title: Numpy Adding two vectors with different sizes
body: <p>If I have two numpy arrays of different sizes, how can I superimpose them.</p>
  
  <pre><code>a = numpy([0, 10, 20, 30])
  b = numpy([20, 30, 40, 50, 60, 70])
  </code></pre>
  
  <p>What is the cleanest way to add these two vectors to produce a new vector (20, 40, 60, 80, 60, 70)?</p>
  
  <p>This is my generic question. For background, I am specifically applying a Green's transform function and need to superimpose the results for each time step in the evaulation unto the responses previously accumulated.</p>