function [h]=stereo_map(field,lon,lat,clon,clat,radius,nc,colorbar_pos,colorbar_legend,contour);
% []=stereo_map(field,lon,lat,clon,clat,radius,colorbar_pos,colorbar_legend,contour);
%
%    Mapping 2D flieds onto a sphere using Stereographic Projection
%           [opt]   overlays positive and minus contours as white (solid/dashed)  
%
%    Imputs :
%                -  field ( nx by ny ) 
%                -  lon   (nx)
%                -  lat   (ny)
%                -  clon, clat : coordinates of view point
%                - nc : number of countours (13 or 17 recommended)
%                -  colorbar_pos 'vert' or 'horiz'  
%                -  colorbar_legend e.g. 'Political stupidity (#Republicans/m^2)''
%                -  contour : '1 or 0 
%  
%   Hepta Techonlogies , Sept 2006   
%   
%    Reference :   http://www.eos.ubc.ca/~rich/map.html#3._Stereographic_projection_of_North
%    
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

S.U=field;
S.X=lon;
S.Y=lat;
make_periodic('S','X');
[M,m]=maxmin(S.U);
L=max([-m,M]);
ci=linspace(-L,L,nc);
m_proj('stereographic','lat',clat,'long',clon,'radius',radius)
m_proj('ortho','lat',clat,'long',clon);
%
[cs,h]=m_contourf(S.X,S.Y,S.U,ci); colormap(cejulien2(nc));  hold on
caxis([-L,L]);
m_coast('line', 'color',[0 0 0],'LineWidth', [2], 'LineStyle', '-'); hold on
m_grid('xtick',12, 'linest','-','YaxisLocation','right', 'FontSize', 9);
colorbar3(colorbar_pos,colorbar_legend); hold on; caxis([-L,L]);
if (contour==1)
   [cspm,hpm]=m_contourpm_white(S.X,S.Y,S.U,ci); hold off
end