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黑潮延伸体区域中尺度风应力扰动对海洋的反馈
魏艳州
学位类型博士
导师张荣华
2017-05-08
学位授予单位中国科学院大学
学位授予地点北京
学位专业物理海洋学
关键词黑潮延伸体 中尺度风应力扰动 高分辨率海洋模式 海洋响应
摘要高分辨率的卫星观测风场和海表温度数据表明:中尺度(100~1000千米)风应力和海表温度扰动存在明显的耦合现象。具体而言,风应力幅度、散度/旋度的扰动分别和海表温度、顺风向/切风向海表温度梯度的扰动紧密相关。通过数据分析,我们建立了中尺度风应力扰动和海表温度扰动之间的经验关系,并把这一关系应用于高分辨率的北太平洋海洋环流模式,以此研究了中尺度风应力扰动对海洋的反馈。本文具体分析了中尺度风应力和海表温度的耦合扰动特征,并设计数值实验研究了中尺度风应力扰动对海洋的反馈。
本文首先从卫星观测资料中提取了中尺度风应力和海表温度扰动信号,然后使用回归分析和奇异值分解(SVD)方法研究了它们之间的经验关系以及耦合变化模态。分析结果表明,风应力幅度、散度/旋度的扰动分别和海表温度、顺风向/切风向海表温度梯度的扰动之间具有明显的正相关关系;中尺度风应力和海表温度扰动强度呈现一致的季节变化,即在冬季最大而在夏季最小;中尺度风应力和海表温度扰动之间的耦合系数也具有明显的季节变化,表现为冬季最强而夏季最弱。中尺度风应力和海表温度扰动的前三个SVD模态表明,风应力扰动和海表温度扰动的空间结构一致而时间扩展系数高度相关,时间扩展系数具有季节变化和年际变化。
根据中尺度风应力幅度和海表温度扰动之间的经验关系,以及风应力散度/旋度的扰动和顺风向/切风向海表温度梯度之间的经验关系,本文使用两种方法从海表温度数据中获取中尺度风应力矢量扰动。这两个方法可以分别保持中尺度风应力和海表温度扰动之间的耦合关系,以及中尺度风应力散度/旋度的扰动和顺风向/切风向海表温度梯度之间的耦合关系,并且可以方便地应用于海洋模式。
使用高分辨率海洋模式研究了中尺度风应力扰动对海洋的反馈。这一海洋模式可以较好地模拟中尺度海表温度扰动及其季节变化。通过在海洋模式中加入中尺度风应力反馈并和对照实验进行比较,发现中尺度风应力扰动会对海表温度扰动有抑制作用。进一步的敏感性实验分析表明,中尺度风应力扰动主要通过影响海表面热通量抑制海表温度扰动。中尺度风应力扰动也影响海洋平均态和海表温度的季节变化,并且这一效应在中尺度风应力扰动最为活跃的秋冬季节最为明显。敏感性实验分析表明,中尺度风应力扰动可以通过影响海表热通量和海表动量通量任一方式影响平均海表温度。中尺度风应力扰动也会引起沿黑潮路径的海表面动能的变化,但对黑潮路径的平均位置几乎没有影响。
本文的研究结果对于认识黑潮延伸体区域中尺度海气相互作用以及在气候系统中的作用有一定的参考价值。
其他摘要Mesoscale perturbations (with a size of 100-1000 km) of wind stress magnitude, divergence and curl in the Kuroshio Extension (KE) region are observed to tightly link to those of sea surface temperature (SST), downwind and crosswind SST gradients, respectively. Based on long term satellite observation, empirical relationships between mesoscale wind stress responses and SST forcing are established. These relationships are further used to represent mesoscale wind stress-SST coupling in an ocean model which is based on the Regional Oceanic Modelling Systems (ROMS). This study examines the covariability characteristics of mesoscale wind stress and SST perturbations in the KE, and illustrates the effect of the wind stress perturbations on the ocean.
The mesoscale wind stress and SST perturbations are firstly isolated by using a locally weighted regression method, and then analyzed using the linear regression and Singular Value Decomposition (SVD) methods. It is observed that mesoscale wind stress magnitude, divergence and curl perturbations are positively correlated to SST, downwind and crosswind SST gradients perturbations. The strength of mesoscale wind stress and SST perturbations displays a consistent seasonal variability, with the maximum appeared in winter while the minimum appeared in summer. Coupling coefficient between mesoscale wind stress and SST perturbations also displays distinct seasonal variability, with large value appeared in winter while small value appeared in summer. The leading three SVD modes for mesoscale wind stress and SST perturbations show highly consistent variability in both spatial eigenvectors and temporal expansion coefficients. These temporal expansion coefficients show seasonal and interannual variability.
Based on the observed coupling relationship between mesoscale perturbed wind stress magnitude and SST, and those between wind stress divergence/curl and downwind/crosswind SST gradients, two methods are devised to get the mesoscale wind stress field perturbations from the SST data. The two methods provide convenient ways in which the coupling relationship between mesoscale perturbed wind stress and SST can be hold adequately, and are feasible in eddy-resolving ocean models.
The effect of mesoscale wind stress-SST coupling in the KE is studied by using a high resolution ocean model. This ocean model can simulate the seasonal variability of mesoscale SST perturbations. The mesoscale wind stress field is diagnostically determined from modelled SST by using the empirical relationship between them. Through comparing two experiments with and without the mesoscale wind stress-SST coupling, it is found that the mesoscale perturbed wind stress has a negative feedback on SST perturbations. Analyses of sensitivity experiments suggest that the mesoscale wind stress perturbations inhibit SST perturbations mainly by means of surface heat flux. The mesoscale wind stress perturbations also influence the ocean mean state and seasonal variability of SST in the KE, with large effect in autumn and winter when the mesoscale perturbations are most active. Analyses of sensitivity experiments demonstrate that the mesoscale wind stress perturbations can affect long term mean SST through either the way of surface heat flux or momentum flux. The mesoscale wind stress perturbations also modulate the kinetic energy along the Kuroshio pathway, with little effect on the position of the Kuroshio extension jet.
The results derived in this study help to understand the mesoscale air-sea interaction in the Kuroshio Extension. 
学科领域物理海洋学
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/136561
专题海洋环流与波动重点实验室
作者单位中国科学院海洋研究所
推荐引用方式
GB/T 7714
魏艳州. 黑潮延伸体区域中尺度风应力扰动对海洋的反馈[D]. 北京. 中国科学院大学,2017.
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