title: Xarray find maximum value for each grid point across time
body: <p>I have the following netcdf file, which contains daily rainfall (precip) over a region, and I have opened it as an xarray.</p>
  <pre><code>&lt;xarray.Dataset&gt;
  Dimensions:    (latitude: 500, longitude: 600, time: 120)
  Coordinates:
    * latitude   (latitude) float32 -35.22 -35.17 -35.12 ... -10.38 -10.33 -10.28
    * longitude  (longitude) float32 10.27 10.32 10.38 10.43 ... 40.12 40.18 40.22
    * time       (time) datetime64[ns] 2022-01-01 2022-01-02 ... 2022-04-30
  Data variables:
      precip     (time, latitude, longitude) float32 ...
  Attributes: (12/15)
      Conventions:       CF-1.6
      title:             CHIRPS Version 2.0
      history:           created by Climate Hazards Group
      version:           Version 2.0
      date_created:      2022-05-16
      creator_name:      Pete Peterson
      ...                ...
      reference:         Funk, C.C., Peterson, P.J., Landsfeld, M.F., Pedreros,...
      comments:           time variable denotes the first day of the given day....
      acknowledgements:  The Climate Hazards Group InfraRed Precipitation with ...
      ftp_url:           ftp://chg-ftpout.geog.ucsb.edu/pub/org/chg/products/CH...
      website:           http://chg.geog.ucsb.edu/data/chirps/index.html
      faq:               http://chg-wiki.geog.ucsb.edu/wiki/CHIRPS_FAQ
  </code></pre>
  <p>I would like to pull out the maximum precip value at each grid point (i.e. each lat/lon point). I need the maximum value to keep its attributes of latitude, longitude and time because I will then analyse when and where these maximums occurred.</p>
  <p>I know I can use the following to get a maximum value at the first grid point, across time. But how do I then see where this max occurs and on what date?</p>
  <pre><code>ds1a.precip[:,0,0].max()
  </code></pre>
  <p>I am really struggling to then do this for all grid points. I would really appreciate guidance.</p>