Change of dtype due to xarray update

[observingClouds]

The recent release of xarray (v2024.03.0) implemented a more CF conform interpretation of the scale_factor and offset parameters (pydata/xarray#2304). Now the dtype of scale_factor and offset influence the returned dtype.

Some of the tests are impacted by this, in particular those that rely on the air_temperature xarray tutorial dataset:

short air(time=2920, lat=25, lon=53);
  :long_name = "4xDaily Air temperature at sigma level 995";
  :units = "degK";
...
  :actual_range = 185.16f, 322.1f; // float
  :scale_factor = 0.01; // double

Because the scale_factor is double, the returned value is now float64, while previously has been float32.