黑潮延伸体区纬向扰动海温的结构特征及其对系统变异的指示作用分析

为准确描述黑潮延伸体的强度，突出其表面热量输送作用引起的海温调整，提出了纬向扰动海温的概念，基于对NOAA（National Oceanic and Atmospheric Administration）高分辨率海温资料和GODAS（Global Ocean Data Assimilation System）海洋再分析资料的分析表明，气候态的纬向扰动海温与洋流的表面热量输送分布高度一致；对纬向扰动海温年际演变的分析表明，相较于传统的海温异常，纬向扰动海温能够更好地体现出延伸体系统强度的年际振荡，标识出延伸体和亲潮的影响范围；对西北太平洋纬向扰动海温异常的经验模态分解结果的分析表明，前两模态主要反映不受亲潮交汇影响的延伸体收缩和扩张模态，而第三、四模态则反映北侧亲潮的强弱对延伸体扰动海温的影响。涡动动能作为标识延伸体区域的重要动力学指标，在延伸体系统的演变中，与纬向扰动海温通过海洋温度锋的强度和流轴的稳定性紧密联系:纬向扰动海温增大，表明洋流的热量输送作用增强，延伸体强度增强，海温梯度增大，此时海洋温度锋增强，流轴稳定，中尺度涡活动减弱，反之亦然。考虑到纬向扰动海温对延伸体表面热量输送作用具有较好的刻画能力，定义了延伸体热力指数T_p，对比分析表明该指数能较好地标识出延伸体的收缩和扩张状态，对延伸体的纬向伸展距离和流轴的南北振荡同样具有良好的指示作用。

Characteristics of the Zonal Sea Surface Temperature Perturbation and Its Role in Representing the Evolution of the Kuroshio Extension

Zonal sea surface temperature (SST) perturbation (hereafter ZSSTP) is proposed in order to correctly describe the strength of the Kuroshio Extension (KE) and highlight its heat transport effect on SST adjustment. Analysis of the NOAA (National Oceanic and Atmospheric Administration) high resolution SST data and GODAS (Global Ocean Data Assimilation System) re-analysis data indicates that the climatological ZSSTP agrees well the distribution of surface heat transport by currents. Analysis of interannual evolution of ZSSTP indicates that it can represent the interannual oscillation of the KE strength and better identify the ranges influenced by the KE and Oyashio compared to traditional SST anomalies. Empirical orthogonal function (EOF) analysis of ZSSTP in the western North Pacific indicates that the first two EOF modes reflect the contraction and elongation states of the KE system, while the third and fourth EOF modes reflect the impacts by the weakened and enhanced Oyashio, respectively. As an important dynamic parameter to identify the KE region, the eddy kinetic energy (EKE) is closely linked with ZSSTP through the strength of SST front and the stability of currents during the process of the KE evolution. Warm ZSSTP indicates strong surface heat transport, and the SST gradient increases and SST front enhances correspondingly, while currents become more stable and mesoscale eddy activities decrease, and vice versa. Finally, a thermal index T_p is introduced to describe the variation of the thermal state of the KE. It is demonstrated that this index can successfully describe the variation of the zonal stretch and meridional migration of the main axis as well as the evolution of the intensity of the KE.