Changeset 11677
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 20191011T00:15:29+02:00 (12 months ago)
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NEMO/trunk/doc/latex/NEMO/subfiles/chap_ZDF.tex
r11676 r11677 582 582 ML are handled by the Ri # dependent scheme. 583 583 584 \subsubsection{The structure of the OSBL} 585 Figure \ref{OSM1} 586 584 \subsubsection{Depth and velocity scales} 585 The model supposes a boundary layer of thickness $h_{\mathrm{bl}}$ enclosing a wellmixed layer of thickness $h_{\mathrm{ml}}$ and a relatively thin pycnocline at the base of thickness $\Delta h$; Fig.~\ref{fig: OSBL_structure} shows typical (a) buoyancy structure and (b) turbulent buoyancy flux profile for the unstable boundary layer (losing buoyancy at the surface; e.g.\ cooling). 586 \begin{figure}[!t] 587 \begin{center} 588 \includegraphics[width=\textwidth]{Fig_ZDF_OSM_structure_of_OSBL} 589 \caption{ 590 \protect\label{fig: OSBL_structure} 591 The structure of the entraining boundary layer. (a) Mean buoyancy profile. (b) Profile of the buoyancy flux. 592 } 593 \end{center} 594 \end{figure} 595 The pycnocline is shallow but important, since here the turbulent OSBL interacts with the underlying ocean. In a finite difference model the pycnocline must be at least one model level thick. The pycnocline in the OSMOSIS scheme is assumed to have a finite thickness, and may include a number of model levels. This means that the OSMOSIS scheme must parametrize both the thickness of the pycnocline, and the turbulent fluxes within the pycnocline. 596 597 Consideration of the power input by wind acting on the Stokes drift suggests the Langmuir velocity scale: 598 \begin{equation}\label{eq:w_La} 599 w_{*L}= \left(u_*^2 u_{s0}\right)^{1/3}; 600 \end{equation} 601 this is the 602 Where the mixedlayer is stable, a composite velocity scale is assumed: 603 \begin{equation}\label{eq:compositenu} 604 \nu_{\ast}= \left{}u_*^3 \left[\right]1exp(1.5 \mathrm{La}_t^2})\right]+w_{*L}^3\right}^{1/3} 605 \end{equation} 587 606 \subsubsection{The flux gradient model} 588 607 The fluxgradient relationships used in the OSMOSIS scheme take the form,
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