Make a Variable's Valid Data Range Consistent Within Each Product Release

Recommendation Details: There are cases of published Earth Science data products with valid data ranges for some variables (specified via the CF valid_min  and valid_max attributes, or via the CF valid_range attribute) that vary file-to-file, based on the actual data range for each particular variable within each particular product file - we do not agree with this approach.

The valid data range for each variable in an Earth Science data product should be made consistent within each product release, and should not vary file-to-file within a given product release.

The valid data range for any given variable should be based upon the relevant physics for that variable, and, possibly, constraints placed upon the variable based on the characteristics of the sensor(s) that collected the data.  The relevant physics should not vary file-to-file.  The characteristics of the sensor(s) can change with time, in which case we recommend that the widest valid data range consistent with the changing characteristics of the sensors(s) be used for each variable within a given product release.

We note that the choice of the valid data range for any given variable places a constraint on the choice of the fill value for that variable, because the fill value must be a number outside of the valid data range (as explained in a separate recommendation).