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首页> 外文期刊>Journal of the Atmospheric Sciences >On adding thermodynamic damping mechanisms to refine two classical models of katabatic winds
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On adding thermodynamic damping mechanisms to refine two classical models of katabatic winds

机译：在添加热力学阻尼机制以完善两种经典的方差风模型时

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摘要

The Prandtl and layer-averaged models of katabatic winds contain some nonphysical singularities in the analytical solutions, which give unbounded steady flow anomalies at zero slope angles or adiabatic lapse rates. This study presents some simple refinements of these two classical models, in which the aforementioned singularities are removed when Newtonian cooling and Rayleigh friction are included in the system. It is pointed out that, in the limit of zero slope angles or adiabatic lapse rates, the along-slope buoyancy force and the adiabatic heating caused by air descending approach zero. Under such circumstances, a bounded steady solution for the katabatic winds is impossible unless some damping mechanisms are included to retard the anomalies induced by the radiative cooling effect in the boundary layer. Newtonian cooling and Rayleigh friction are the two simplest thermodynamic damping mechanisms that can be included to balance the effects of eddy viscosity and eddy thermal conductivity in the katabatic-flow model. Physically speaking, the Newtonian cooling term represents a small partition of the radiative effect and the Rayleigh friction term represents an approximation of the bottom drag effect in a turbulent boundary layer.
机译：普特朗特风和层均风的平均模型在解析解中包含一些非物理奇异点，这些奇异点在零斜角或绝热流失率下给出了无界的稳定流异常。这项研究提出了这两个经典模型的一些简单改进，其中当系统中包括牛顿冷却和瑞利摩擦时，上述奇异点被消除了。要指出的是，在零倾斜角或绝热消失率的极限下，由空气下降引起的沿斜坡的浮力和绝热加热接近零。在这种情况下，除非包含一些阻尼机制以阻止边界层中辐射冷却效应引起的异常，否则就不可能有针对风的有界稳定解。牛顿冷却和瑞利摩擦是最简单的两个热力学阻尼机制，可以用来在涡流模型中平衡涡流粘度和涡流热导率的影响。从物理上讲，牛顿冷却项代表辐射效应的一小部分，瑞利摩擦项代表湍流边界层中底部阻力效应的近似值。

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