Interdecadal Variation of the Relationship between Summer Precipitation in the Beijing-Tianjin-Hebei Region and ENSO

The El Nino-Southern Oscillation (ENSO) represents the most prominent interannual signal within the global ocean-atmosphere system and stands as one of the crucial factors influencing the interannual variability of summer precipitation in the Beijing-Tianjin-Hebei Region. Based on data such as spring sea surface temperature, summer precipitation in the Beijing-Tianjin-Hebei region, and atmospheric circulation from 1961 to 2023, this study analyzes the interdecadal variation in the relationship between spring ENSO and summer precipitation in the Beijing-Tianjin-Hebei region, as well as its possible causes. The results show that the key spring ENSO region, which has a significant impact on the interannual anomalies of summer precipitation in the Beijing-Tianjin-Hebei region, underwent an interdecadal shift in the late 1990s, changing from the eastern Pacific in the earlier period to the central Pacific in the later period. Although the SSTAs(sea surface temperature anomalies) in the key spring ENSO region before and after the shift both exhibit a strong negative correlation with the summer precipitation anomalies in the Beijing-Tianjin-Hebei region, the underlying mechanisms are significantly different. When there are anomalies in the sea surface temperature of the key spring ENSO region, the summer SSTAs in the North Pacific, Indian Ocean, and Atlantic Ocean show different characteristics, which in turn cause circulation anomalies in the tropics and mid-high latitudes through the synergistic effect of SSTAs in different regions. When the key spring ENSO region exhibits warm SSTAs, there is an obvious anticyclonic circulation in the subtropical northwestern Pacific. After the interdecadal shift, this anticyclonic circulation is relatively stronger, but it still fails to transport water vapor to the Beijing-Tianjin-Hebei region. The Beijing-Tianjin-Hebei region is controlled by a cyclonic circulation. In the earlier period, this cyclonic circulation is related to SSTAs in the North Pacific, while in the later period, it is caused by the zonal wave train over the Eurasian continent excited by SSTAs in the North Atlantic. The control of anomalous northerly winds over the Beijing-Tianjin-Hebei region leads to less precipitation.