title: How to perform a bilinear interpolation for an area
body: <p>I have a netCDF File which shows surface runoff from 1850 to 2014. I took a slice to show the runoff in a specific area, and the resulting plot gives me four regions which may have different runoff values, depending on the date. I wanted to use bilinear interpolation to find the runoff at the point 282,43.5.
  How would I set up the code to do this?
  What I have so far is:</p>
  <pre><code>file='D:\\mrros_Eday_IPSL-CM6A-LR_land-hist_r1i1p1f1_gr_18500101-20141231.nc'
  
  dset = xr.open_dataset(file, decode_times=True, use_cftime=True)
  latbounds = (42,45) # (min, max)
  lonbounds = (280, 282.5) # (min, max)
  
  #lets say i take the plot at this particular date
  dset['mrros'].sel(time=cftime.DatetimeGregorian(1850, 7, 22, 12, 0, 0, 0),lat=slice(*latbounds),lon=slice(*lonbounds)).plot()
  plt.show()
  
  array=dset['mrros'].sel(time=cftime.DatetimeGregorian(1850, 7, 22, 12, 0, 0, 0),lat=slice(*latbounds),lon=slice(*lonbounds))
  #I can see the runoff values of each section but how would I use this too take a binomial interpolation.
  </code></pre>