题目🛌🏼:A Novel Mechanism for Extreme El Niño Events: Interactions between Tropical Cyclones in the Western North Pacific and Sea Surface Warming in the Eastern Tropical Pacific
报告摘要🧔🏿♀️:
This study presents a novel mechanism for the generation of extreme El Niño events by analyzing interactions between tropical cyclones (TCs) in the western North Pacific (WNP) in spring [March–May (MAM)] and summer [June–August (JJA)] and sea surface warming in the eastern tropical Pacific. It is suggested that anomalously strong TCs in the WNP in MAM and JJA are essential for the formation of extreme El Niño events. MAM TCs excite considerable westerly wind bursts (WWBs) and facilitate the generation of El Niño events in late spring. The sea surface temperature (SST) in the central-eastern tropical Pacific increases prominently during the following summer, which is due to the warm water carried by downwelling Kelvin waves induced by the anomalous westerlies in the western tropical Pacific associated with the WNP TCs, as well as the lessening cold water upwelling resulting from the deepening thermocline in the eastern tropical Pacific. The developing El Niño in turn contributes to the TC activities over the southeastern quadrant of the WNP in summer, characterized by a stronger intensity, higher frequency, and longer duration. The resulting JJA TC-induced westerlies could further enhance the eastern tropical Pacific warm SST anomalies, and thus an extreme El Niño event tends to appear in the following autumn and winter. These physical processes are verified by several sets of atmosphere–ocean coupled model experiments.