Hello,
I just wanted to check on the usage of the standard name "number_of_days_with_air_temperature_below_threshold" for "frost day" and "ice day" counts. The definition of this standard name implies, I think, that cell_methods should be specified as "time: minimum within days time: sum over days" for frost days and "time: maximum within days time: sum over days". This usage would convey some of the relevant information, but I'm not sure it is consistent with the usage of cell_methods described in the CF standard itself. In the standard it is implied that a variable with cell_methods="time: maximum within days time: sum over days" would be the sum of the daily maxima. Here there is a thresholding operation in between which is omitted from the description only because "threshold" is not an available operation in table e.1.
If "threshold" was added to table e.1 of the standard I suppose that "number_of_days_with_air_temperature_below_threshold" would become redundant and we could use "air_temperature" with cell_methods="time: minimum within days time: threshold within days time: sum over days". This would also allow us to deal with other indices (dry days, windy days) without creating new standard names. An additional attribute would be needed to describe the threshold in some way.
Have I missed something?
Martin
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Received on Thu Aug 08 2013 - 08:40:32 BST
