Changeset 6320


Ignore:
Timestamp:
2016-02-17T16:24:34+01:00 (5 years ago)
Author:
mathiot
Message:

ISF: update documentation

Location:
trunk/DOC/TexFiles
Files:
6 edited

Legend:

Unmodified
Added
Removed
  • trunk/DOC/TexFiles/Biblio/Biblio.bib

    r6289 r6320  
    12621262  pages = {1081--1098}, 
    12631263} 
     1264 
    12641265@ARTICLE{Griffies_Hallberg_MWR00, 
    12651266  author = {S.M. Griffies and R.H. Hallberg}, 
     
    15141515} 
    15151516 
     1517@TechReport{Hunter2006, 
     1518  Title                    = {Specification for Test Models of Ice Shelf Cavities}, 
     1519  Author                   = {J. R. Hunter}, 
     1520  Institution              = {Antarctic Climate \& Ecosystems Cooperative Research Centre Private Bag 80, Hobart, Tasmania 7001}, 
     1521  Year                     = {2006}, 
     1522} 
     1523 
    15161524@TECHREPORT{TEOS10, 
    15171525  author = {IOC and SCOR and IAPSO}, 
     
    15941602  volume = {96},  number = {C11}, 
    15951603  pages = {2298--2312} 
     1604} 
     1605 
     1606@ARTICLE{Jenkins2001, 
     1607  author = {A. Jenkins}, 
     1608  title = {The Role of Meltwater Advection in the Formulation of Conservative Boundary Conditions at an Ice-Ocean Interface}, 
     1609  journal = JPO, 
     1610  year = {2001}, 
     1611  volume = {31}, 
     1612  pages = {285--296} 
    15961613} 
    15971614 
  • trunk/DOC/TexFiles/Chapters/Chap_DOM.tex

    r6289 r6320  
    495495in each water column is by-passed}.  
    496496If \np{ln\_isfcav}~=~true, an extra file input file describing the ice shelf draft  
    497 (in meters) (\ifile{isf\_draft\_meter}) is needed and all the location where the isf cavity thinnest 
    498  than \np{rn\_isfhmin} meters are grounded ($i.e.$ masked).  
     497(in meters) (\ifile{isf\_draft\_meter}) is needed. 
    499498 
    500499After reading the bathymetry, the algorithm for vertical grid definition differs  
     
    539538domain width at the central latitude. This is meant for the "EEL-R5" configuration,  
    540539a periodic or open boundary channel with a seamount.  
    541 \item[\np{nn\_bathy} = 1] read a bathymetry. The \ifile{bathy\_meter} file (Netcdf format)  
    542 provides the ocean depth (positive, in meters) at each grid point of the model grid.  
    543 The bathymetry is usually built by interpolating a standard bathymetry product  
     540\item[\np{nn\_bathy} = 1] read a bathymetry and ice shelf draft (if needed). 
     541 The \ifile{bathy\_meter} file (Netcdf format) provides the ocean depth (positive, in meters) 
     542 at each grid point of the model grid. The bathymetry is usually built by interpolating a standard bathymetry product  
    544543($e.g.$ ETOPO2) onto the horizontal ocean mesh. Defining the bathymetry also  
    545544defines the coastline: where the bathymetry is zero, no model levels are defined  
    546545(all levels are masked). 
     546 
     547The \ifile{isfdraft\_meter} file (Netcdf format) provides the ice shelf draft (positive, in meters) 
     548 at each grid point of the model grid. This file is only needed if \np{ln\_isfcav}~=~true.  
     549Defining the ice shelf draft will also define the ice shelf edge and the grounding line position. 
    547550\end{description} 
    548551 
     
    601604(Fig.~\ref{Fig_zgr}). 
    602605 
     606If the ice shelf cavities are opened (\np{ln\_isfcav}=~true~}), the definition of $z_0$ is the same.  
     607However, definition of $e_3^0$ at $t$- and $w$-points is respectively changed to: 
     608\begin{equation} \label{DOM_zgr_ana} 
     609\begin{split} 
     610 e_3^T(k) &= z_W (k+1) - z_W (k)   \\ 
     611 e_3^W(k) &= z_T (k)   - z_T (k-1) \\ 
     612\end{split} 
     613\end{equation} 
     614This formulation decrease the self-generated circulation into the ice shelf cavity  
     615(which can, in extreme case, leads to blow up).\\ 
     616 
     617  
    603618The most used vertical grid for ORCA2 has $10~m$ ($500~m)$ resolution in the  
    604619surface (bottom) layers and a depth which varies from 0 at the sea surface to a  
     
    865880gives the number of ocean levels ($i.e.$ those that are not masked) at each  
    866881$t$-point. mbathy is computed from the meter bathymetry using the definiton of  
    867 gdept as the number of $t$-points which gdept $\leq$ bathy.  
     882gdept as the number of $t$-points which gdept $\leq$ bathy. 
    868883 
    869884Modifications of the model bathymetry are performed in the \textit{bat\_ctl}  
     
    871886that do not communicate with another ocean point at the same level are eliminated. 
    872887 
    873 From the \textit{mbathy} array, the mask fields are defined as follows: 
     888In case of ice shelf cavities, as for the representation of bathymetry, a 2D integer array, misfdep, is created.  
     889misfdep defines the level of the first wet $t$-point (ie below the ice-shelf/ocean interface). All the cells between $k=1$ and $misfdep(i,j)-1$ are masked.  
     890By default, $misfdep(:,:)=1$ and no cells are masked. 
     891Modifications of the model bathymetry and ice shelf draft into  
     892the cavities are performed in the \textit{zgr\_isf} routine. The compatibility between ice shelf draft and bathymetry is checked.  
     893All the locations where the isf cavity is thinnest than \np{rn\_isfhmin} meters are grounded ($i.e.$ masked).  
     894If only one cell on the water column is opened at $t$-, $u$- or $v$-points, the bathymetry or the ice shelf draft is dug to fit this constrain. 
     895If the incompatibility is too strong (need to dig more than 1 cell), the cell is masked.\\  
     896 
     897From the \textit{mbathy} and \textit{misfdep} array, the mask fields are defined as follows: 
    874898\begin{align*} 
    875 tmask(i,j,k) &= \begin{cases}   \; 1&   \text{ if $k\leq mbathy(i,j)$  }    \\ 
    876                                                 \; 0&   \text{ if $k\leq mbathy(i,j)$  }    \end{cases}     \\ 
     899tmask(i,j,k) &= \begin{cases}   \; 0&   \text{ if $k < misfdep(i,j) $ } \\ 
     900                                \; 1&   \text{ if $misfdep(i,j) \leq k\leq mbathy(i,j)$  }    \\ 
     901                                \; 0&   \text{ if $k > mbathy(i,j)$  }    \end{cases}     \\ 
    877902umask(i,j,k) &=         \; tmask(i,j,k) \ * \ tmask(i+1,j,k)   \\ 
    878903vmask(i,j,k) &=         \; tmask(i,j,k) \ * \ tmask(i,j+1,k)   \\ 
    879904fmask(i,j,k) &=         \; tmask(i,j,k) \ * \ tmask(i+1,j,k)   \\ 
    880                    & \ \ \, * tmask(i,j,k) \ * \ tmask(i+1,j,k) 
     905                   & \ \ \, * tmask(i,j,k) \ * \ tmask(i+1,j,k) \\ 
     906wmask(i,j,k) &=         \; tmask(i,j,k) \ * \ tmask(i,j,k-1) \text{ with } wmask(i,j,1) = tmask(i,j,1)  
    881907\end{align*} 
    882908 
    883 Note that \textit{wmask} is not defined as it is exactly equal to \textit{tmask} with  
    884 the numerical indexing used (\S~\ref{DOM_Num_Index}). Moreover, the  
    885 specification of closed lateral boundaries requires that at least the first and last  
     909Note, wmask is now defined. It allows, in case of ice shelves,  
     910to deal with the top boundary (ice shelf/ocean interface) exactly in the same way as for the bottom boundary.  
     911 
     912The specification of closed lateral boundaries requires that at least the first and last  
    886913rows and columns of the \textit{mbathy} array are set to zero. In the particular  
    887914case of an east-west cyclical boundary condition, \textit{mbathy} has its last  
  • trunk/DOC/TexFiles/Chapters/Chap_DYN.tex

    r6289 r6320  
    654654pressure Jacobian method is used to solve the horizontal pressure gradient. This method can provide 
    655655a more accurate calculation of the horizontal pressure gradient than the standard scheme. 
     656 
     657\subsection{Ice shelf cavity} 
     658\label{DYN_hpg_isf} 
     659Beneath an ice shelf, the total pressure gradient is the sum of the pressure gradient due to the ice shelf load and 
     660 the pressure gradient due to the ocean load. If cavity opened (\np{ln\_isfcav}~=~true) these 2 terms can be 
     661 calculated by setting \np{ln\_dynhpg\_isf}~=~true. No other scheme are working with the ice shelf.\\ 
     662 
     663$\bullet$ The main hypothesis to compute the ice shelf load is that the ice shelf is in an isostatic equilibrium. 
     664 The top pressure is computed integrating from surface to the base of the ice shelf a reference density profile  
     665(prescribed as density of a water at 34.4 PSU and -1.9$\degres C$) and corresponds to the water replaced by the ice shelf.  
     666This top pressure is constant over time. A detailed description of this method is described in \citet{Losch2008}.\\ 
     667 
     668$\bullet$ The ocean load is computed using the expression \eqref{Eq_dynhpg_sco} described in \ref{DYN_hpg_sco}.  
    656669 
    657670%-------------------------------------------------------------------------------------------------------------- 
  • trunk/DOC/TexFiles/Chapters/Chap_SBC.tex

    r6289 r6320  
    5151\item the modification of fluxes below ice-covered areas (using observed ice-cover or a sea-ice model) (\np{nn\_ice}~=~0,1, 2 or 3) ;  
    5252\item the addition of river runoffs as surface freshwater fluxes or lateral inflow (\np{ln\_rnf}~=~true) ;  
    53 \item the addition of isf melting as lateral inflow (parameterisation) (\np{nn\_isf}~=~2 or 3 and \np{ln\_isfcav}~=~false)  
    54 or as fluxes applied at the land-ice ocean interface (\np{nn\_isf}~=~1 or 4 and \np{ln\_isfcav}~=~true) ;  
     53\item the addition of isf melting as lateral inflow (parameterisation) or as fluxes applied at the land-ice ocean interface (\np{ln\_isf}) ;  
    5554\item the addition of a freshwater flux adjustment in order to avoid a mean sea-level drift (\np{nn\_fwb}~=~0,~1~or~2) ;  
    5655\item the transformation of the solar radiation (if provided as daily mean) into a diurnal cycle (\np{ln\_dm2dc}~=~true) ;  
     
    924923\namdisplay{namsbc_isf} 
    925924%-------------------------------------------------------------------------------------------------------- 
    926 Namelist variable in \ngn{namsbc}, \np{nn\_isf}, control the kind of ice shelf representation used.  
     925Namelist variable in \ngn{namsbc}, \np{nn\_isf}, controls the ice shelf representation used.  
    927926\begin{description} 
    928927\item[\np{nn\_isf}~=~1] 
    929 The ice shelf cavity is represented. The fwf and heat flux are computed. 2 bulk formulations are available:  
    930 the ISOMIP one (\np{nn\_isfblk = 1}) described in (\np{nn\_isfblk = 2}),  
    931 the 3 equation formulation described in \citet{Jenkins1991}.  
    932 In addition to this, 3 different ways to compute the exchange coefficient are available.  
    933 $\gamma\_{T/S}$ is constant (\np{nn\_gammablk = 0}), $\gamma\_{T/S}$ is velocity dependant  
    934 \citep{Jenkins2010} (\np{nn\_gammablk = 1}) and $\gamma\_{T/S}$ is velocity dependant  
    935 and stratification dependent \citep{Holland1999} (\np{nn\_gammablk = 2}).  
    936 For each of them, the thermal/salt exchange coefficient (\np{rn\_gammat0} and \np{rn\_gammas0})  
    937 have to be specified (the default values are for the ISOMIP case).  
    938 Full description, sensitivity and validation in preparation.  
     928The ice shelf cavity is represented (\np{ln\_isfcav}~=~true needed). The fwf and heat flux are computed. Two different bulk formula are available: 
     929   \begin{description} 
     930   \item[\np{nn\_isfblk}~=~1] 
     931   The bulk formula used to compute the melt is based the one described in \citet{Hunter2006}. 
     932        This formulation is based on a balance between the upward ocean heat flux and the latent heat flux at the ice shelf base. 
     933 
     934   \item[\np{nn\_isfblk}~=~2]  
     935   The bulk formula used to compute the melt is based the one described in \citet{Jenkins1991}. 
     936        This formulation is based on a 3 equations formulation (a heat flux budget, a salt flux budget 
     937         and a linearised freezing point temperature equation). 
     938   \end{description} 
     939 
     940For this 2 bulk formulations, there are 3 different ways to compute the exchange coeficient: 
     941   \begin{description} 
     942        \item[\np{nn\_gammablk~=~0~}] 
     943   The salt and heat exchange coefficients are constant and defined by \np{rn\_gammas0} and \np{rn\_gammat0} 
     944 
     945   \item[\np{nn\_gammablk~=~1~}] 
     946   The salt and heat exchange coefficients are velocity dependent and defined as $\np{rn\_gammas0} \times u_{*}$ and $\np{rn\_gammat0} \times u_{*}$ 
     947        where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters). 
     948        See \citet{Jenkins2010} for all the details on this formulation. 
     949    
     950   \item[\np{nn\_gammablk~=~2~}] 
     951   The salt and heat exchange coefficients are velocity and stability dependent and defined as  
     952        $\gamma_{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}}$ 
     953        where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn\_hisf\_tbl} meters),  
     954        $\Gamma_{Turb}$ the contribution of the ocean stability and  
     955        $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 
     956        See \citet{Holland1999} for all the details on this formulation. 
     957        \end{description} 
    939958 
    940959\item[\np{nn\_isf}~=~2] 
     
    942961The fwf is distributed along the ice shelf edge between the depth of the average grounding line (GL) 
    943962(\np{sn\_depmax\_isf}) and the base of the ice shelf along the calving front (\np{sn\_depmin\_isf}) as in (\np{nn\_isf}~=~3).  
    944 Furthermore the fwf is computed using the \citet{Beckmann2003} parameterisation of isf melting.  
    945 The effective melting length (\np{sn\_Leff\_isf}) is read from a file and the exchange coefficients  
    946 are set as (\np{rn\_gammat0}) and (\np{rn\_gammas0}). 
     963Furthermore the fwf and heat flux are computed using the \citet{Beckmann2003} parameterisation of isf melting.  
     964The effective melting length (\np{sn\_Leff\_isf}) is read from a file. 
    947965 
    948966\item[\np{nn\_isf}~=~3] 
    949967A simple parameterisation of isf is used. The ice shelf cavity is not represented.  
    950 The fwf (\np{sn\_rnfisf}) is distributed along the ice shelf edge between the depth of the average grounding line (GL) 
    951 (\np{sn\_depmax\_isf}) and the base of the ice shelf along the calving front (\np{sn\_depmin\_isf}). 
    952 Full description, sensitivity and validation in preparation. 
     968The fwf (\np{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between the depth of the average grounding line (GL) 
     969(\np{sn\_depmax\_isf}) and the base of the ice shelf along the calving front (\np{sn\_depmin\_isf}).  
     970The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 
    953971 
    954972\item[\np{nn\_isf}~=~4] 
    955 The ice shelf cavity is represented. However, the fwf (\np{sn\_fwfisf}) and heat flux (\np{sn\_qisf}) are  
    956 not computed but specified from file.  
     973The ice shelf cavity is opened (\np{ln\_isfcav}~=~true needed). However, the fwf is not computed but specified from file \np{sn\_fwfisf}).  
     974The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$.\\ 
    957975\end{description} 
    958976 
    959 \np{nn\_isf}~=~1 and \np{nn\_isf}~=~2 compute a melt rate based on the water masse properties, ocean velocities and depth. 
    960  This flux is thus highly dependent of the model resolution (horizontal and vertical), realism of the water masse onto the shelf ... 
    961  
    962 \np{nn\_isf}~=~3 and \np{nn\_isf}~=~4 read the melt rate and heat flux from a file. You have total control of the fwf scenario. 
    963  
     977 
     978$\bullet$ \np{nn\_isf}~=~1 and \np{nn\_isf}~=~2 compute a melt rate based on the water mass properties, ocean velocities and depth. 
     979 This flux is thus highly dependent of the model resolution (horizontal and vertical), realism of the water masses onto the shelf ...\\ 
     980 
     981 
     982$\bullet$ \np{nn\_isf}~=~3 and \np{nn\_isf}~=~4 read the melt rate from a file. You have total control of the fwf forcing. 
    964983This can be usefull if the water masses on the shelf are not realistic or the resolution (horizontal/vertical) are too  
    965 coarse to have realistic melting or for sensitivity studies where you want to control your input.  
    966 Full description, sensitivity and validation in preparation.  
    967  
    968 \np{rn\_hisf\_tbl} is the top boundary layer (tbl) thickness used by the Losch parametrisation \citep{Losch2008} to compute the melt. if 0, temperature/salt/velocity in the top cell is used to compute the melt. 
    969 Otherwise, NEMO used the mean value into the tbl.  
     984coarse to have realistic melting or for studies where you need to control your heat and fw input.\\  
     985 
     986A namelist parameters control over how many meters the heat and fw fluxes are spread.  
     987\np{rn\_hisf\_tbl}] is the top boundary layer thickness as defined in \citet{Losch2008}.  
     988This parameter is only used if \np{nn\_isf}~=~1 or \np{nn\_isf}~=~4 
     989 
     990If \np{rn\_hisf\_tbl} = 0.0, the fluxes are put in the top level whatever is its tickness.  
     991 
     992If \np{rn\_hisf\_tbl} $>$ 0.0, the fluxes are spread over the first \np{rn\_hisf\_tbl} m (ie over one or several cells).\\ 
     993 
     994The ice shelf melt is implemented as a volume flux with in the same way as for the runoff. 
     995The fw addition due to the ice shelf melting is, at each relevant depth level, added to the horizontal divergence  
     996(\textit{hdivn}) in the subroutine \rou{sbc\_isf\_div}, called from \mdl{divcur}.  
     997See the runoff section \ref{SBC_rnf} for all the details about the divergence correction.  
     998 
    970999 
    9711000\section{ Ice sheet coupling} 
  • trunk/DOC/TexFiles/Chapters/Chap_TRA.tex

    r6289 r6320  
    734734(see \S\ref{SBC_rnf} for further detail of how it acts on temperature and salinity tendencies) 
    735735 
     736$\bullet$ \textit{fwfisf}, the mass flux associated with ice shelf melt, (see \S\ref{SBC_isf} for further details  
     737on how the ice shelf melt is computed and applied). 
     738 
    736739The surface boundary condition on temperature and salinity is applied as follows: 
    737740\begin{equation} \label{Eq_tra_sbc} 
     
    13821385                   I've changed "derivative" to "difference" and "mean" to "average"} 
    13831386 
    1384 With partial bottom cells (\np{ln\_zps}=true), in general, tracers in horizontally  
     1387With partial cells (\np{ln\_zps}=true) at bottom and top (\np{ln\_isfcav}=true), in general, tracers in horizontally  
    13851388adjacent cells live at different depths. Horizontal gradients of tracers are needed  
    13861389for horizontal diffusion (\mdl{traldf} module) and for the hydrostatic pressure  
    1387 gradient (\mdl{dynhpg} module) to be active.  
     1390gradient (\mdl{dynhpg} module) to be active. The partial cell properties  
     1391at the top (\np{ln\_isfcav}=true) are computed in the same way as for the bottom. So, only the bottom interpolation is shown. 
    13881392\gmcomment{STEVEN from gm : question: not sure of  what -to be active- means} 
     1393 
    13891394Before taking horizontal gradients between the tracers next to the bottom, a linear  
    13901395interpolation in the vertical is used to approximate the deeper tracer as if it actually  
  • trunk/DOC/TexFiles/Chapters/Chap_ZDF.tex

    r6289 r6320  
    842842% Bottom Friction 
    843843% ================================================================ 
    844 \section  [Bottom and top Friction (\textit{zdfbfr})]   {Bottom Friction (\mdl{zdfbfr} module)} 
     844\section  [Bottom and Top Friction (\textit{zdfbfr})]   {Bottom and Top Friction (\mdl{zdfbfr} module)} 
    845845\label{ZDF_bfr} 
    846846 
     
    850850 
    851851Options to define the top and bottom friction are defined through the  \ngn{nambfr} namelist variables. 
    852 The top friction is activated only if the ice shelf cavities are opened (\np{ln\_isfcav}~=~true). 
    853 As the friction processes at the top and bottom are the represented similarly, only the bottom friction is described in detail. 
     852The bottom friction represents the friction generated by the bathymetry.  
     853The top friction represents the friction generated by the ice shelf/ocean interface.  
     854As the friction processes at the top and bottom are represented similarly, only the bottom friction is described in detail below.\\ 
     855 
    854856 
    855857Both the surface momentum flux (wind stress) and the bottom momentum  
Note: See TracChangeset for help on using the changeset viewer.