title: I want my contourf semi-transparent, but my colorbar not
body: <p>The colorbar takes the same transparency as the contourf-plot which I've placed over an image.</p>
  
  <p>I can achieve a non-transparent colorbar by adding a fake contourf plot without transparency at the lowest "zorder"-location, but I guess there is a proper way?</p>
  
  <p>This gives me a semi-transparent colorbar:</p>
  
  <pre><code>cs = m.contourf(xv,yv,zi,zorder=4,alpha=0.7,origin="lower")
  cbar = m.colorbar(cs,location='right',pad="5%")
  </code></pre>