2.35 h warm-season−1 increase in overall “station-mean” TD-HEP events from 1980 to 2011. As the major contributor to HEP in NEC, moderate-VWS thunderstorms decreased by 0.37 h warm-season−1 due mainly to a reduction in PW, leading to a negative trend in TD-HEP events. Similarly, the decreasing TD-HEP occurrence on the ETP was due to a decrease of 1.12 h warm-season−1 of moderate-VWS thunderstorms. Studying the VWS environments of thunderstorms, and changes therein under a warming climate, can improve understanding of the changes in HEP in China.

Twenty-one runners died of hypothermia during the 100 km Ultramarathon Mountain race in Baiyin, Gansu Province on 22 May 2021. The hypothermia was caused by a combination of low temperatures, precipitation, and high winds associated with a typical large-scale cold front passing by the race site that morning. Based on historical hourly records of 13 meteorological surface stations over the past six years, temperature (3.0°C) and apparent temperature (−5.1°C) at 1200 LST as well as gust wind speed (11.2 m s −1 ) at 1100 LST on the day of the tragedy were found to be within the top or bottom 5th percentile for the month of May. The precipitation was only moderate at this time, but when temperature lower than 3.0°C, gust wind speed greater than 11.2 m s −1 , and precipitation greater than 0.1 mm for any adjacent three hours were combined together, 1200 LST 22 May fell within the top 0.1% of cases. The European Centre for Medium-range Weather Forecasting model produced reasonably good forecasts of the low temperature and high wind one day and seven days before the event, respectfully. Based on this study, lessons that can be learned from this tragedy are summarized from an academic perspective: Hazard and impact forecasts of high-impact weather events should be developed to increase the value of weather forecasts. Probability forecasts should be issued by government weather agencies and communicated well to the public. And more importantly, knowledge of how to evaluate the impact of weather should be delivered to the public in the future.We would like to extend our deepest condolences to the families and loved ones of the people who lost their lives in this tragedy, including 21 runners and one officer. May our efforts honor those who lost their lives by highlighting the value of weather forecasting and calling for greater action in the future.

Abstract. Insoluble particles affect weather and climate indirectly by heterogeneous freezing process. Current weather and climate models have large uncertainty in freezing process simulation due to little regarding species and number concentration of heterogeneous ice-nucleating particles, mainly insoluble particles. Here, for the first time, size distribution and species of insoluble particles are analyzed in 30 shells of 12 hailstones in China, using scanning electron microscopy and energy dispersive X-ray spectrometry. Total 289,461 insoluble particles are detected and grouped into 3 species: organics, dust, and bioprotein by machine learning methods. The size distribution of insoluble particles of each species vary greatly in different hailstorms but little in shells. Further, classic size distribution modes of organics and dust were performed as logarithmic normal distributions, which may be adapted in future weather and climate models though uncertainty still exists. Our finding suggests that physical properties of aerosols should be considered in model simulation on ice freezing process.