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观测事实显示,在E1 Ni(?)o发生期间,伴随着赤道中东太平洋的增暖,中纬度北大平洋中部表层海温（SST）常出现冷距平,而北美大陆西海岸SST则出现暖距平。借助观测资料分析和海气耦合模式模拟两种手段,检验了北太平洋对ENSO事件的上述响应。观测证据和数值模拟都支持有关学者提出的“大气桥”概念,即大气对赤道中东太平洋SST异常增暖的响应,随后强迫中纬度北太平洋,并导致那里SST的变冷,从而起到了连接热带和热带外特别是中纬度北太平洋的“桥梁”的作用。关于其机制,本文认为主要是海洋对大气强迫的动力响应导致那里的SST变冷,尽管潜热通量的贡献也很显著。至少模式结果证明短波辐射、长波辐射和感热通量的贡献都是次要的。进一步的分析揭示,北太平洋存在着线性独立于ENSO事件的所谓“北太平洋模态”,在空间型上,它和线性地依赖于ENSO事件的模态非常相近,即它们的纬向结构都呈现出扁平的“双极”型,只是彼此间SST距平极大值的中心位置不同。模拟结果表明,北太平洋模态与大气的耦合作用,主要是通过海气热通量交换实现的,其中短波辐射和长波辐射的作用居主导地位,而潜热通量的贡献则基本可以忽略。
Observations show that during the E1 Ni (?) O period, the anomalous cold anomalies often occur in the mid-northern North Pacific Ocean with the warming of the equatorial central and eastern Central Pacific, while the SST of the western coast of North America appears warm level. The above responses to the ENSO event in the North Pacific Ocean were tested by means of both observational data analysis and ocean-atmosphere coupling model simulations. Both the observational evidence and the numerical simulation support the concept of “atmospheric bridge” proposed by the scholars, that is, the atmospheric response to the SST anomalous warming in the equatorial central and eastern equatorial Pacific and subsequent forced mid-latitude North Pacific Ocean, leading to cooling of the SST there, And the role of “bridge” in the North Pacific, especially in the mid-latitudes of the tropics. Regarding its mechanism, this paper argues that it is primarily the dynamic response of the ocean to atmospheric forcing that leads to a cooling of the SST there, although the contribution of the latent heat flux is also significant. At least the model results demonstrate that the contributions of shortwave radiation, longwave radiation and sensible heat flux are all secondary. Further analysis revealed that there is a so-called “North Pacific mode” in the North Pacific that is linearly independent of the ENSO event. In the spatial model, it is very similar to the one that depends linearly on ENSO events, ie, their zonal structures are presented The flat “bipolar” type is only different from the center of the SST anomaly in each other. The simulation results show that the coupling between the North Pacific model and the atmosphere is mainly achieved through the exchange of heat and air fluxes, of which shortwave and longwave radiation play a dominant role, while the contribution of latent heat flux is negligible.