北太平洋海温对ENSO事件响应的持续性

The persistence of the North Pacific SST response to ENSO events

中文关键词:  北太平洋海温，年代际变化，遥相关，热带降水

英文关键词:North Pacific SST, Interdecadal variation, Teleconnection, Tropical precipitation

中文摘要:

      北太平洋海温的异常变化对海洋生态系统以及全球天气和气候都有着重要影响。北太平洋海温主要受ENSO的影响，并可以从ENSO盛期冬季一直延续到ENSO衰减年春季，存在着明显的持续性。然而，2000年前ENSO的影响仅能维持至次年2月，2000年后却能持续至5月，其持续性呈现明显的年代际增强。基于再分析数据探讨了这一年代际变化的特征以及可能物理机制。结果表明，ENSO事件对冬春季北太平洋海温影响的持续性在2000年后的增强，主要受到北太平洋区域的经向平流反馈以及海表热通量反馈的控制。2000年前，由ENSO激发的遥相关波列在春季已经减弱，热通量反馈的作用使得海温转暖。而在2000年之后，冬季偏西的海温异常使赤道对流可以在次年春季长时间维持在日界线附近，持续激发大气遥相关波列导致北太平洋上空在春季仍然存在显著的气旋性环流异常，并通过经向平流反馈以及热通量反馈使局地海温维持偏冷状态，对ENSO产生持续性响应，增强ENSO事件对其影响的持续性。

英文摘要:

      The anomalies of the sea surface temperature(SST) over the North Pacific have significant impacts on marine ecosystems and global weather and climate. The North Pacific SST is primarily influenced by ENSO and shows a clear persistence. However, its duration manifests as an interdecadal enhancement. Before 2000, the impacts of ENSO only lasted until February of the following year. Whereas after 2000, it could extend until May. Based on the reanalysis data, this study explores the characteristics of this interdecadal change and its potential physical mechanisms. The results indicate that the enhanced persistence of ENSO"s impact on the winter-spring North Pacific SST is mainly controlled by the meridional advection feedback and the sea surface heat flux feedback over the North Pacific. Before 2000, the teleconnection triggered by ENSO had already weakened in spring, leading to warming SST due to the heat flux feedback. However, after 2000, the anomalous westerly SST during winter allowed equatorial convection to persist near the Dateline into the following spring. Thus, the persistent convection continuously excited remote atmospheric teleconnection and resulted in significant cyclonic circulation anomalies over the North Pacific. These anomalous circulations finally leaded to cold SST through meridional advection feedback and heat flux feedback, thereby enhancing the persistence of the North Pacific SST response to ENSO events.