function status=write_mask(Gname,rmask,umask,vmask,pmask);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Hernan G. Arango %%%%
% Copyright (c) 2001 Rutgers University.                               %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                      %
% function status=write_mask(Gname,rmask,umask,vmask,pmask)            %
%                                                                      %
% This routine writes out mask data into GRID NetCDF file.             %
%                                                                      %
% On Input:                                                            %
%                                                                      %
%    Gname       GRID NetCDF file name (character string).             %
%    rmask       Land/Sea mask on RHO-points (real matrix):            %
%                  rmask=0 land, rmask=1 Sea.                          %
%    umask       Land/Sea mask on U-points (real matrix):              %
%                  umask=0 land, umask=1 Sea.                          %
%    vmask       Land/Sea mask on V-points (real matrix):              %
%                  vmask=0 land, vmask=1 Sea.                          %
%    pmask       Land/Sea mask on PSI-points (real matrix):            %
%                  pmask=0 land, pmask=1 Sea.                          %
%                                                                      %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%-----------------------------------------------------------------------
% Inquire grid NetCDF file about mask variables.
%-----------------------------------------------------------------------

got.pmask=0;  define.pmask=1;  Vname.pmask='mask_psi';
got.rmask=0;  define.rmask=1;  Vname.rmask='mask_rho';
got.umask=0;  define.umask=1;  Vname.umask='mask_u';
got.vmask=0;  define.vmask=1;  Vname.vmask='mask_v';

[varnam,nvars]=nc_vname(Gname);
for n=1:nvars,
  name=deblank(varnam(n,:));
  switch name
    case {Vname.pmask}
      got.pmask=1;
      define.pmask=0;
    case {Vname.rmask}
      got.rmask=1;
      define.rmask=0;
    case {Vname.umask}
      got.umask=1;
      define.umask=0;
    case {Vname.vmask}
      got.vmask=1;
      define.vmask=0;
  end,
end,

%-----------------------------------------------------------------------
%  If appropriate, define Land/Sea mask variables.
%-----------------------------------------------------------------------

if (define.pmask | define.rmask | define.umask | define.pmask),

%  Inquire about dimensions.

  Dname.xp='xi_psi';    Dname.yp='eta_psi';
  Dname.xr='xi_rho';    Dname.yr='eta_rho';
  Dname.xu='xi_u';      Dname.yu='eta_u';
  Dname.xv='xi_v';      Dname.yv='eta_v';

  [Dnames,Dsizes]=nc_dim(Gname);
  ndims=length(Dsizes);
  for n=1:ndims,
    dimid=n;
    name=deblank(Dnames(n,:));
    switch name
      case {Dname.xp}
        Dsize.xp=Dsizes(n);
        did.xp=dimid;
      case {Dname.yp}
        Dsize.yp=Dsizes(n);
        did.yp=dimid;
      case {Dname.xr}
        Dsize.xr=Dsizes(n);
        did.xr=dimid;
      case {Dname.yr}
        Dsize.yr=Dsizes(n);
        did.yr=dimid;
      case {Dname.xu}
        Dsize.xu=Dsizes(n);
        did.xu=dimid;
      case {Dname.yu}
        Dsize.yu=Dsizes(n);
        did.yu=dimid;
      case {Dname.xv}
        Dsize.xv=Dsizes(n);
        did.xv=dimid;
      case {Dname.yr}
        Dsize.yv=Dsizes(n);
        did.yv=dimid;
    end,
  end,

%  Define NetCDF parameters.

  [ncglobal]=mexcdf('parameter','nc_global');
  [ncdouble]=mexcdf('parameter','nc_double');
  [ncfloat]=mexcdf('parameter','nc_float');
  [ncchar]=mexcdf('parameter','nc_char');

%  Open GRID NetCDF file.

  [ncid]=mexcdf('ncopen',Gname,'nc_write');
  if (ncid == -1),
    error(['WRITE_MASK: ncrefdef - unable to open file: ', Gname]);
    return
  end,


%  Put GRID NetCDF file into define mode.

  [status]=mexcdf('ncredef',ncid);
  if (status == -1),
    error(['WRITE_MASK: ncrefdef - unable to put into define mode.']);
    return
  end,

%  Define Land/Sea mask on RHO-points.

  if (define.rmask),
    Var.name =Vname.rmask;
    Var.type =ncdouble;
    Var.dimid=[did.yr did.xr];
    Var.long ='mask on RHO-points';
    Var.opt_0='land';
    Var.opt_1='sea';
    Var.units='nondimensional';

    [varid,status]=nc_vdef(ncid,Var);
    clear Var
  end,

%  Define Land/Sea mask on PSI-points.

  if (define.pmask),
    Var.name =Vname.pmask;
    Var.type =ncdouble;
    Var.dimid=[did.yp did.xp];
    Var.long ='mask on PSI-points';
    Var.opt_0='land';
    Var.opt_1='sea';
    Var.units='nondimensional';

    [varid,status]=nc_vdef(ncid,Var);
    clear Var
  end,

%  Define Land/Sea mask on U-points.

  if (define.umask),
    Var.name =Vname.umask;
    Var.type =ncdouble;
    Var.dimid=[did.yu did.xu];
    Var.long ='mask on U-points';
    Var.opt_0='land';
    Var.opt_1='sea';
    Var.units='nondimensional';

    [varid,status]=nc_vdef(ncid,Var);
    clear Var
  end,

%  Define Land/Sea mask on V-points.

  if (define.vmask),
    Var.name =Vname.vmask;
    Var.type =ncdouble;
    Var.dimid=[did.yv did.xv];
    Var.long ='mask on V-points';
    Var.opt_0='land';
    Var.opt_1='sea';
    Var.units='nondimensional';

    [varid,status]=nc_vdef(ncid,Var);
    clear Var
  end,

%  Leave definition mode.

  [status]=mexcdf('ncendef',ncid);
  if (status == -1),
    error(['WRITE_MASK: ncendef - unable to leave definition mode.']);
  end,

%  Close GRID NetCDF file.

  [status]=mexcdf('ncclose',ncid);
  if (status == -1),
    error(['WRITE_MASK: ncclose - unable to close NetCDF file: ', Gname]);
  end,

end,

%-----------------------------------------------------------------------
%  Write out mask data into GRID NetCDF file.
%-----------------------------------------------------------------------

[status]=nc_write(Gname,Vname.rmask,rmask);
[status]=nc_write(Gname,Vname.pmask,pmask);
[status]=nc_write(Gname,Vname.umask,umask);
[status]=nc_write(Gname,Vname.vmask,vmask);

return