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Time Scales of Submesoscale Flow Inferred from a Mooring Array

机译:从系泊阵列推断的子尺度流的时间尺度

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摘要

While the distribution of kinetic energy across spatial scales in the submesoscale range (1-100 km) has been estimated from observations, the associated time scales are largely unconstrained. These time scales can provide important insight into the dynamics of submesoscale turbulence because they help quantify to what degree the flow is subinertial and thus constrained by Earth's rotation. Here a mooring array is used to estimate these time scales in the northeast Atlantic. Frequency-resolved structure functions indicate that energetic wintertime submesoscale turbulence at spatial scales around 10 km evolves on time scales of about 1 day. While these time scales are comparable to the inertial period, the observed flow also displays characteristics of subinertial flow that is geostrophically balanced to leading order. An approximate Helmholtz decomposition shows the order 10-km flow to be dominated by its rotational component, and the root-mean-square Rossby number at these scales is estimated to be 0.3. This rotational dominance and Rossby numbers below one persist down to 2.6 km, the smallest spatial scale accessible by the mooring array, despite substantially superinertial Eulerian evolution. This indicates that the Lagrangian evolution of submesoscale turbulence is slower than the Eulerian time scale estimated from the moorings. The observations therefore suggest that, on average, submesoscale turbulence largely follows subinertial dynamics in the 1-100-km range, even if Doppler shifting produces superinertial Eulerian evolution. Ageostrophic motions become increasingly important for the evolution of submesoscale turbulence as the scale is reduced-the root-mean-square Rossby number reaches 0.5 at a spatial scale of 2.6 km.
机译:虽然已经从观察结果估计了基质尺度范围(1-100公里)的空间尺度跨空间尺度的分布,但相关的时间尺度在很大程度上不受约束。这些时间尺度可以对基础尺度湍流的动态提供重要的洞察,因为它们有助于量化流动是下降的程度,因此受到地球旋转的限制。这里,系泊阵列用于估计东北大西洋的这些时间尺度。频率分辨的结构功能表明,在约10公里的空间尺度下的精力冬季血液浊度湍流在约1天的时间尺度上发展。虽然这些时间尺度与惯性周期相当,但观察到的流程还显示出在光秃秃的流程到前导顺序的子分泌流的特性。近似亥姆霍兹分解显示了以其旋转分量支配的10-km流量,并且这些刻度下的根均线罗斯比数估计为0.3。这种旋转的优势和罗斯比数量低于一个持续到2.6公里,尽管大幅上乘欧拉的演变,所以停泊阵列可通过的最小空间秤。这表明提子张浊的拉格朗日演化比从停泊估计的欧拉时间尺度慢。因此,观察结果表明,平均而言,即使多普勒换档产生高度欧拉进化,平均而言,血管湍流的平均性湍流很大程度上遵循1-100公里范围内的子系统动力学。由于尺度减少,因此逐渐减少的血液扫带湍流的演变变得越来越重要 - 以2.6公里的空间等级达到0.5的根平均方形罗斯比数。

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  • 来源
    《Journal of Physical Oceanography》 |2020年第4期|1065-1086|共22页
  • 作者单位

    California Institute of Technology Pasadena California;

    Tel Aviv University Tel Aviv Israel and University of California Los Angeles Los Angeles California;

    University of Southampton Southampton United Kingdom;

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  • 正文语种 eng
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