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首页> 外文期刊>Boundary-Layer Meteorology >Analysis of Vertical Turbulent Heat Flux Limit in Stable Conditions with a Local Equilibrium, Turbulence Closure Model
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Analysis of Vertical Turbulent Heat Flux Limit in Stable Conditions with a Local Equilibrium, Turbulence Closure Model

机译：用局部平衡，湍流闭合模型分析稳定条件下的垂直湍流通量极限

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摘要

Assuming that the vertical turbulent heat flux vanishes at extremely stable conditions, one should expect its maximal absolute value to occur somewhere at moderate stability, between a neutral and extremely stable equilibrium. Consequently, in some situations duality of solutions may be encountered (e.g. two different values of temperature difference associated with the same values of heat flux and wind speed). A quantitative analysis of this feature with a local equilibrium Reynolds-stress model is presented. The fixed-wind / fixed-shear maximum has been identified both in the bulk and in single-point flux–gradient relationships (that is, in the vertical temperature gradient and wind-shear parameter domain). The value of the Richardson number corresponding to this maximum is derived from the model equations. To study the possible feedback in strongly stable conditions, weak and intense cooling scenarios have been simulated with a one-dimensional numerical, high-resolution atmospheric boundary-layer model. Despite the rapid cooling, flow decoupling at the surface has not been observed; instead, a stability-limited heat flux is maintained, with a gradual increase of the Richardson number towards the top of the turbulent layer, with some signs of oscillatory behaviour at intermediate heights. Vertical changes of wind shear and the Brunt–Väisälä frequency display a remarkably non-monotonic character, with some signs of a gradually developing instability.
机译：假设垂直湍流的热通量在极其稳定的条件下消失，则应该期望其最大绝对值出现在中性和极其稳定的平衡之间处于中等稳定性的某个位置。因此，在某些情况下，可能会遇到解的对偶性（例如，与热通量和风速的相同值相关联的两个不同的温度差值）。提出了使用局部平衡雷诺应力模型对该特征进行的定量分析。在体积和单点通量-梯度关系中（即在垂直温度梯度和风切变参数域中）都已确定了固定风/固定切变最大值。理查森数的值对应于该最大值，是从模型方程式得出的。为了研究在强稳定条件下的可能反馈，已使用一维数值高分辨率高分辨率大气边界层模型模拟了弱和强冷却情景。尽管进行了快速冷却，但仍未观察到表面处的流体解耦。取而代之的是，维持了有限的热通量，朝着湍流层的顶部逐渐增加了理查森数，并在中间高度出现了一些振荡行为的迹象。风切变和Brunt–Väisälä频率的垂直变化表现出明显的非单调性，并具有逐渐发展的不稳定性的迹象。

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