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'