Alejandra Sanchez-Rios, R. K. Shearman, Craig M. Lee, H. Simmons, Louis St. Laurent, Andrew J. Lucas, T. Ijichi, Sen Jan
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引用次数: 0
摘要
黑潮偶尔会将温暖而含盐的北太平洋海水带入较新鲜的南海海水中,在吕宋海峡以西形成具有复杂温度-盐度(T-S)结构的锋面。在本研究中,我们考察了 2014 年冬季季风季节形成的锋面中北太平洋水层与南海水层交替形成的 T-S 交错结构。利用滑翔机阵列跟随自由浮动的波动力垂直剖面浮筒进行观测,计算细尺度参数特纳角(Tu)和理查森数(Ri),我们确定了在 T-S 交错中观测到的有利于双重扩散对流和剪切不稳定性的区域。我们利用微结构数据评估了双重扩散对流和剪切不稳定性对热变异扩散率 X 的贡献,并将其与之前基于细尺度特性的参数化方案进行了比较。我们发现,当 Tu 和 Ri 都在临界范围内(Tu > 60,Ri < 1/4)时,湍流混合的参数化并不准确。特别是,与盐指过程相关的 X 值(6.7×10-7 K2 s-1)比在只有速度剪切可能驱动混合的区域(8.7×10-8 K2 s-1)高出一个数量级。
Characterization of mixing at the edge of a Kuroshio intrusion into the South China Sea: analysis of thermal variance diffusivity measurements
The Kuroshio occasionally carries warm and salty North Pacific Water into fresher waters of the South China Sea, forming a front with a complex temperature-salinity (T-S) structure to the west of the Luzon Strait. In this study, we examine the T-S interleavings formed by alternating layers of North Pacific water with South China Sea water in a front formed during the winter monsoon season of 2014. Using observations from a glider array following a free-floating wave-powered vertical profiling float to calculate the fine-scale parameters Turner angle, Tu, and Richardson number, Ri, we identified areas favorable to double diffusion convection and shear instability observed in a T-S interleaving. We evaluated the contribution of double diffusion convection and shear instabilities to the thermal variance diffusivity, X, using microstructure data and compared it with previous parameterization schemes based on fine-scale properties. We discover that turbulent mixing is not accurately parameterized when both Tu and Ri are within critical ranges (Tu > 60, Ri < 1/4). In particular, X associated with salt finger processes was an order of magnitude higher (6.7×10−7 K2 s−1) than in regions where only velocity shear was likely to drive mixing (8.7×10−8 K2 s−1).
期刊介绍:
The Journal of Physical Oceanography (JPO) (ISSN: 0022-3670; eISSN: 1520-0485) publishes research related to the physics of the ocean and to processes operating at its boundaries. Observational, theoretical, and modeling studies are all welcome, especially those that focus on elucidating specific physical processes. Papers that investigate interactions with other components of the Earth system (e.g., ocean–atmosphere, physical–biological, and physical–chemical interactions) as well as studies of other fluid systems (e.g., lakes and laboratory tanks) are also invited, as long as their focus is on understanding the ocean or its role in the Earth system.