title: How to plot dots over contourf in Python using Basemap lib?
body: <p>I am looking for a simple way to plot dots over certain values in a contourf Basemap plot</p>
  
  <p>Here is an example code:</p>
  
  <pre><code>from mpl_toolkits.basemap import Basemap
  import matplotlib.pyplot as plt
  import numpy as np
  
  dx, dy = 0.5, 0.5
  
  # generate 2 2d grids for the x &amp; y bounds
  y, x = np.mgrid[slice(-15, 15 + dy, dy),
                  slice(-90, -60 + dx, dx)]
  
  z = np.sin(x) + np.cos(5 + y*x) * np.cos(x) + x*y/100
  n, m = z.shape
  z = z - np.exp(np.random.rand(n,m))
  
  #Setup the map
  m = Basemap(projection='merc', llcrnrlat=-15, urcrnrlat=15,\
              llcrnrlon=-90, urcrnrlon=-60, resolution='l')
  m.drawcoastlines()
  
  xx, yy = m(x,y)
  cs = m.contourf(xx,yy,z,cmap=plt.cm.Spectral_r)
  cbar = plt.colorbar(cs, orientation='horizontal', shrink=0.5)
  
  plt.show()
  </code></pre>
  
  <p>I'd like that where <code>a = np.where(abs(z) &gt; 5,np.nan,z)</code> Basemap plots dots just like in the figure attached</p>
  
  <p><img src="https://i.imgur.com/MtUr63c.png" alt="example"></p>