Hello Vergand, One of my jobs is running a parameter vocabulary that currently has over 27,000 entries. Much of its bulk is due to the assignment of multiple parameter names for each step in a numeric sequence - such as radiation wavelengths or sediment grain-size expressed as percentiles.
Consider a scenario where you start with a small group of standard percentiles - say 5, 25, 50, 75, 95. You set up a parameter name for each of these in the first instance, which is easy. Then along comes another user who wants to describe data with percentiles at a resolution of 1 per cent. So another 95 parameter names need to be set up. Then along comes another user who wants a resolution of 0.1 per cent. I start drowning in names and nobody can find anything. However, had I followed Jonathan's second solution all I would need to do as a vocabulary manager is set up one concept to describe the percentile axis, which covers every user from those who use a handful of percentiles to those whose percentile resolution requirements are beyond the bounds of my imagination. I know Jonathan's first option was based on propogation of cell methods and not standard names. However, these still need managing and if they become excessively abundant they also become difficult to navigate. Cheers, Roy. ________________________________________ From: Vegard Bønes [vegard.bo...@met.no] Sent: 15 November 2011 13:17 To: Lowry, Roy K. Cc: cf-metadata@cgd.ucar.edu; Jonathan Gregory Subject: Re: [CF-metadata] standards for probabilities Dear Roy, Can you be a bit more concrete about why you prefer the second alternative? -- Vegard ----- Original Message ----- Fra: "Roy K. Lowry" <r...@bodc.ac.uk> Til: "Jonathan Gregory" <j.m.greg...@reading.ac.uk>, "Vegard B??nes" <vegard.bo...@met.no> Kopi: cf-metadata@cgd.ucar.edu Sendt: 15. november 2011 11:17:01 Emne: RE: [CF-metadata] standards for probabilities Dear Jonathan, I prefer your second alternative. It's not what I do, but it's what I wish I did!! Cheers, Roy. ________________________________________ From: cf-metadata-boun...@cgd.ucar.edu [cf-metadata-boun...@cgd.ucar.edu] On Behalf Of Jonathan Gregory [j.m.greg...@reading.ac.uk] Sent: 15 November 2011 10:11 To: Vegard B??nes Cc: cf-metadata@cgd.ucar.edu Subject: Re: [CF-metadata] standards for probabilities Dear Vegard > I want to express such things as "25th percentile precipitation amount" > (based on ensemble data), and probability that air temperature will be within > 2.5 degrees of the forecast. How should I do this? You are right, this case has not yet been dealt with, although the guidelines for construction of standard names foresee that needs like this might arise! If the quantity is a precipitation_amount, it's fine to use that standard name. The question is how to record that is the 25th percentile. Two possible ways to do this would be: * To extend the possible syntax of cell_methods so that it can describe percentiles. It is already possible to indicate a median in cell_methods, and that is a particular percentile. The advantage of this way of doing it would be that you would record whether the distribution of precipitation amounts being considered was for time-variation, or spatial variation, or some other kind of variation. Obviously you could have a probability distribution with percentiles for many different independent variables. * To use a size-1 or scalar coordinate variable to record the probability, with a new standard_name, perhaps cumulative_distribution_function_of_precipitation_amount. The value of this coordinate would be 0.25 for the 25th percentile. The advantage of this method would be that you could have several different percentiles in the same variable, by having a multivalued probability coord. If you wanted to be specific about what the independent variable was, that would have to be included in the standard name as well e.g. cumulative_distribution_function_of_precipitation_amount_over_time. What do you think? Cheers Jonathan _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata-- This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system. _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
