Abstract:Severe flood occurred in the middle and lower reaches of the Yangtze River Basin (MLYRB) in June-July 2020 (JJ2020). In this paper, the extreme features of the severe flood are analyzed based on the daily precipitation data from national stations since 1951 and the hourly observations from national and regional stations in JJ2020. The range of anomalous precipitation (anomaly percentage more than 50% or 100%) in MYLRB and the total amount are significantly larger than those in 1998 and 2016, ranked the second in recent 70 years following 1954. There are three rainfall large-value centers with maximal accumulated precipitation exceeding 1 500 mm, which refer to Dabie Mountain Area, southern Anhui and southwestern Hubei. The anomalous-precipitation-caused flood is closely related to the extreme long-term persistence of Meiyu in MLYRB. The Meiyu period in 2020 lasts for 52 days, 23 days more than the climatology. Moreover, in JJ2020, positive precipitation anomaly exists in each dekad, which has never been experienced before since 1961, reflecting the extreme features of the flood. The analysis of rain days of different grades shows that total stations having received moderate rain (10-24.9 mm·d-1), heavy rain (25-49.9 mm·d-1), torrential rain (50-99.9 mm·d-1) and severe torrential rain (≥ 100 mm·d-1) in JJ2020 are the most since 1961, especially the severe precipitations in the last three grades are more significant. The extremity of the severe precipitation can also be found in the short-duration heavy rain processes. In JJ2020, the accumulated station number and days with hourly precipitation over 20 mm and 50 mm are respectively 1612 and 100, both of which are the highest since 1981. At the four stations with total precipitation exceeding 1 500 mm, frequencies of hourly precipitation more than 20 mm are 2-4 times that of the same period in normal years. Accumulation of the first 43, 21, 19 and 27 heaviest hourly precipitation at the four stations exceeds their seasonal averages, respectively. The above results suggest that the significant extremity of the JJ2020 severe precipitation in Meiyu period in MLYRB exists in the total rainfall, the duration and the short-term intensity of severe precipitation.