Mesoscale-dependent near-inertial internal waves and microscale turbulence in the Tsushima Warm Current
Mesoscale-dependent near-inertial internal waves and microscale turbulence in the Tsushima Warm Current
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DOI：
10.1007/s10872-020-00583-1
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发表时间：
2021-01-06
影响因子：
2.3
通讯作者：
Igeta, Yosuke
中科院分区：
文献类型：
--
作者：
Kawaguchi, Yusuke;Wagawa, Taku;Igeta, Yosuke
本文研究了近惯性内波（NIWs）与对马暖流附近背景中尺度场的关系。定期访问佐渡岛近海观测站，评估海水精细尺度和微观尺度的时空变化特征。此外，还从相对涡度和地表地转运动总应变的角度对NIWs进行了检测。在2019年夏季考察期间，在反气旋涡边缘进行的海流和水文调查提供了向下移动的NIWs的明确证据，NIWs在下斜深附近被放大得最多。湍流动能耗散速率和微尺度温度变化的增加与NIW的增大相一致。2019年秋季的考察发现了与成对涡旋中尺度结构相关的波浪和湍流特性的细节，其中气旋和反气旋分别靠近东部和西部。在偶极子核间等轴处发现了niw相关垂直剪切和TKE耗散的放大信号。从内波理论的角度来看，地转流垂直切变引起的斜压项可以解释为NIW通过偶极子岩心之间的下斜脊向下传播。气旋经过日本海中部，由于东风与本州岛山地地形的相互作用，可将动能转化为10公里尺度的内波。
This study examined characteristics of near-inertial internal waves (NIWs) associated with the background mesoscale field near the Tsushima Warm Current. Observational stations off Sado Island were visited recurrently to assess spatiotemporal changes of fine-scale and microscale properties of seawater. Also, NIWs were inspected in terms of relative vorticity and total strain in surface geostrophic motion. During summer expeditions in 2019, current and hydrographic surveys at the rim of an anticyclonic eddy provided clear evidence of downward-travelling NIWs, which were most amplified near the depth of lower pycnocline. The amplification of NIW coincided with elevation in the dissipation rates of turbulent kinetic energy (TKE) and microscale variation of temperature. The fall 2019 expedition found details of wave and turbulence properties associated with the mesoscale structure of paired vortices, where a cyclone and anticyclone were, respectively, adjacent to the east and west. Amplified signals of NIW-related vertical shear and TKE dissipation were found at isopycnals between the dipole cores. From the theoretical perspective of internal wave, the baroclinic term attributable to vertical shear of geostrophic current was interpreted as inducing downward travel of NIW through the lower pycnoclines between the dipole cores. It is also noted that cyclones, passing through the central part of Sea of Japan, can deliver kinetic energy into 10-km scale internal waves as a consequence of interaction between easterly wind and mountainous topography in the Honshu Island.