黑潮—亲潮延伸体海域“异常”中尺度涡生消机制的研究

In general, a mesoscale cyclonic (anticyclonic) eddy has a colder (warmer) core, due to the eddy-induced upwelling (downwelling) modulated by Coriolis force, accordingly it is also considered as a cold (warm) eddy. However, the applicant found that there are a large number of “abnormal” mesoscale cyclonic (anticyclonic) eddies associated with warm (cold) cores in the North Pacific Ocean, especially in the Kuroshio-Oyashio Extension region (Sun et al., 2019). These “abnormal” eddies pose a challenge to the previous work using single remote sensing data for detection and analysis. Given that, this proposal aims at the “abnormal” mesoscale eddies in the Kuroshio-Oyashio Extension region based on the prior research of the applicant. Firstly, combined with multi-source observations and eddy-resolving model data, large sample statistical analysis is performed to explore the physical processes in the whole life cycle. Secondly, their formation/decaying mechanisms are investigated theoretically by means of instability analysis, energy diagnose and numerical simulation. Through these researches, the results will help clarify the formation/decaying mechanisms of the “abnormal” mesoscale eddies within the Kuroshio-Oyashio Extension region, and further improve the understanding of the oceanic mesoscale dynamics.

海洋中尺度气旋涡（反气旋涡）在科氏力的作用下，会诱导出海水的辐散（辐聚）运动，造成涡旋内部的海水通常比周围同深度层上的海水偏冷（偏暖），故其往往又被称为冷涡（暖涡）。然而申请人在最近的研究中发现，在北太平洋海域还存在着相当数量的气旋涡（反气旋涡）内部偏暖（偏冷）的“异常”涡旋，该现象在黑潮—亲潮延伸体海域尤为显著（Sun et al., 2019）。“异常”中尺度涡现象的发现对以往基于单一遥感数据的涡旋统计工作提出了挑战。鉴于此，本项目将以黑潮—亲潮延伸体海域“异常”中尺度涡为研究对象。首先，结合长时间序列的多源观测及涡分辨数值模式数据，对“异常”中尺度涡的生消过程进行大样本统计分析；其次，从稳定性分析、能量诊断等角度对其生消机制进行理论探究与数值诊断；最终，通过本项目的实施，阐明黑潮—亲潮延伸体海域“异常”中尺度涡的生消机制，进一步完善对海洋中尺度涡旋动力学的认识。

“异常”中尺度涡旋是指海洋中的气旋暖涡和反气旋冷涡。这两类有别于常规中尺度涡旋的现象在黑潮-亲潮延伸体区域尤为常见。针对“异常”涡旋的研究，有助于完善中尺度涡旋动力学的内容，对于区域海洋模式精细化的预报和各种海上军事、经济活动都具有重要的意义。本研究基于卫星观测资料、涡分辨数值模式等资料对黑潮-亲潮延伸体海域的中尺度涡旋现象开展了包括其空间分布、涡旋半径、垂向穿透深度、涡旋移动速度等基本特征；“异常”涡旋诱导的海水温度、盐度、位势密度的变化等涡旋影响以及造成“异常”涡旋的生成机制等多个维度的研究，主要研究成果概括如下：（1）在空间分布上，“异常”涡旋主要分布在近岸流系复杂的海域；在季节尺度上“异常”涡旋在夏秋季多、冬春季节少；在三维结构上，“异常”涡旋多表现为“碗状”，且存在上层为“异常”涡旋，下层为正常涡旋的现象。（2）“异常”涡旋诱导的海水温度的变化程度只有正常涡旋的一半，且存在垂向不同层中温度异常符号反转的情况；“异常”涡旋诱导的盐度异常比正常涡旋诱导的的盐度异常更大，且在垂向上具有一致的变化趋势；“异常”涡旋诱导的位势密度的变化与正常涡旋基本一致。（3）涡旋在衰亡期自身结构的不稳定性、涡旋与涡旋的相互作用、周围特殊水体的影响是“异常”涡旋生成的三种可能的机制。