Interdecadal Shift of the Relationship between ENSO and Winter Synoptic Temperature Variability over the Asian-Pacific-American Region in the 1980s

In this study, the interdecadal variability of the relationship between ENSO and winter synoptic temperature variability (STV) over the Asian-Pacific-American region is investigated based on observational data from 1951 to 2018. An interdecadal shift in the ENSO-STV relationship occurred in the 1980s over Eastern China, changing from significant in period 1 (P1; 1951-87) to insignificant in period 2 (P2; 1988-2018). But the ENSO-STV relationship is significantly stable over North America for the whole period. In addition, a possible reason for this interdecadal shift in the ENSO-STV relationship over Eastern China is also investigated. During P1, the ENSO pattern is significantly correlated to the temperature gradient over Northeast Asia, which is the key region influencing the intensification of extratropical eddies. The intensification of extratropical eddies over Northeast Asia is directly associated with the magnitude of STV over Eastern China. But in P2, the ENSO pattern is not related to the temperature over Northeast Asia. Therefore, the change in the ENSO pattern from P1 to P2 contributes to the interdecadal shift in the ENSO-STV relationship in the 1980s over Eastern China by influencing the temperature gradient over Northeast Asia, while ENSO can influence the temperature gradient over North America for the whole period. Furthermore, the possible role of the ENSO patterns in P1 and P2 is also examined by using an atmospheric general circulation model, highlighting that the pattern of SST variation is a determining factor in regulating STV in different regions.