Dynamics of Cross-Isobath Dense Water Transport Induced by Slope Topography
Dynamics of Cross-Isobath Dense Water Transport Induced by Slope Topography
复制标题
斜坡地形引起的跨等线浓水输送动力学
DOI：
10.1175/jpo-d-10-05014.1
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发表时间：
2011
影响因子：
3.5
通讯作者：
H.Hasumi
中科院分区：
文献类型：
--
作者：
Matsumur Y.;H.Hasumi
基于高分辨率数值试验、简化的水粒子平流分析模式和理想化的敏感性试验，研究了小尺度地形变化引起的稠密水团跨等深线下坡输运动力学。海脊的存在导致了两种不同的浓水跨等深线下坡输送过程：海脊东侧的强而窄的下坡流和海脊西侧的气旋性涡旋。前一种下坡流是响应于山脊附近坡角的快速增大而产生的。后一种涡流是由靠近波峰的稠密水层拉伸而形成的，那里的等深线曲率很大，离岸离心力克服了向海岸的科里奥利力。通过对曲线等深线斜坡上流体质点运动方程的简单分析，导出了异重流是否沿等深线运动的一般判据，并得到了理想灵敏度实验的支持。稠密水的跨等深线输送发生的位置由等深线曲率、行星涡度和坡度角的空间导数之间的相对大小决定。基于这些论点，提出了一个参数化来表示未解决的小尺度地形在粗分辨率模式的影响。
Dynamics of cross-isobath downslope transport of a dense water mass induced by small-scale topographic variation is investigated based on a high-resolution numerical experiment with realistic settings, a simplified analytical model for water particle advection, and idealized sensitivity experiments. The existence of a submarine ridge induces two different processes for cross-isobath downslope transport of dense water: a strong but narrow and thin downslope current at the east side of the ridge and cyclonic eddies with dense water cores to the west of the ridge. The former downslope current is produced in response to the rapid increase of slope angle near the ridge. The latter eddies are formed by stretching of the dense water layer near the crest, where isobath curvature is so high that offshore centrifugal force overcomes the coastward Coriolis force. From a simple analysis on the equation of motion for a fluid particle placed on a slope with curved isobaths, a general criterion that describes whether a density current follows or crosses isobaths is derived, which is supported by idealized sensitivity experiments. The location where cross-isobath transport of dense water takes place is determined by relative magnitude between spatial derivatives of isobath curvature, planetary vorticity, and slope angle. Based on these arguments, a parameterization is proposed to represent the effect of unresolved small-scale topography in coarse-resolution models.