Major heavy rainfall events in China from April to October in 2021

Based on the daily precipitation data of 2, 424 stations and conventional weather chart data in mainland China in 2021, a statistical analysis of the main heavy rain weather processes from April to October of that year was conducted. The main influencing systems and precipitation situations were outlined, and a comparative analysis of the number of heavy rain days and major heavy rain events from 2008 to 2021 from April to October was performed. The results show that from April to October 2021, China experienced a total of 199 heavy rain days and 32 major heavy rain events. The number of heavy rain days was 10 days more than the average for the previous 13 years (2008-2020), while the number of major heavy rain events remained the same as the average for the previous 13 years. Among them, there were 7 occurrences in July, 6 in May and August each, 5 in June, 4 in September, and 3 in October, with 1 occurrence in April. Among the 32 major heavy rain events, 5 were caused by the landing or influence of tropical cyclones. The northern heavy rain from July 18th to 22nd, including the "7.20" extreme heavy rain in Zhengzhou, was the most widely affected and economically damaging major heavy rain event, with Zhengzhou in Henan Province recording the country's largest daily precipitation of 552.5 mm on July 20th of that year. The maximum accumulated rainfall for a single event in the year reached 820 mm, also occurring in Zhengzhou, Henan Province (July 18th to 22nd) and was caused by the joint influence of a trough, shear line, and warm and humid airflow.