Impact of Warming Trend in Western Equatorial Pacific on Modulating the Triple‐Dip La Niña and Its Associated Teleconnection in 2020–2022

In this study, we investigated the triple‐dip La Niña during 2020–2022 by comparing it with the previous (1973–1975 and 1998–2000) La Niña events. We found that the cold sea surface temperature (SST) in the eastern equatorial Pacific was moderate during the study period; however, the accompanying near‐surface easterly wind anomaly was unusually stronger during its lifecycle than during the previous two events. The maintenance of 2020–2022 La Niña appeared to be attributable to the strong zonal SST gradient. The strong zonal SST gradient resulted from the La‐Niña‐associated interannual SST anomaly, which was further enhanced by a warming trend in the western equatorial Pacific (165°E−160°W, 5°S–5°N) and the interdecadal oscillation of the Pacific‐Decadal‐Oscillation‐associated cold SST in the eastern tropical Pacific. The warming trend in the western equatorial Pacific, with a faster warming speed than global warming, also modified the La‐Niña‐associated Pacific–North American teleconnection to shifted eastward. Plain Language Summary The La Niña during 2020–2022 was the first triple‐dip event in the 21st century. It induced several major disasters worldwide, such as the record flooding in Pakistan caused 30 million people to lose their homes and took the lives of more than 1,000 individuals. However, how this long‐duration La Niña was maintained remained unclear. The physical processes related to the 2020–2022 La Niña were investigated by comparing them with those of the previous 3‐year La Niña events (1973–1975 and 1998–2000). The major distinctive feature of the 2020–2022 La Niña was the moderate negative sea surface temperature (SST) anomaly in the eastern equatorial Pacific, which was accompanied by an unusually strong near‐surface easterly wind anomaly in the central equatorial Pacific. Our study revealed the maintenance of the triple‐dip La Niña during 2020–2022 was attributable to the strong zonal SST gradient between the western and eastern equatorial Pacific, with the western waters being dominated by a warming trend and the eastern waters being influenced by the cold phase of the Pacific Decadal Oscillation. The warming trend in the western equatorial Pacific provided a favorable background for a triple‐dip La Niña event and also modified the La‐Niña‐associated Pacific–North American teleconnection so that it shifted eastward. Key Points The La‐Niña‐associated cold SST was moderate during 2020–2022, but the accompanying easterly wind anomaly reac