air_potential_temperature / (K)     (model_level_number: 70; grid_latitude: 100; grid_longitude: 100)
    Dimension coordinates:
        model_level_number                             x                  -                    -
        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
        time                        2009-09-09 17:10:00
    Attributes:
        source                      'Iris test case'