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Changeset 15522 – NEMO

Changeset 15522


Ignore:
Timestamp:
2021-11-18T19:52:07+01:00 (6 months ago)
Author:
amoulin
Message:

Manual updates for wave-coupling interaction - ticket #2744

Location:
NEMO/trunk/doc
Files:
7 edited

Legend:

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  • NEMO/trunk/doc/latex/NEMO/main/bibliography.bib

    r14374 r15522  
    563563} 
    564564 
     565@article{        couvelard_2020, 
     566  author        = "X. Couvelard and F. Lemari{\'e} and G. Samson and J.-L. Redelsperger and F. Ardhuin and R. Benshila and G. Madec", 
     567  doi           = "10.5194/gmd-13-3067-2020", 
     568  journal       = "Geosci. Model Dev", 
     569  month         = "Jul", 
     570  pages         = "3067--3090", 
     571  title         = "Development of a two-way-coupled ocean--wave model: assessment on a global NEMO(v3.6)--WW3(v6.02) coupled configuration", 
     572  volume        = "13", 
     573  year          = "2020", 
     574} 
     575 
    565576@article{         cox_OM87, 
    566577  title         = "Isopycnal diffusion in a z-coordinate ocean model", 
  • NEMO/trunk/doc/latex/NEMO/subfiles/chap_SBC.tex

    r14530 r15522  
    7878  (\np[=.true.]{ln_dm2dc}{ln\_dm2dc}), 
    7979\item the activation of wave effects from an external wave model  (\np[=.true.]{ln_wave}{ln\_wave}), 
    80 \item a neutral drag coefficient is read from an external wave model (\np[=.true.]{ln_cdgw}{ln\_cdgw}), 
    81 \item the Stokes drift from an external wave model is accounted for (\np[=.true.]{ln_sdw}{ln\_sdw}), 
    82 \item the choice of the Stokes drift profile parameterization (\np[=0..2]{nn_sdrift}{nn\_sdrift}), 
    83 \item the surface stress given to the ocean is modified by surface waves (\np[=.true.]{ln_tauwoc}{ln\_tauwoc}), 
    84 \item the surface stress given to the ocean is read from an external wave model (\np[=.true.]{ln_tauw}{ln\_tauw}), 
    85 \item the Stokes-Coriolis term is included (\np[=.true.]{ln_stcor}{ln\_stcor}), 
    86 \item the light penetration in the ocean (\np[=.true.]{ln_traqsr}{ln\_traqsr} with namelist \nam{tra_qsr}{tra\_qsr}), 
     80\item the light penetration in the ocean (\np[=.true.]{ln_traqsr}{ln\_traqsr} with \nam{tra_qsr}{tra\_qsr}), 
    8781\item the atmospheric surface pressure gradient effect on ocean and ice dynamics (\np[=.true.]{ln_apr_dyn}{ln\_apr\_dyn} with namelist \nam{sbc_apr}{sbc\_apr}), 
    8882\item the effect of sea-ice pressure on the ocean (\np[=.true.]{ln_ice_embd}{ln\_ice\_embd}). 
     
    171165 
    172166%\colorbox{yellow}{Penser a} mettre dans le restant l'info nn\_fsbc ET nn\_fsbc*rdt de sorte de reinitialiser la moyenne si on change la frequence ou le pdt 
     167 
    173168 
    174169%% ================================================================================================= 
     
    720715respectively (found in \textit{sbcblk\_skin\_ecmwf.F90}). 
    721716 
     717 
     718 
    722719\subsubsection{COARE 3.x} 
    723720 
     
    906903In this case, CO$_2$ fluxes will be exchanged between the atmosphere and the ice-ocean system 
    907904(and need to be activated in \nam{sbc_cpl}{sbc\_cpl} ). 
     905 
     906 
     907When an external wave model (see \autoref{sec:SBC_wave}) is used in the coupled system, wave parameters, surface currents and sea surface height can be exchanged between both models (and need to be activated in \nam{sbc_cpl}{sbc\_cpl} ). 
     908 
    908909 
    909910The namelist above allows control of various aspects of the coupling fields (particularly for vectors) and 
     
    15721573Ocean waves represent the interface between the ocean and the atmosphere, so \NEMO\ is extended to incorporate 
    15731574physical processes related to ocean surface waves, namely the surface stress modified by growth and 
    1574 dissipation of the oceanic wave field, the Stokes-Coriolis force and the Stokes drift impact on mass and 
    1575 tracer advection; moreover the neutral surface drag coefficient from a wave model can be used to evaluate 
    1576 the wind stress. 
     1575dissipation of the oceanic wave field, the Stokes-Coriolis force, the vortex-force, the Bernoulli head J term and the Stokes drift impact on mass and tracer advection; moreover the neutral surface drag coefficient or the Charnock parameter from a wave model can be used to evaluate the wind stress. NEMO has also been extended to take into account the impact of surface waves on the vertical mixing, via the parameterization of the Langmuir turbulence, the modification of the surface boundary conditions for the Turbulent Kinetic Energy closure scheme, and the inclusion the Stokes drift contribution to the shear production term in different turbulent closure schemes (RIC, TKE, GLS).\\ 
    15771576 
    15781577Physical processes related to ocean surface waves can be accounted by setting the logical variable 
    15791578\np[=.true.]{ln_wave}{ln\_wave} in \nam{sbc}{sbc} namelist. In addition, specific flags accounting for 
    1580 different processes should be activated as explained in the following sections. 
     1579different processes should be activated as explained in the following sections.\\ 
    15811580 
    15821581Wave fields can be provided either in forced or coupled mode: 
    15831582\begin{description} 
    1584 \item [forced mode]: wave fields should be defined through the \nam{sbc_wave}{sbc\_wave} namelist 
     1583\item [forced mode]: the neutral drag coefficient, the two components of the surface Stokes drift, the significant wave height, the mean wave period, the mean wave number, and the normalized 
     1584wave stress going into the ocean can be read from external files. Wave fields should be defined through the \nam{sbc_wave}{sbc\_wave} namelist 
    15851585for external data names, locations, frequency, interpolation and all the miscellanous options allowed by 
    15861586Input Data generic Interface (see \autoref{sec:SBC_input}). 
     1587 
    15871588\item [coupled mode]: \NEMO\ and an external wave model can be coupled by setting \np[=.true.]{ln_cpl}{ln\_cpl} 
    1588 in \nam{sbc}{sbc} namelist and filling the \nam{sbc_cpl}{sbc\_cpl} namelist. 
     1589in \nam{sbc}{sbc} namelist and filling the \nam{sbc_cpl}{sbc\_cpl} namelist. NEMO can receive the significant wave height, the mean wave period ($T0M1$), the mean wavenumber, the Charnock parameter, the neutral drag coefficient, the two components of the surface Stokes drift and the associated transport, the wave to ocean momentum flux, the net wave-supported stress, the Bernoulli head $J$ term and the wave to ocean energy flux term. 
    15891590\end{description} 
     1591 
    15901592 
    15911593%% ================================================================================================= 
     
    15931595\label{subsec:SBC_wave_cdgw} 
    15941596 
    1595 The neutral surface drag coefficient provided from an external data source (\ie\ a wave model), 
    1596 can be used by setting the logical variable \np[=.true.]{ln_cdgw}{ln\_cdgw} in \nam{sbc}{sbc} namelist. 
    1597 Then using the routine \rou{sbcblk\_algo\_ncar} and starting from the neutral drag coefficent provided, 
     1597The neutral surface drag coefficient provided from an external data source (\ie\ forced or coupled wave model), 
     1598can be used by setting the logical variable \np[=.true.]{ln_cdgw}{ln\_cdgw} in \nam{sbc_wave}{sbc\_wave} namelist. 
     1599Then using the routine \rou{sbcblk\_algo\_ncar} and starting from the neutral drag coefficient provided, 
    15981600the drag coefficient is computed according to the stable/unstable conditions of the 
    15991601air-sea interface following \citet{large.yeager_trpt04}. 
    1600  
    1601 %% ================================================================================================= 
    1602 \subsection[3D Stokes Drift (\forcode{ln_sdw} \& \forcode{nn_sdrift})]{3D Stokes Drift (\protect\np{ln_sdw}{ln\_sdw} \& \np{nn_sdrift}{nn\_sdrift})} 
     1602%% ================================================================================================= 
     1603 
     1604 
     1605\subsection[Charnok coefficient from wave model (\forcode{ln_charn})]{ Charnok coefficient from wave model (\protect\np{ln_charn}{ln\_charn})} 
     1606\label{subsec:SBC_wave_charn} 
     1607 
     1608The dimensionless Charnock parameter characterising the sea surface roughness provided from an external wave model, can be used by setting the logical variable \np[=.true.]{ln_charn}{ln\_charn} in \nam{sbc_wave}{sbc\_wave} namelist. Then using the routine \rou{sbcblk\_algo\_ecmwf}, the roughness length that enters the definition of the drag coefficient is computed according to the Charnock parameter depending on the sea state. 
     1609Note that this option is only available in coupled mode.\\ 
     1610 
     1611%% ================================================================================================= 
     1612 
     1613 
     1614\subsection[3D Stokes Drift (\forcode{ln_sdw})]{3D Stokes Drift (\protect\np{ln_sdw}{ln\_sdw}) } 
    16031615\label{subsec:SBC_wave_sdw} 
    16041616 
     
    16281640and its computation quickly becomes expensive as the 2D spectrum must be integrated for each vertical level. 
    16291641To simplify, it is customary to use approximations to the full Stokes profile. 
    1630 Three possible parameterizations for the calculation for the approximate Stokes drift velocity profile 
    1631 are included in the code through the \np{nn_sdrift}{nn\_sdrift} parameter once provided the surface Stokes drift 
    1632 $\mathbf{U}_{st |_{z=0}}$ which is evaluated by an external wave model that accurately reproduces the wave spectra 
    1633 and makes possible the estimation of the surface Stokes drift for random directional waves in 
    1634 realistic wave conditions: 
     1642Two possible parameterizations for the calculation for the approximate Stokes drift velocity profile 
     1643are included in the code once provided the surface Stokes drift $\mathbf{U}_{st |_{z=0}}$ which is evaluated by an external wave model that accurately reproduces the wave spectra and makes possible the estimation of the surface Stokes drift for random directional waves in realistic wave conditions. To evaluate the 3D Stokes drift, the surface Stokes drift (zonal and meridional components), the Stokes transport or alternatively the significant wave height and the mean wave period should be provided either in forced or coupled mode. 
    16351644 
    16361645\begin{description} 
    1637 \item [{\np{nn_sdrift}{nn\_sdrift} = 0}]: exponential integral profile parameterization proposed by 
    1638 \citet{breivik.janssen.ea_JPO14}: 
     1646\item [By default (\forcode{ln_breivikFV_2016=.true.})]:\\  
     1647An exponential integral profile parameterization proposed by \citet{breivik.janssen.ea_JPO14} is used: 
    16391648 
    16401649\[ 
     
    16471656\[ 
    16481657  % \label{eq:SBC_wave_sdw_0b} 
    1649   k_e = \frac{|\mathbf{U}_{\left.st\right|_{z=0}}|} {|T_{st}|} 
     1658  k_e = \frac{|\mathbf{U}_{\left.st\right|_{z=0}}|} {5.97|T_{st}|} 
    16501659  \quad \text{and }\ 
    16511660  T_{st} = \frac{1}{16} \bar{\omega} H_s^2 
    16521661\] 
    16531662 
    1654 where $H_s$ is the significant wave height and $\omega$ is the wave frequency. 
    1655  
    1656 \item [{\np{nn_sdrift}{nn\_sdrift} = 1}]: velocity profile based on the Phillips spectrum which is considered to be a 
    1657 reasonable estimate of the part of the spectrum mostly contributing to the Stokes drift velocity near the surface 
    1658 \citep{breivik.bidlot.ea_OM16}: 
     1663where $H_s$ is the significant wave height and $\bar{\omega}$ is the wave frequency defined as: $\bar{\omega}=\frac{2\pi}{T_m}$ (being $T_m$ the mean wave period). 
     1664 
     1665\item [If \forcode{ln_breivikFV_2016= .true.} ]: \\ 
     1666 
     1667A velocity profile based on the Phillips spectrum which is considered to be a reasonable estimate of the part of the spectrum mostly contributing to the Stokes drift velocity near the surface \citep{breivik.bidlot.ea_OM16} is used: 
    16591668 
    16601669\[ 
     
    16641673\] 
    16651674 
    1666 where $erf$ is the complementary error function and $k_p$ is the peak wavenumber. 
    1667  
    1668 \item [{\np{nn_sdrift}{nn\_sdrift} = 2}]: velocity profile based on the Phillips spectrum as for \np{nn_sdrift}{nn\_sdrift} = 1 
    1669 but using the wave frequency from a wave model. 
     1675where $erf$ is the complementary error function , $ \beta =1$ and $k_p$ is the peak wavenumber defined as: 
     1676\[ 
     1677  % \label{eq:SBC_wave_kp} 
     1678  k_p = \frac{|\mathbf{U}_{\left.st\right|_{z=0}}|}{2 |T_{st}| } (1-2 \beta /3)  
     1679\] 
     1680 
     1681$|T_{st}|$ is estimated from integral wave parameters (Hs and Tm) in forced mode and is provided directly from an external wave model in coupled mode.  
    16701682 
    16711683\end{description} 
    16721684 
    16731685The Stokes drift enters the wave-averaged momentum equation, as well as the tracer advection equations 
    1674 and its effect on the evolution of the sea-surface height ${\eta}$ is considered as follows: 
    1675  
    1676 \[ 
    1677   % \label{eq:SBC_wave_eta_sdw} 
    1678   \frac{\partial{\eta}}{\partial{t}} = 
    1679   -\nabla_h \int_{-H}^{\eta} (\mathbf{U} + \mathbf{U}_{st}) dz 
    1680 \] 
     1686and its effect on the evolution of the sea-surface height ${\eta}$ by including the barotropic Stokes transport horizontal divergence in the term $D$ of Eq.\ref{eq:MB_ssh} 
    16811687 
    16821688The tracer advection equation is also modified in order for Eulerian ocean models to properly account 
     
    16991705in a force equal to $\mathbf{U}_{st}$×$f$, where $f$ is the Coriolis parameter. 
    17001706This additional force may have impact on the Ekman turning of the surface current. 
    1701 In order to include this term, once evaluated the Stokes drift (using one of the 3 possible 
     1707In order to include this term, once evaluated the Stokes drift (using one of the 2 possible 
    17021708approximations described in \autoref{subsec:SBC_wave_sdw}), 
    17031709\np[=.true.]{ln_stcor}{ln\_stcor} has to be set. 
    17041710 
    17051711%% ================================================================================================= 
    1706 \subsection[Wave modified stress (\forcode{ln_tauwoc} \& \forcode{ln_tauw})]{Wave modified sress (\protect\np{ln_tauwoc}{ln\_tauwoc} \& \np{ln_tauw}{ln\_tauw})} 
    1707 \label{subsec:SBC_wave_tauw} 
     1712 
     1713%% ================================================================================================= 
     1714\subsection[Vortex-force term (\forcode{ln_vortex_force})]{Vortex-force term (\protect\np{ln_vortex_force}{ln\_vortex\_force})} 
     1715\label{subsec:SBC_wave_vf} 
     1716 
     1717The vortex-force term arises from the interaction of the mean flow vorticity with the Stokes drift.  
     1718It results in a force equal to $\mathbf{U}_{st}$×$\zeta$, where $\zeta$ is the mean flow vorticity. 
     1719In order to include this term, once evaluated the Stokes drift (using one of the 2 possible 
     1720approximations described in \autoref{subsec:SBC_wave_sdw}), \np[=.true.]{ln_vortex_force}{ln\_vortex\_force} has to be set. 
     1721 
     1722%% ================================================================================================= 
     1723 
     1724%% ================================================================================================= 
     1725\subsection[Wave-induced pressure term (\forcode{ln_bern_srfc})]{ Wave-induced pressure term (\protect\np{ln_bern_srfc}{ln\_bern\_srfc})} 
     1726\label{subsec:SBC_wave_bhd} 
     1727An adjustment in the mean pressure arises to accommodate for the presence of waves. 
     1728The mean pressure is corrected adding a depth-uniform wave-induced kinematic pressure term named Bernoulli head $J$ term. The Bernoulli head $J$ term is provided to NEMO from an external wave model where it is defined as: 
     1729\[ 
     1730  % \label{eq:SBC_wave_tauw} 
     1731  J = g \iint {\frac{k}{sinh(2kd)} S(k,\theta) d\theta dk} 
     1732\] 
     1733with $d$ the water depth. \\ 
     1734In order to include this term, \np[=.true.]{ln_bern_srfc}{ln\_bern\_srfc} has to be defined as well as the Stokes drift option (\autoref{subsec:SBC_wave_sdw}) and the coupling with an external wave model (\autoref{sec:SBC_wave}). 
     1735 
     1736%% ================================================================================================= 
     1737 
     1738 
     1739\subsection[Wave modified stress (\forcode{ln_tauoc} \& \forcode{ln_taw})]{Wave modified stress (\protect\np{ln_tauoc}{ln\_tauoc} \& \np{ln_taw}{ln\_taw})} 
     1740\label{subsec:SBC_wave_taw} 
    17081741 
    17091742The surface stress felt by the ocean is the atmospheric stress minus the net stress going 
     
    17201753\] 
    17211754 
    1722 where $\tau_a$ is the atmospheric surface stress; 
    1723 $\tau_w$ is the atmospheric stress going into the waves defined as: 
     1755where $\tau_a$ is the atmospheric surface stress; $\tau_w$ is the atmospheric stress going into the waves defined as: 
    17241756 
    17251757\[ 
    17261758  % \label{eq:SBC_wave_tauw} 
    1727   \tau_w = \rho g \int {\frac{dk}{c_p} (S_{in}+S_{nl}+S_{diss})} 
     1759  \tau_w = \rho g \int_{0}^{2\pi} \int {\frac{1}{c_p} (S_{in}+S_{nl}+S_{diss})}dkd\theta 
    17281760\] 
     1761 
     1762%% ∫2π0∫∞0kω(Sin+Sds) dωdθ 
    17291763 
    17301764where: $c_p$ is the phase speed of the gravity waves, 
    17311765$S_{in}$, $S_{nl}$ and $S_{diss}$ are three source terms that represent 
    1732 the physics of ocean waves. The first one, $S_{in}$, describes the generation 
    1733 of ocean waves by wind and therefore represents the momentum and energy transfer 
    1734 from air to ocean waves; the second term $S_{nl}$ denotes 
    1735 the nonlinear transfer by resonant four-wave interactions; while the third term $S_{diss}$ 
    1736 describes the dissipation of waves by processes such as white-capping, large scale breaking 
    1737 eddy-induced damping. 
    1738  
    1739 The wave stress derived from an external wave model can be provided either through the normalized 
    1740 wave stress into the ocean by setting \np[=.true.]{ln_tauwoc}{ln\_tauwoc}, or through the zonal and 
    1741 meridional stress components by setting \np[=.true.]{ln_tauw}{ln\_tauw}. 
     1766the physics of ocean waves. The first one, $S_{in}$, describes the generation of ocean waves by wind and therefore represents the momentum and energy transfer from air to ocean waves; the second term $S_{nl}$ denotes 
     1767the nonlinear transfer by resonant four-wave interactions; while the third term $S_{diss}$ describes the dissipation of waves by processes such as white-capping, large scale breaking eddy-induced damping. Note that the $S_{nl}$ is not always taken into account for the calculation of the atmospheric stress going into the waves, depending on the external wave model. 
     1768The wave stress derived from an external wave model can be provided either through the normalized wave stress into the ocean by setting \np[=.true.]{ln_tauoc}{ln\_tauoc}, or through the zonal and meridional stress components by setting 
     1769 \np[=.true.]{ln_taw}{ln\_taw} .  In coupled mode both options can be used while in forced mode only the first option is included. 
     1770  
     1771If the normalized wave stress into the ocean ($\widetilde{\tau}$) is provided (\np[=.true.]{ln_tauoc}{ln\_tauoc}) the atmospheric stress felt by the ocean circulation is expressed as: 
     1772\[ 
     1773  % \label{eq:SBC_wave_tauoc} 
     1774  \tau_{oc,a} = \tau_a \times \widetilde{\tau} 
     1775\] 
     1776 
     1777If  \np[=.true.]{ln_taw}{ln\_taw} , the zonal and meridional stress fields components from the coupled wave model have to be sent directly to u-grid and v-grid through OASIS. 
     1778 
     1779 
     1780%% ================================================================================================= 
     1781 
     1782\subsection[Waves impact vertical mixing  (\forcode{ln_phioc} \& \forcode{ln_stshear})]{Waves impact vertical mixing (\protect\np{ln_phioc}{ln\_phioc} \& \protect\np{ln_stshear}{ln\_stshear})} 
     1783\label{subsec:SBC_wave_TKE} 
     1784 
     1785 
     1786The vortex-force vertical term gives rise to extra terms in the turbulent kinetic energy (TKE) prognostic \citep{couvelard_2020}. The first term corresponds to a modification of the shear production term.  
     1787The Stokes Drift shear contribution can be included, in coupled mode, by setting \np[=.true.]{ln_stshear}{ln\_stshear}. 
     1788 
     1789 
     1790In addition, waves affect the surface boundary condition for the turbulent kinetic energy, the mixing length scale and the dissipative length scale of the TKE closure scheme. 
     1791The injection of turbulent kinetic energy at the surface can be given by the dissipation of the wave field usually dominated by wave breaking. 
     1792 
     1793In coupled mode, the wave to ocean energy flux term from an external wave model ($ \Phi_o $) can be provided to NEMO and then converted into an ocean turbulence source by setting \np[=.true.]{ln_phioc}{ln\_phioc}. 
     1794The boundary condition for the turbulent kinetic energy is implemented in the \rou{zdftke} as a Dirichlet or as a Neumann boundary condition (see \autoref{subsubsec:ZDF_tke_waveco}). The boundary condition for the mixing length scale and the dissipative length scale can also account for surface waves (see \autoref{subsubsec:ZDF_tke_waveco}) 
     1795 
     1796Some improvements are introduced in the Langmuir turbulence parameterization (see \autoref{chap:ZDF} \autoref{subsubsec:ZDF_tke_langmuir}) if wave coupled mode is activated. 
    17421797 
    17431798%% ================================================================================================= 
  • NEMO/trunk/doc/latex/NEMO/subfiles/chap_ZDF.tex

    r14530 r15522  
    278278 
    279279%% ================================================================================================= 
    280 \subsubsection{Surface wave breaking parameterization} 
     280\subsubsection{Surface wave breaking parameterization (No information from an external wave model)} 
     281\label{subsubsec:ZDF_tke_wave}  
    281282 
    282283Following \citet{mellor.blumberg_JPO04}, the TKE turbulence closure model has been modified to 
     
    306307with $e_{bb}$ the \np{rn_ebb}{rn\_ebb} namelist parameter, setting \np[=67.83]{rn_ebb}{rn\_ebb} corresponds 
    307308to $\alpha_{CB} = 100$. 
    308 Further setting  \np[=.true.]{ln_mxl0}{ln\_mxl0},  applies \autoref{eq:ZDF_Lsbc} as the surface boundary condition on the length scale, 
    309 with $\beta$ hard coded to the Stacey's value. 
    310 Note that a minimal threshold of \np{rn_emin0}{rn\_emin0}$=10^{-4}~m^2.s^{-2}$ (namelist parameters) is applied on the 
    311 surface $\bar{e}$ value. 
     309 
     310Further setting  \np[=.true.]{ln_mxl0}{ln\_mxl0},  applies \autoref{eq:ZDF_Lsbc} as the surface boundary condition on the length scale, with $\beta$ hard coded to the Stacey's value. Note that a minimal threshold of \np{rn_emin0}{rn\_emin0}$=10^{-4}~m^2.s^{-2}$ (namelist parameters) is applied on the surface $\bar{e}$ value.\\ 
     311 
     312\subsubsection{Surface wave breaking parameterization (using information from an external wave model)} 
     313\label{subsubsec:ZDF_tke_waveco}  
     314 
     315Surface boundary conditions for the turbulent kinetic energy, the mixing length scale and the dissipative length scale can be defined using wave fields provided from an external wave model (see \autoref{chap:SBC}, \autoref{sec:SBC_wave}).  
     316The injection of turbulent kinetic energy at the surface can be given by the dissipation of the wave field usually dominated by wave breaking. In coupled mode, the wave to ocean energy flux term ($\Phi_o$) from an external wave model can be provided and then converted into an ocean turbulence source by setting ln\_phioc=.true. 
     317 
     318The surface TKE can be defined by a Dirichlet boundary condition setting $nn\_bc\_surf=0$ in \nam{zdf}{tke} namelist: 
     319\begin{equation} 
     320  \bar{e}_o  = \frac{1}{2}\,\left( 15.8 \, \frac{\Phi_o}{\rho_o}\right) ^{2/3} 
     321\end{equation} 
     322 
     323Nevertheless, due to the definition of the computational grid, the TKE flux is not applied at the free surface but at the centre of the topmost grid cell ($z = z1$). To be more accurate, a Neumann boundary condition amounting to interpreter the half-grid cell at the top as a constant flux layer (consistent with the surface layer Monin–Obukhov theory) can be applied setting $nn\_bc\_surf=1$ in  \nam{zdf}{tke} namelist \citep{couvelard_2020}: 
     324 
     325\begin{equation} 
     326  \left(\frac{Km}{e_3}\,\partial_k e \right)_{z=z1} = \frac{\Phi_o}{\rho_o} 
     327\end{equation} 
     328 
     329 
     330The mixing length scale surface value $l_0$ can be estimated from the surface roughness length z0: 
     331\begin{equation} 
     332  l_o = \kappa \, \frac{ \left( C_k\,C_\epsilon \right) ^{1/4}}{C_k}\, z0 
     333\end{equation} 
     334where $z0$ is directly estimated from the significant wave height ($Hs$) provided by the external wave model as $z0=1.6Hs$. To use this option ln\_mxhsw as well as ln\_wave and ln\_sdw have to be set to .true. 
    312335 
    313336%% ================================================================================================= 
    314337\subsubsection{Langmuir cells} 
     338\label{subsubsec:ZDF_tke_langmuir} 
    315339 
    316340Langmuir circulations (LC) can be described as ordered large-scale vertical motions in 
     
    335359\] 
    336360where $w_{LC}(z)$ is the vertical velocity profile of LC, and $H_{LC}$ is the LC depth. 
    337 With no information about the wave field, $w_{LC}$ is assumed to be proportional to 
    338 the Stokes drift $u_s = 0.377\,\,|\tau|^{1/2}$, where $|\tau|$ is the surface wind stress module 
    339 \footnote{Following \citet{li.garrett_JMR93}, the surface Stoke drift velocity may be expressed as 
    340   $u_s =  0.016 \,|U_{10m}|$. 
    341   Assuming an air density of $\rho_a=1.22 \,Kg/m^3$ and a drag coefficient of 
    342   $1.5~10^{-3}$ give the expression used of $u_s$ as a function of the module of surface stress 
    343 }. 
     361 
    344362For the vertical variation, $w_{LC}$ is assumed to be zero at the surface as well as at 
    345363a finite depth $H_{LC}$ (which is often close to the mixed layer depth), 
     
    349367  w_{LC}  = 
    350368  \begin{cases} 
    351     c_{LC} \,u_s \,\sin(- \pi\,z / H_{LC} )    &      \text{if $-z \leq H_{LC}$}    \\ 
     369    c_{LC} \,\|u_s^{LC}\| \,\sin(- \pi\,z / H_{LC} )    &      \text{if $-z \leq H_{LC}$}    \\ 
    352370    0                             &      \text{otherwise} 
    353371  \end{cases} 
    354372\] 
    355 where $c_{LC} = 0.15$ has been chosen by \citep{axell_JGR02} as a good compromise to fit LES data. 
    356 The chosen value yields maximum vertical velocities $w_{LC}$ of the order of a few centimeters per second. 
     373 
     374 
     375In the absence of information about the wave field, $w_{LC}$ is assumed to be proportional to 
     376the surface Stokes drift ($u_s^{LC}=u_{s0} $) empirically estimated by $ u_{s0} = 0.377\,\,|\tau|^{1/2}$, where $|\tau|$ is the surface wind stress module 
     377\footnote{Following \citet{li.garrett_JMR93}, the surface Stoke drift velocity may be expressed as 
     378  $u_{s0} =  0.016 \,|U_{10m}|$. 
     379  Assuming an air density of $\rho_a=1.22 \,Kg/m^3$ and a drag coefficient of 
     380  $1.5~10^{-3}$ give the expression used of $u_{s0}$ as a function of the module of surface stress 
     381}. 
     382 
     383In case of online coupling with an external wave model (see \autoref{chap:SBC} \autoref{sec:SBC_wave}), $w_{LC}$ is proportional to the component of the Stokes drift aligned with the wind \citep{couvelard_2020} and $ u_s^{LC}  = \max(u_{s0}.e_\tau,0)$ where $e_\tau$ is the unit vector in the wind stress direction and $u_{s0}$ is the surface Stokes drift provided by the external wave model. 
     384 
     385 
     386$c_{LC} = 0.15$ has been chosen by \citep{axell_JGR02} as a good compromise to fit LES data. 
     387The chosen value yields maximum vertical velocities $w_{LC}$ of the order of a few centimetres per second. 
    357388The value of $c_{LC}$ is set through the \np{rn_lc}{rn\_lc} namelist parameter, 
    358389having in mind that it should stay between 0.15 and 0.54 \citep{axell_JGR02}. 
     
    362393converting its kinetic energy to potential energy, according to 
    363394\[ 
    364 - \int_{-H_{LC}}^0 { N^2\;z  \;dz} = \frac{1}{2} u_s^2 
     395- \int_{-H_{LC}}^0 { N^2\;z  \;dz} = \frac{1}{2} \|u_s^{LC}\|^2 
    365396\] 
    366397 
     
    14271458the Stokes Drift can be evaluated by setting \forcode{ln_sdw=.true.} 
    14281459(see \autoref{subsec:SBC_wave_sdw}) 
    1429 and the needed wave fields can be provided either in forcing or coupled mode 
     1460and the needed wave fields (significant wave height and mean wave number) can be provided either in forcing or coupled mode 
    14301461(for more information on wave parameters and settings see \autoref{sec:SBC_wave}) 
    14311462 
  • NEMO/trunk/doc/namelists/namsbc

    r11005 r15522  
    3333   ln_isf      = .false.   !  ice shelf                                 (T   => fill namsbc_isf & namsbc_iscpl) 
    3434   ln_wave     = .false.   !  Activate coupling with wave  (T => fill namsbc_wave) 
    35    ln_cdgw     = .false.   !  Neutral drag coefficient read from wave model (T => ln_wave=.true. & fill namsbc_wave) 
    36    ln_sdw      = .false.   !  Read 2D Surf Stokes Drift & Computation of 3D stokes drift (T => ln_wave=.true. & fill namsbc_wave)  
    37    nn_sdrift   =  0        !  Parameterization for the calculation of 3D-Stokes drift from the surface Stokes drift 
    38       !                    !   = 0 Breivik 2015 parameterization: v_z=v_0*[exp(2*k*z)/(1-8*k*z)] 
    39       !                    !   = 1 Phillips:                      v_z=v_o*[exp(2*k*z)-beta*sqrt(-2*k*pi*z)*erfc(sqrt(-2*k*z))] 
    40       !                    !   = 2 Phillips as (1) but using the wave frequency from a wave model 
    41    ln_tauwoc   = .false.   !  Activate ocean stress modified by external wave induced stress (T => ln_wave=.true. & fill namsbc_wave) 
    42    ln_tauw     = .false.   !  Activate ocean stress components from wave model 
    43    ln_stcor    = .false.   !  Activate Stokes Coriolis term (T => ln_wave=.true. & ln_sdw=.true. & fill namsbc_wave) 
    4435   nn_lsm      = 0         !  =0 land/sea mask for input fields is not applied (keep empty land/sea mask filename field) , 
    4536                           !  =1:n number of iterations of land/sea mask application for input fields (fill land/sea mask filename field) 
  • NEMO/trunk/doc/namelists/namsbc_cpl

    r13472 r15522  
    4848   sn_rcv_isf    =   'none'                 ,    'no'    ,     ''      ,         ''           ,   '' 
    4949   sn_rcv_icb    =   'none'                 ,    'no'    ,     ''      ,         ''           ,   '' 
    50    sn_rcv_tauwoc =   'none'                 ,    'no'    ,     ''      ,         ''          ,   '' 
    51    sn_rcv_tauw   =   'none'                 ,    'no'    ,     ''      ,         ''          ,   '' 
    52    sn_rcv_wdrag  =   'none'                 ,    'no'    ,     ''      ,         ''          ,   '' 
     50   sn_rcv_wdrag  =   'none'                 ,    'no'    ,     ''      ,         ''           ,   '' 
     51   sn_rcv_charn  =   'none'                 ,    'no'    ,     ''      ,         ''           ,   '' 
     52   sn_rcv_taw    =   'none'                 ,    'no'    ,     ''      ,         ''           ,   'U,V' 
     53   sn_rcv_bhd    =   'none'                 ,    'no'    ,     ''      ,         ''           ,   '' 
     54   sn_rcv_tusd   =   'none'                 ,    'no'    ,     ''      ,         ''           ,   '' 
     55   sn_rcv_tvsd   =   'none'                 ,    'no'    ,     ''      ,         ''           ,   '' 
    5356/ 
  • NEMO/trunk/doc/namelists/namsbc_wave

    r11703 r15522  
    22&namsbc_wave   ! External fields from wave model                        (ln_wave=T) 
    33!----------------------------------------------------------------------- 
     4   ln_sdw      = .false.       !  get the 2D Surf Stokes Drift & Compute the 3D stokes drift 
     5   ln_stcor    = .false.       !  add Stokes Coriolis and tracer advection terms 
     6   ln_cdgw     = .false.       !  Neutral drag coefficient read from wave model 
     7   ln_tauoc    = .false.       !  ocean stress is modified by wave induced stress 
     8   ln_wave_test= .false.       !  Test case with constant wave fields 
     9! 
     10   ln_charn    = .false.       !  Charnock coefficient read from wave model (IFS only) 
     11   ln_taw      = .false.       !  ocean stress is modified by wave induced stress (coupled mode) 
     12   ln_phioc    = .false.       !  TKE flux from wave model 
     13   ln_bern_srfc= .false.       !  wave induced pressure. Bernoulli head J term 
     14   ln_breivikFV_2016 = .false. !  breivik 2016 vertical stokes profile 
     15   ln_vortex_force = .false.   !  Vortex Force term 
     16   ln_stshear  = .false.       !  include stokes shear in EKE computation 
     17! 
    418   cn_dir      = './'      !  root directory for the waves data location 
    519   !___________!_________________________!___________________!___________!_____________!________!___________!__________________!__________!_______________! 
     
    1125   sn_hsw      =  'sdw_ecwaves_orca2'    ,        6.         , 'hs'         ,  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
    1226   sn_wmp      =  'sdw_ecwaves_orca2'    ,        6.         , 'wmp'        ,  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
    13    sn_wfr      =  'sdw_ecwaves_orca2'    ,        6.         , 'wfr'        ,  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
    1427   sn_wnum     =  'sdw_ecwaves_orca2'    ,        6.         , 'wave_num'   ,  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
    15    sn_tauwoc   =  'sdw_ecwaves_orca2'    ,        6.         , 'wave_stress',  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
    16    sn_tauwx    =  'sdw_ecwaves_orca2'    ,        6.         , 'wave_stress',  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
    17    sn_tauwy    =  'sdw_ecwaves_orca2'    ,        6.         , 'wave_stress',  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
     28   sn_tauoc    =  'sdw_ecwaves_orca2'    ,        6.         , 'wave_stress',  .true.  , .true. , 'yearly'  ,  ''              , ''       , '' 
    1829/ 
  • NEMO/trunk/doc/namelists/namzdf_tke

    r13472 r15522  
    3030   !                       !           = 2 weighted by 1-fr_i 
    3131   !                       !           = 3 weighted by 1-MIN(1,4*fr_i) 
     32   nn_bc_surf   =     1    !  surface condition (0/1=Dir/Neum) ! Only applicable for wave coupling (ln_cplwave=1) 
     33   nn_bc_bot    =     1    !  bottom condition (0/1=Dir/Neum) ! Only applicable for wave coupling (ln_cplwave=1) 
    3234/ 
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