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On the eddy mixing and energetics of turbulence in a stable atmospheric boundary layer |
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| Authors: | A F Kurbatskii L I Kurbatskaya |
| Institution: | 1. Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Institutskaya ul. 4/1, Novosibirsk, 630090, Russia 2. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia 3. Institute of Numerical Mathematics and Mathematical Geophysics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent??eva 6, Novosibirsk, 630090, Russia |
| Abstract: | Some changes in the eddy mixing in the atmospheric boundary layer (ABL) are investigated with the use of the mesoscale RANS turbulence model. It is found that the behavior of parameters of the eddy turbulence mixing is in compliance with the recently obtained data of laboratory and atmospheric measurements. In particular, the flow Richardson number (Ri f ) during the transient flow to a strongly stable state can behave nonmonotonically, growing with the increasing gradient Richardson number (Ri g ) to the state of saturation at a certain gradient Richardson number (Ri g ? 1), which separates two different turbulent regimes: the regimes of strong mixing and weak mixing. An analysis of the energetics based on the balance equations of kinetic and potential turbulence energies shows, in particular, that the weak mixing (Ri g > 1) is quite capable of transferring momentum. This phenomenon can be explained not only by the fact that the flow is sustained by propagating internal waves, which effectively transfer momentum under strong stratification conditions, but also by the fact that turbulence permanently arises in the free atmosphere and in the deep ocean at Ri g ? 1. |
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