Dear Jonathan First of all, regarding propositions for new standard names: It is likely that as a result of this discussion, I will propose some new standard names and name modifiers. But please don't consider any of my ideas here as formal standards propositions.
Now, regarding probabilities of values within a given range: When we say precipitation_probability we really mean probability that each value will be within an absolute range given in variable x. And when we say air_temperature_confidence we really mean probability that each value will be within a range given in variable x, relative to an air_temperature variable. These are two very different things, and I believe that they should be treated as such. For air temperature, I believe that using bounds is not the way to go. There must be some kind of link to the reported temperature. Therefore, I believe that a variable air_temperature confidence with an extra dimension interval_of_air_temperature is better. Regarding precipitation, bounds seem to do better. But I am not happy about the fact that there must be an artificial upper boundary for precipitation. Also, I am not sure if bounds are intended to be used with overlapping ranges? I am uncertain about what is best then – to use bounds with very high upper limit, or to use my original approach – to create a new standard_name: limit_of_precipitation_amount, and use it as a dimension to precipitation_amount confidence. Any further thoughts? -- Vegard ----- Original Message ----- Fra: "Jonathan Gregory" <[email protected]> Til: [email protected] Sendt: 2. desember 2011 11:10:20 Emne: Re: [CF-metadata] standards for probabilities Dear Vegard > A dimension (and variable) for specifying percentiles: > float percentile(percentile) ; > percentile:units = "1" ; > percentile:standard_name = "cumulative_distribution_function" > ; > float air_temperature_percentiles(time, percentile, latitude, > longitude) ; > air_temperature_percentiles:units = "K" ; > air_temperature_percentiles:standard_name = "air_temperature" > ; This looks sensible to me. Are you proposing cumulative_distribution_function as a new standard name? > ...an alternative for percentile could be > cumulative_distribution_function_over_realization. Yes. That would be more informative, and therefore preferable, I think. > Then, there is the problem of certainty that a temperature will be within a > given range. Could you do that like this: float air_temperature(air_temperature); air_temperature:bounds="air_temperature_bounds"; air_temperature:units="K"; float air_temperature_bounds(air_temperature,2); float air_temperature_confidence(time,air_temperature,latitude,longitude); air_temperature_confidence:standard_name="probability"; Then the air_temperature_bounds specify the ranges of air temperature for which the probability is evaluated. probability would be a new standard name as well. Again it could be made more informative as something like probability_over_realization. This is instead of a standard_name modifier and seems more consistent to me with the treatment of percentile. It is a kind of transpose. > Also, which I did not mention in the previous emails, I also wanted to > express the probability of at least x mm of precipitation. This can be done in the same way as the probability of air temperature ranges, with the upper bounds for precipitation ranges set high enough that they are effectively infinite. > When working with this, I found that expressing percentiles and > probabilities as dimensions, instead of attributes, made the relationship > between them more intuitive. I agree. Cheers Jonathan _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
