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首页> 外文期刊>Journal of Physical Oceanography >Can Lagrangian Tracking Simulate Tracer Spreading in a High-Resolution Ocean General Circulation Model?
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Can Lagrangian Tracking Simulate Tracer Spreading in a High-Resolution Ocean General Circulation Model?

机译：拉格朗日跟踪是否可以在高分辨率海洋一般环流模型中模拟示踪剂的扩散？

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To model tracer spreading in the ocean, Lagrangian simulations in an offline framework are a practical and efficient alternative to solving the advective-diffusive tracer equations online. Differences in both approaches raise the question of whether both methods are comparable. Lagrangian simulations usually use model output averaged in time, and trajectories are not subject to parameterized subgrid diffusion, which is included in the advection-diffusion equations of ocean models. Previous studies focused on diffusivity estimates in idealized models but could show that both methods yield similar results as long as the deformations-scale dynamics are resolved and a sufficient amount of Lagrangian particles is used. This study compares spreading of an Eulerian tracer simulated online and a cloud of Lagrangian particles simulated offline with velocities from the same ocean model. We use a global, eddy-resolving ocean model featuring 1/20 degrees horizontal resolution in the Agulhas region around South Africa. Tracer and particles were released at one time step in the Cape Basin and below the mixed layer and integrated for 3 years. Large-scale diagnostics, like mean pathways of floats and tracer, are almost identical and 1D horizontal distributions show no significant differences. Differences in vertical distributions, seen in a reduced vertical spreading and downward displacement of particles, are due to the combined effect of unresolved subdaily variability of the vertical velocities and the spatial variation of vertical diffusivity. This, in turn, has a small impact on the horizontal spreading behavior. The estimates of eddy diffusivity from particles and tracer yield comparable results of about 4000 m(2) s(-1) in the Cape Basin.
机译：为了对示踪剂在海洋中的扩散进行建模，在离线框架中进行拉格朗日模拟是在线求解平流-扩散示踪剂方程的一种实用且有效的替代方法。两种方法的差异提出了两种方法是否可比的问题。拉格朗日模拟通常使用时间平均的模型输出，并且轨迹不受参数化子网格扩散的影响，这包括在海洋模型的对流扩散方程中。先前的研究集中在理想化模型中的扩散率估计上，但是可以证明，只要解决了变形尺度的动力学问题并且使用了足够数量的拉格朗日粒子，这两种方法都能得出相似的结果。这项研究比较了在线模拟的欧拉示踪剂和离线模拟的拉格朗日粒子云的传播速度，这些云来自同一海洋模型。我们在南非周围的Agulhas地区使用全球分辨率为1/20度的涡旋分辨海洋模型。示踪剂和颗粒在Cape Basin的一次一步中在混合层以下释放，并整合了3年。大型诊断（如浮标和示踪剂的平均路径）几乎相同，并且一维水平分布没有显着差异。垂直分布的差异（由于减小的垂直扩散和向下位移而导致）是由于垂直速度的未解决的次日变化和垂直扩散率的空间变化共同作用的结果。反过来，这对水平扩展行为的影响很小。来自颗粒和示踪剂的涡流扩散率估计在开普盆地产生约4000 m（2）s（-1）的可比结果。

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