科研之友
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摘要
The winter sea surface temperature (SST) anomalies in the Kuroshio and adjacent regions (KAR), which greatly influence the East Asian-North Pacific-North American climate, are closely related to El Nino-Southern Oscillation (ENSO). This SST relationship between the KAR and the equatorial eastern-central Pacific is widely assumed to be symmetric between El Nino and La Nina. Compared to previous studies indicating the significant and strong KAR warming during El Nino winters, this study indicates weakly negative KAR SST anomalies in the composite analysis for all La Nina events. Positive winter KAR SST anomalies unexpectedly appear in approximately half of La Nina events, which counteract negative SST anomalies in the rest of La Nina events. Further analysis suggests that the impact of La Nina on KAR SST anomalies is modulated by the East Asian winter monsoon (EAWM) during early winter. The weaker-than normal EAWM offsets the anomalous northeasterly winds in the KAR induced by La Nina and then reinforces the KAR warming through warm oceanic advection. As for strong EAWM, it enhances the northeasterly winds to the west of an anomalous Philippine Sea cyclone associated with La Nina, leading to KAR cooling with more latent heat flux loss from the ocean and anomalous cold oceanic advection. Additionally, when the EAWM is independent of ENSO and is associated with the western Pacific pattern, it also can exhibit a pronounced influence on the KAR SST anomalies via the major processes of surface latent flux and horizontal heat advection in the ocean, accompanied by a change in Kuroshio transport.
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单位国家气候中心; 中国科学院; 中国科学院大气物理研究所; 热带海洋环境国家重点实验室
