title: Xarray: Setting common name for two coordinates which physically belong to the same dimension
body: <p>Sorry in advance for the unhelpful title, but I couldn't come up with a good short description of what I'm asking.</p>
  <p>It's common for data in fluid dynamics applications to have coordinates of the following way:</p>
  <pre><code>&lt;xarray.Dataset&gt;
  Dimensions:  (time: 4, yC: 5, yF: 5)
  Coordinates:
    * yF       (yF) float64 0.0 0.4883 0.9766 1.465 1.953
    * yC       (yC) float64 0.2441 0.7324 1.221 1.709 2.197
    * time     (time) float64 0.1146 1.031 1.948 2.406
  Data variables:
      ω_x      (time, yF) float64 dask.array&lt;chunksize=(4, 5), meta=np.ndarray&gt;
      w        (time, yC) float64 dask.array&lt;chunksize=(4, 5), meta=np.ndarray&gt;
  </code></pre>
  <p>Note that two of the dimensions (<code>yC</code> and <code>yF</code>) have staggered values. This is because they are both values of the physical dimension <code>y</code>. They are, however, staggered just like the figure below (taken from the <code>xgcm</code> package docs):</p>
  <p><a href="https://i.stack.imgur.com/j2vkKl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/j2vkKl.png" alt="enter image description here" /></a></p>
  <p>Is there any way to tell <code>xarray</code> that these two dimensions are actually the same? So that I could possibly do</p>
  <pre><code>ds.ω_x.plot(y='y') # instead of ds.ω_x.plot(y='yF')
  ds.w.plot(y='y') # instead of ds.w.plot(y='yC')
  </code></pre>
  <p>and it would work as expected?</p>