function [ts,x,y,z]=extract_levitus_monthly(suff,months,lon_lo,lon_hi,lat_lo,lat_hi)
%
% Extract monthly Levitus data from netcdf files 
%
% e.g.
%   [T,x,y,z]=extract_levitus_monthly('temp',1,-180,180,-90,90);
%   [S,x,y,z]=extract_levitus_monthly('salt',1:12,0,360,-90,90);

% change a name convention:
  if strcmp(suff,'temp'); suff = 'theta'; end
  
  
  ncquiet;
  load DATAPATH datapath
  fname = fullfile(datapath,['levitus_month_' suff '.cdf']);
  theResult=ncload(fname);
  if isempty(theResult);
    error([fname ' not found'])
  end
  
  if size(X,1) > 1; X = X'; end
  if size(Y,1) > 1; Y = Y'; end
  if size(Z,1) > 1; Z = Z'; end
  if size(T,1) > 1; T = T'; end

  i0=round( lon_lo )+1;
  i1=round( lon_hi );
  j0=round( (lat_lo+90) )+1;
  j1=round( (lat_hi+90) );
  
  if i1>i0
    ii=i0:i1;
  else
    ii=[i0:360 1:i1];
  end
  ii=mod(ii+360-1,360)+1;
  jj=j0:j1;
  
  nx=prod(size(ii));
  ny=prod(size(jj));
  
  if strcmp(suff,'theta');
    ts=permute(theta(months,:,jj,ii),[4 3 2 1]);
  elseif strcmp(suff,'salt');
    ts=permute(sal(months,:,jj,ii),[4 3 2 1]);
  else
    error(['unknown variable ' suff])
  end
    
  kk = find(isnan(ts));
  ts(kk) = 0;

  x=X(ii);
  ih = find(x>lon_hi); x(ih)=x(ih)-360;
  il = find(x<lon_lo); x(il)=x(il)+360;
  y=Y(jj);
  z=-Z;

  return