Potential Impact of Winter–Spring North Atlantic Tripole SSTAs on the Following Autumn–Winter El Niño–Southern Oscillation: Bridging Role of the Tibetan Plateau.

Sea surface temperature anomalies (SSTAs) over the North Atlantic could stimulate the El Niño–Southern Oscillation (ENSO) events through regulating the tropical and mid‐latitude atmospheric circulations. Whether the Tibetan Plateau (TP) play an important bridging role in the mid‐latitude pathway has been rarely considered. Observational analysis and model simulations show that the spring TP surface wind speed dipole mode forced by the winter–spring North Atlantic tripole SSTAs can induce surface zonal wind anomalies over the equatorial western Pacific from April to June through the Indo‐Pacific gearing process, favoring the occurrence of subsequent autumn–winter ENSO events through the Bjerknes feedback. Moreover, a flattened TP will obviously weaken the atmospheric and oceanic responses associated with ENSO development to the North Atlantic tripole SSTAs forcing. Quantitatively, the TP's bridging effect accounts for about 38% proportion in the above process. Our finding provides a new insight in understanding the mid‐latitude pathway. Plain Language Summary: El Niño‐Southern Oscillation (ENSO) exerts pronounced climate impacts across the globe, but it is influenced by many factors. Previous studies have revealed that sea surface temperature anomalies (SSTAs) over the North Atlantic could stimulate ENSO events through two pathways, directly through regulating the tropical atmospheric circulation and indirectly via stimulating the mid‐latitude atmospheric teleconnection. In the indirect pathway, the physical mechanisms involve very complex interactions among multiple atmospheric and oceanic systems. Here, we reveal that the Tibetan Plateau (TP) plays an important bridging role in the indirect pathway. Both observations and model simulations show that winter‐spring positive North Atlantic tripole SSTAs can trigger downstream‐propagating Rossby wave train, which further cause an upper‐level anomalous cyclone (anticyclone) over the western TP (subtropical central‐western Pacific) during April and June. Consequently, upper‐level convergences and lower‐level divergences appear over the Maritime Continent, which induce surface westerly anomalies over the equatorial western Pacific, favoring the occurrence of subsequent autumn‐winter El Niño events. After flattening the TP in climate model, the overall responses of atmospheric and oceanic processes associated with El Niño development to the North Atlantic tripole SSTAs will be obviously weakened. Quantitatively, the TP's bridging effect accounts for about 38% contribution in the above process. Key Points: The spring Tibetan Plateau (TP) thermal forcing could act as a medium in linking the preceding North Atlantic tripole Sea surface temperature anomalies (SSTAs) and the subsequent El Niño–Southern Oscillation (ENSO) eventsExcluding the TP's effect will weaken the responses of processes associated with ENSO development to the North Atlantic tripole SSTAs forcingQuantitatively, the TP's bridging effect accounts for about 38% proportion in the above process [ABSTRACT FROM AUTHOR]