El Niño event has a significant impact on global climate, especially on regional droughts and floods, being an important source of signals for climate prediction. In order to understand the impact of El Niño on summer droughts and floods in North China, based on the monthly precipitation data of more than 2 400 stations from 1961 to 2022, the monthly sea surface temperature data reconstructed by NOAA and the reanalysis circulation data from NCEP/NCAR, this paper comprehensively studies the relationship between interannual variability of El Niño and summer droughts and floods in North China and its impact mechanism by using seasonal evolution empirical orthogonal function decomposition (SEOF), regression reconstruction of circulation anomalies, circulation composition analysis. The main results are as follows: (1) There is a significant negative correlation between the summer precipitation in North China and the El Niño state in summer of the current year. That is, El Niño begins to appear in the spring, develops in the summer and has a strong intensity, which results in less summer precipitation in North China and is prone to drought. Further analysis shows when the La Niña states in spring, summer, autumn and winter in the previous year change to El Niño states in spring, summer, autumn and winter in the current year, the summer precipitation in North China is significantly less and prone to drought. (2) El Niño affects summer precipitation in North China mainly by regulating the high and low level circulation. The circulation patterns of the 200, 500 and 850 hPa induced by El Niño in the summer of that year are consistent with the circulation patterns of the drought summer years in North China. (3) When the upper westerly jet at 200 hPa over North China and its north side is weak, the ascending motion caused by upper air disturbance will be obviously weak. The position of the western Pacific subtropical high at 500 hPa is southward, and North China is controlled by a circulation pattern of “high in the west and low in the east”. The low trough system moves eastward at a fast speed, which is not conducive to maintaining long-term precipitation processes in North China. The tropical Indian summer monsoon and the East Asian subtropical summer monsoon at 850 hPa are relatively weak, and North China lacks effective sources of water vapor transport. This high and low level circulation configuration will result in less precipitation in summer in North China, making it prone to drought.
