Abstract The Walker Circulation (WC) is a crucial atmospheric circulation system over the tropical Pacific. While current climate models show WC weakening in recent decades, observations exhibit an intensification instead. This discrepancy indicates critical gaps in understanding the interdecadal variability of the tropical atmospheric circulation. The East Asian winter monsoon (EAWM), one of the most active atmospheric circulation systems in the extratropical regions, can significantly influence tropical climates. Using reanalysis data during 1948–2020, this study reveals that the interdecadal weakening of the EAWM may have enhanced the WC since the mid‐1980s. During 1948–1986, the northerly wind anomalies associated with strong EAWM extended southward into the western tropical Pacific (WTP), cooling the local sea surface temperature (SST) and intensifying the low‐level westerlies over the WTP in the winter. In the following summer and winter, the westerly anomalies caused pronounced SST warming in the central and eastern equatorial Pacific, and thus weakened WC appeared in this period. However, during 1987–2020, the interdecadal weakening of EAWM decoupled with the tropical westerly anomalies, thereby displaying negligible impacts on the SST warming. Both the weakened westerly anomalies and SST warming were favorable for the strengthening of the WC in the following summer and winter. Therefore, an intensified WC appeared. Our findings reveal the importance of the extratropical origin from EAWM for the strengthening of the WC in the recent decades.
Han et al. (Tue,) studied this question.