【作者】 李春；

【导师】 吴立新；

【作者基本信息】 中国海洋大学 ， 物理海洋， 2010， 博士

【摘要】 北太平洋海洋环流调整及其对太平洋气候年代际变化的影响一直是海洋与气候研究领域的前沿科学问题,其中的一个关键问题就是北太平洋海洋环流如何调整,产生海表温度异常并进一步对大气环流产生反馈作用。本文围绕着这一前沿关键科学问题,采用全球海洋-大气耦合模式FOAM1.5并借助耦合模式的“部分耦合”技术,结合观测资料分析提取出的大气强迫模态,系统研究了以下两个问题：(1)北太平洋风生环流在PNA型／NPO型异常风应力强迫下的动力调整及其对大气环流的反馈作用(2)异常风应力强迫下北太平洋副热带与热带的相互作用得到了如下创新性的结论：(1)PNA型正位相异常风应力强迫下,北太平洋副极地环流异常加强且向南扩张,使北太平洋副热带环流与副极地环流的边界(KOE纬向流轴)向南偏移；北太平洋SST的响应类似于PDO模态正位相异常。海洋环流的调整对北太平洋大气环流异常反馈体现为明显的季节性特征：冬季主要表现为准正压的低压槽异常且以正位相NPO型大气环流异常为主；而夏季主要表现为对流层低层高压脊异常与对流层高层低压槽异常的斜压响应。(2)NPO型正位相异常风应力强迫下,整个北太平洋环流系统加强,造成KOE纬向流轴加强；北太平洋SST的响应类似于NPGO模态正位相异常。海洋环流调整在冬季对北太平洋大气环流产生类似PNA型负位相环流异常的反馈。(3)局地海气耦合在北太平洋海洋环流调整中也起着重要的作用：使北太平洋环流系统向北偏移,从而使KOE纬向流轴在PNA型正位相异常风应力强迫下,向南偏移减少30%左右；在NPO型正位相异常风应力强迫下向北偏移约0.5个纬度。(4)PNA型异常风应力强迫下,北太平洋影响热带太平洋的物理过程有四种：表面耦合的WES正反馈机制；STC加强机制；Subduction过程和北太平洋西边界的沿岸Kelvin波传播机制。热带太平洋通过局地海气耦合在冬季对北太平洋产生负位相PNA型的大气环流异常反馈,进而抵消部分大气强迫场。(5)PNA型风应力强迫下,通过海洋与大气的非线性相互作用,使下游北大西洋产生类似“三极子”结构的SST异常和上空NAO型的大气环流异常。综上所述,关于海洋环流在北太平洋气候年代际变化中的作用,本文有以下三点贡献：(1)发现PNA型风应力强迫通过海-气耦合会激发NPO型的大气环流异常,NPO型风应力强迫会激发PNA型大气环流异常,且存在很强的正负不对称性；(2)揭示PNA型风应力强迫会导致黑潮流轴的南北移动,NPO型风应力会导致黑潮加速或减速,而北太平洋局地的海-气耦合作用会导致黑潮从一种型态趋向另一种型态；(3)揭示了PNA型异常风应力强迫下北太平洋与热带太平洋的相互作用中的四种物理机制,发现冬季热带太平洋响应会减弱热带外强迫,形成负反馈。更多还原

【Abstract】 Adjustment of the North Pacific oceanic circulation and its impact on Pacific decadal climate variation has long been the scientific frontier issues in ocean dynamics and climate research.A key scientific question within is how the oceanic gyres adjust and generate Sea Surface Temperature (SST) anomalies,and further feedbacks to general circulation of atmosphere.A global ocean-atmosphere coupled model,named as FOAM1.5,is used to investigate this scientific issue.Based on atmospheric forcing modes picked up from NCEP/NCAR reanalysis data and using the "Partial Coupling" surgery of coupled GCM models,we systematically explore two issues as follows:(1)Adjustment of the North Pacific wind-driven circulation under the PNA-like and NPO-like anomalous wind stress forcing pattern and its impacts on atmospheric circulation.(2) Interaction of the subtropical North Pacific and the tropical Pacific under anomalous wind stress forcing.The innovative conclusions can be summarized as follow:(1)Under the positive PNA-like anomalous wind stress forcing, subpolar oceanic gyre in the North Pacific is strengthened and stretches southward,which leads to a southward shift of the boundary between subtropical and subpolar gyres, that is,the zonal jet of Kuroshio-Oyashio Extension(KOE).The response of SST presents the positive PDO-like anomalies.The feedbacks of the oceanic adjustment to the atmosphere of the North Pacific display significant seasonal ity.In winter,atmospheric response is dominated by the quasi-barotropic low-trough anomalies,which resembles positive NPO-like anomalous atmospheric circulation.In summer, baroclinic anomalies dominate the atmospheric response with high-ridge anomaly in the low troposphere and low-trough anomaly in the upper troposphere.(2)Under the positive NPO-like anomalous wind stress forcing,the North Pacific oceanic circulation system including the subtropical and the subpolar gyres are consistently strengthened,which induces acceleration of KOE zonal jet.The impact of the North Pacific oceanic adjustment to atmospheric circulation above is to generate the quasi-barotropic high-ridge anomalies,which resembles negative PNA-like anomalous atmospheric circulation in winter.(3)Local air-sea coupling is important for adjustment of oceanic gyres in the North Pacific.It is the role of air-sea coupling that makes oceanic circulation system shifts northward,which leads to KOE zonal jet shifts southward less about 30% driven by the positive PNA-like anomalous wind stress forcing,and shifts about 0.5-latitude northward under positive NPO-like anomalous wind stress forcing.(4) Under the positive PNA-like anomalous wind stress forcing,there are four primary physical mechanisms responsible for transmitting anomalous signal from the North Pacific to tropical Pacific:surface coupled Wind-Evaporation-SST(WES) positive feedback,enhanced STC, subduction process and the effect of coastal Kelvin wave.Feedback of air-sea coupling in the tropical Pacific to North Pacific atmospheric circulation generates negative PNA-like anomalies,which partially offsets the atmospheric forcing. (5)Under the PAN-like anomalous wind stress forcing,the North Pacific coupled adjustments triggers the triple-like structure SST anomalies in the downstream and positive NAO-like atmospheric circulation anomalies in the North Atlantic.In summary,there are three major findings on the roles of oceanic circulation in modulating Pacific decadal climate variation,which can be described as follows:(1) The PNA-like wind stress forcing may induce NPO-like atmospheric circulation anomalies,and the NPO-like wind stress forcing may trigger PNA-like atmospheric circulation anomalies,and there appears strong positive-negative asymmetry within.(2)The PNA-like wind stress forcing causes Kuroshio jet shifts northward or southward,and the NPO-like wind stress forcing leads to acceleration or deceleration of the Kuroshio jet,while local air-sea coupling in the North Pacific can modulate the shift of Kuroshio from one mode to another mode.(3) The North Pacific can influence tropical Pacific through four physical processes and then return the negative feedback from tropical Pacific to the North Pacific,which can weaken the extratropical forcing.更多还原