Dear Jonathan > Thanks for your email and sorry for another long delay in this correspondence > (two months this time). My slowness indicates that although this discussion is > useful and thought-provoking, I don't really have enough time to pursue it, > unfortunately; I am holding up progress. I am not so optimistic that the trac system would help us. I have a new idea and may be we must not change the cell methods. To open the cell method for structering should be a more general approach. With my last proposal I would strech it to much. We would change the units of the physical quantity with these cell methods and I do not fully reconsider the consequences. If possible I would like to avoid this. > Perhaps the best way to take this > forward, if you would like to, would be for you to make specific proposals as > a trac ticket for amendment to CF, when you are ready, and I hope that others > will then comment. > I am not so optimistic that the trac system would help us. I have a new idea and may be we must not change the cell methods. To open the cell method for structuring should be a more general approach. With my last proposal I would stretch it to much. We would change the units of the physical quantity with these cell methods and I do not fully reconsider the consequences. If possible I would like to avoid this. > You are, I think, suggesting an addition to cell_methods for a number_of_days > standard name, to indicate whether the condition is that the quantity (air > temperature etc.) should be below or above the threshold. That idea has more > general applicability than these statistical indices, and I think it's a good > use of cell_methods. > That was not all. We need an indicator function. > If a standard_name has the phrase "dependent_on_X" (or whatever phrase is > used) it would mean that it must have a coordinate variable, scalar coordinate > variable or auxiliary coordinate variable with standard_name of X, to specify > the condition. >
This gives me a new idea: /* number of days with daily minimum below 0 degC = frost_days = fd (IPCC AR4 and AR5) */ float n1(lat,lon); n1:standard_name="number_of_days_with_variable_below_threshold"; n1:coordinates="threshold time"; n1:cell_methods="time: sum over days"; float threshold; threshold:standard_name="air_temperature"; threshold:units="degC"; threshold:cell_methods="time:minimun within days" data: threshold=0.; The threshold with the term "below_threshold" describes the indicator condition. The term "number_of_days_with" describes the sum over the indicator value. Is this possible ? If yes we need also number_of_days_with_variable_above_threshold I like the term "threshold". This was your or Alison's proposal. Other examples for this would be: summer days max>25 degC tropical nights min>20 degC ice days max<0 degC frost days where no snow with threshold:standard_name="lwe_thickness_of_precipitation_amount" heavy precipitation >10 mm = r10 (IPCC AR4 and AR5) very heavy precipitation >20 mm wet days > 1mm with threshold:standard_name="wind_speed" strong breeze days max > 10,5 m/s strong gale days max > 20,5 m/s hurricane days max > 32,5 m/s These are only the simple statistic indices but it is a start. What do you think ? Could we use the scalar coordinate this way ? Best wishes Heinke _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
