Abstract: An event of continuous rain weather occurred from late August to mid-October in 2017 in He'nan province;such weather occurred rarely in the past 14 years.The characteristics of atmospheric circulation during this event were analyzed based on meteorological data from 1961 to 2017 in He'nan province and the National Center for Environment Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data.Different analysis methods were used in this study,including the correlation analysis method,the T-test method,the wavelet analysis method,and the band-pass filter analysis method,etc.The results show that the Wular Ridge,the Bay Lake Trough,and the Western Pacific Subtropical High are abnormally strong and maintain for a long time during this event.Eastern Europe and Caspian-Bahu areas are the key upstream regions for the continuous rainy process.The atmospheric circulation in the Eastern Europe has an oscillation period from quasi two weeks to 30 days,while the oscillation period in the Caspian-Bahu is from 4 to 8 days.The east-west span of the 200-hPa jet axis and the maximum wind speed of the jet core are abnormally larger than that on average in the same period.The divergence zone in the southwestern part of the jet zone has the suction effect over He'nan province,which is conducive to the occurrence of precipitation.The zonal wind speeds of the upper jet enhance three times,corresponding to three continuous rainy processes.The water vapor transport sources and channels are different during different continuous rainy processes;water vapor in these three rainy processes originates from the Indian Ocean,the South China Sea,and the Western Pacific Ocean,respectively.

Key words: Blocking situation at mid-high latitudes, Low-frequency oscillation, Jet, Water vapor transport