According to “the Regulations on Monitoring and Evaluation of Regional Important Processes” issued by China Meteorological Administration in 2019, the basic situations of China’s climate and main meteorological disasters in summer 2021 are comprehensively analyzed based on the meteorological observation data of more than 2400 ground stations in China from 1961 to 2021. The results are as follows: (1) In the summer of 2021, both the average temperature and the average precipitation were higher than that in the same period of the previous years. The rainy season in the north started earlier with enhanced intensity, while it delayed in the south with weakened intensity. These two factors, together with the decreased number of landing typhoons, contributed to the fact that the summer precipitation zones dominated North China. (2) In the summer of 2021, China’s climate conditions were generally worse than normal, the situation of meteorological disasters was complicated and severe, accompanied with frequent occurrences of extreme weather and climate composite events, including flood, heat wave and drought, and moreover, the disasters exhibited periodic and regional features. The number of regional rainstorm processes was 4.9 times lower than that in previous summers, but the extremeness was much stronger. North China, Huanghuai, Jianghan and other places have suffered from severe rainstorms and floods consecutively. Regional high temperature occurred frequently and periodically. The number of regional high temperature processes was 3.4 times higher than that in previous summers, which mainly impacted Huanghai, Jiangnan, South China, the east of Northwest China, the west of Inner Mongolia and the south of Xinjiang. Meteorological droughts appeared in the south and the north simultaneously, with significant regional, periodic and compounding characteristics. And the number of regional drought processes was 1.1 times higher than that in previous summers. South China and Northwest China witnessed the compound development of high temperature and drought.

Based on hourly precipitation data from 96 meteorological stations during the flood season from 1980 to 2018 in Hunan Province, the occurrence frequency and contribution rate to the total precipitation amount were used as important indicators, and the spatialtemporal evolution characteristics of precipitation structure in Hunan Province during the flood season were analyzed. The results are as follows: (1) The occurrence frequency of rainfall events decreased by power function with increasing durations, while its contribution rate to the total precipitation amount of rainfall events increased linearly with increasing duration. The occurrence frequency of short duration rainfall event was high, while its contribution rate to the total precipitation amount was low. The occurrence frequency of long duration rainfall event was low, but contribution rate to the total precipitation amount was high and long duration rainfall event was the main body of precipitation in flood seasons. Both the occurrence frequency and contribution rate to the total precipitation amount of short duration rainfall events  were higher in southern Hunan than in northern Hunan, while the occurrence frequency and contribution rate to the total precipitation amount of long duration rainfall events were higher in northern Hunan than in southern Hunan. (2) In the past 10 years, both the occurrence frequency and contribution rate to the total precipitation amount of short duration rainfall events increased linearly, while the occurrence frequency and contribution rate to the total precipitation amount of long duration rainfall events decreased linearly. (3) Occurrence frequency of all rainfall events decreased by power function with increasing precipitation levels, while contribution rate to the total precipitation amount increased linearly with increasing precipitation levels. Although the occurrence frequency of torrential rainfall event was low, while it was the main contributor to precipitation during the flood season. The occurrence frequency and contribution rate to the total precipitation amount of light to moderate rainfall events were generally higher in southern Hunan than in northern Hunan, while the occurrence frequency and contribution rate to the total precipitation amount of heavy to torrential rainfall events were higher in northern Hunan than in southern Hunan.  (4) The interannual variation of occurrence frequency of light to heavy rainfall events was not significant, but the occurrence frequency of the torrential rain event increased significantly, while the interannual variation of contribution rate to the total precipitation amount of light rainfall events was not significant, but for moderate rain to heavy rainfall event it showed a significant downward trend, and contribution rate to the total precipitation amount of torrential rainfall events showed a significant upward trend.