Possible Impacts of El Niño Events of Different Types and Intensity on Precipitation in the Subsequent First Rainy Season in South China

Based on the meteorological industry standard(QT/T370-2017)for El Niño events of different types and the latest monitoring standard of the first rainy season in South China issued by National Climate Center, using the NCEP/NCAR daily and monthly reanalysis data, NOAA SST data (ERSST V4), and the data collected at 261 meteorological observational stations in South China from 1961 to 2016, the relationship between El Niño events of different types and intensity and precipitation in the subsequent first rainy season in South China and the characteristics of the atmospheric circulation and SST are analyzed by correlation and composite analysis methods. The results show that the impacts of El Niño events of different types and intensity on the subsequent first rainy season in South China are obviously different. Under the influence of the East Pacific El Niño events with medium and higher intensity, the onset date of the first rainy season in South China is earlier than normal while the ending date is later than normal and the duration is longer with higher than normal precipitation. The opposite is true when South China is under the influence of East Pacific El Niño events with weak intensity or under the influence of central Pacific El Niño events. The atmospheric circulation in the first rainy season in South China under the influence of East Pacific El Niño events with medium and higher intensity is obvious different from that under the influence of weak East Pacific El Niño events or central Pacific El Niño events. In the former condition, the westerly jet in upper levels intensify, the polar vortex in the Northern Hemisphere and the East Asia major deep trough both become stronger than normal, an anomalous anticyclone develops to the east of the Philippines in the middle levels, and moisture convergence occurs in South China where southerly and northerly winds converge.