air_potential_temperature / (K)     (-- : 6; -- : 70; grid_latitude: 100; grid_longitude: 100)
     Dimension coordinates:
          grid_latitude                 -       -                  x                    -
          grid_longitude                -       -                  -                    x
     Auxiliary coordinates:
          level_height                  -       x                  -                    -
          sigma                         -       x                  -                    -
          surface_altitude              -       -                  x                    x
     Derived coordinates:
          altitude                      -       x                  x                    x
     Scalar coordinates:
          forecast_period: 0.0 hours
     Attributes:
          source: Iris test case