title: How to extract coordinates from where the variable meets a criterion for a netCDF dataset with Python and xarray?
body: <p>I have a xarray DataArray object <code>da_criteria_daily</code> where are generated from a netCDF file.</p>
  
  <pre><code>&lt;xarray.DataArray (time: 365, latitude: 106, longitude: 193)&gt;
  dask.array&lt;shape=(365, 106, 193), dtype=bool, chunksize=(1, 106, 193)&gt;
  Coordinates:
    * time       (time) datetime64[ns] 2017-01-01 2017-01-02 ... 2017-12-31
    * latitude   (latitude) float32 -39.2 -39.149525 ... -33.950478 -33.9
    * longitude  (longitude) float32 140.8 140.84792 140.89584 ... 149.95209 150.0
  </code></pre>
  
  <p>It's a daily data over a year for a geographic extent. The variable is a Boolean type.</p>
  
  <p>I would like to get all coordinates (latitude, longitude) values for a particular date where the variable is True.</p>
  
  <pre><code>new_da = da_criteria_daily.where(da_criteria_daily==True, drop=True)
  print(new_da)
  </code></pre>
  
  <p>I got:</p>
  
  <pre><code>&lt;xarray.DataArray (time: 161, latitude: 106, longitude: 193)&gt;
  dask.array&lt;shape=(161, 106, 193), dtype=float64, chunksize=(1, 106, 193)&gt;
  Coordinates:
    * time       (time) datetime64[ns] 2017-01-01 2017-01-02 ... 2017-12-31
    * latitude   (latitude) float32 -39.2 -39.149525 ... -33.950478 -33.9
    * longitude  (longitude) float32 140.8 140.84792 140.89584 ... 149.95209 150.0
  </code></pre>
  
  <p>Are you any functions with xarray.DataArray that can be used to retrieve coordinates from variables?</p>