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首页> 外文期刊>Journal of Physical Oceanography >Lagrangian Spectra and Diapycnal Mixing in Stratified Flow
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Lagrangian Spectra and Diapycnal Mixing in Stratified Flow

机译：分层流中的拉格朗日光谱和对流混合

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摘要

Taylor's single-particle dispersion model is revisited and applied to unstratified and density stratified flows using observationally based and theoretical models of the Lagrangian velocity and density spectra, which are compared with existing parameterizations of diapycnal diffusion in these flows. For unstratified homogeneous turbulence, the vertical particle dispersion coefficient K_z computed from model Lagrangian velocity spectra agrees well with contemporary estimates of the diffusivity. For internal waves with no mixing, a large apparent dispersion occurs for times somewhat larger than the inverse buoyancy frequency 1/N. No dispersion occurs at long times. For stratified homogeneous turbulence with energy dissipation rate ε, K_z = dεN~(-2), the same form as Osborn, but with Γ_d of about 2.5. This high value is attributed to apparent dispersion due to internal waves and an improper form of the model spectra that allows internal waves to exist at low frequencies. A diapycnal dispersion coefficient K_* is formulated based on a white spectrum of Lagrangian density change Dρ/Dt with level β_ρχ, where χ is the rate of dissipation of density variance.
机译：使用基于拉格朗日速度和密度谱的观测模型和理论模型，将泰勒的单颗粒弥散模型重新应用于非分层和密度分层流，并将其与这些流中对流扩散的现有参数化进行比较。对于未分层的均匀湍流，从模型拉格朗日速度谱计算出的垂直粒子弥散系数K_z与当代对扩散率的估计非常吻合。对于没有混合的内波，较大的表观色散发生的时间略大于反浮力频率1 / N。长时间不发生分散。对于具有能量耗散率ε的分层均质湍流，K_z =εdεN〜（-2），与Osborn的形式相同，但Γ_d约为2.5。较高的值归因于由于内部波造成的表观色散以及模型频谱的不正确形式，从而导致内部波以低频存在。根据拉格朗日密度变化Dρ/ Dt的白色光谱（级别为β_ρχ）来计算对角线弥散系数K_ *，其中χ是密度方差的耗散率。

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