clear 
clear path 
whos
global Nx Ny Nz
global lat long dz dm mdep
global delt_su su_its t_su delt
global descriptor this_path
global f deltaf Q beta r_expt r_heat H
global time rots it
global g Cp rho_bar alpha
global u v t w 
global iterations

XCenter = Nx/2 ;
YCenter = Ny/2 ;
R2 = 55 ;
% create large circular mask
mask=ones(Nx,Ny); 
for i=1:Nx
  for j=1:Ny
    DispX=XCenter-i;
    DispY=YCenter-j;
      if ( DispX^2 + DispY^2 >= R2^2 ) 
        mask(i,j)=0;
      end
  end
end

cmin=-1e-4;
cmax=+1e-4;
V=[cmin cmax];
figure
caxis('manual')
        pcolor(lat,long,squeeze(w(:,:,15)).*mask);shading('interp');
        axis image;caxis(V);colorbar('horizontal');