Quirky issue: checker reports error when units is "years" even if not time

[agstephens]

I have a file which includes a coordinate variable called return_period which happens to have the units of years. The file also contains a valid time coordinate variable. When I run the checker it tells me that there is an error in the definition of my return_period coord variable because it is interpreting it as a time variable.

The error is:

------------------
Checking variable: return_period
------------------
WARN: (4.4.1): Use of the calendar and/or month_lengths attributes is recommended for time coordinate variables
ERROR: (4.4): Invalid units and/or reference time

The relevant snippet from the file looks like:

               float stillWaterReturnLevel(time, return_period, percentile, latitude, longitude) ;
                                stillWaterReturnLevel:_FillValue = 1.e+20f ;
                                stillWaterReturnLevel:units = "m" ;
                double time(time) ;
                                time:axis = "T" ;
                                time:units = "days since 2006-1-1 00:00:00" ;
                                time:standard_name = "time" ;
                                time:long_name = "Time" ;
                                time:calendar = "360_day" ;
                double return_period(return_period) ;
                                return_period:units = "years" ;
                                return_period:long_name = "return_period" ;

I wonder if we should provide a way of telling the checker: "do not interpret this variable as a time variable". Otherwise, I'm not sure how to cope with this issue.

[alexamici]

This happens also for other time units, for example:

        double step(step) ;
		step:long_name = "time since forecast_reference_time" ;
		step:standard_name = "forecast_period" ;
		step:units = "hours" ;