Dear Jim Karl's suggestion of how to encode the bounds looks correct to me, and I don't think an extension is needed unless there is a definite need to record that some of the first and last seasons are missing. As I said before, it's not obvious to me why this is a greater problem than the possibility of any of the other seasons (not the first and last) being missing in calculating the mean. There is no standardised method for recording missing data within the interval when any cell_method is calculated. This applies in all cases, not just for climatological time. It is possible to make a note in () in the cell_methods. If a standardised method is definitely needed by some use-cases, then I think we should reopen the possibility of recording the coordinates before the cell_ method was applied, because this would be a general method for addressing the issue, and has already come up more than once in other discussions.
Best wishes Jonathan ----- Forwarded message from Jim Biard <[email protected]> ----- > Date: Tue, 16 Feb 2016 08:32:41 -0500 > From: Jim Biard <[email protected]> > To: [email protected] > Subject: Re: [CF-metadata] How to build CF-compliant seasonal climatology > when data begins within a season > User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) > Gecko/20100101 Thunderbird/38.5.1 > > Hi, > > So, it sounds like there is a need to extend the conventions to > account for this issue. > > As a suggestion, how about specifying the climatological bounds > (either as Karl originally described or keeping the dates all within > the full time span) AND specifying the full time span with a > standard time bounds? Would that provide sufficient information? > > Grace and peace, > > Jim > > On 2/15/16 7:02 AM, Hollis, Dan wrote: > >Hi Karl, > > > >This is a real use case for us too. And not just for short climatologies. > >When we compute our 30-year normals we use only the data from those 30 > >calendar years e.g. for 1981-2010 normals we use data from Jan 1981 to Dec > >2010. Like you we create monthly normals first and then combine these to > >create seasonal normals. I'd not come up with a way to describe the result > >in a CF-compliant way so I was interested to see your question. > > > >Using daily maximum temperature as an example, I guess what we are doing is > >something like this: > > > >time: maximum within days time: mean over days time: mean over years > >time: mean over months > > > >where 'mean over days' means over the days within each calendar month > >and 'mean over months' means over the months within a season > > > >I cannot immediately see how to extend/adapt the convention to allow for > >this possibility. > > > >Regards, > > > >Dan > > > > > > > > > > > >-----Original Message----- > >From: CF-metadata [mailto:[email protected]] On Behalf Of > >Karl Taylor > >Sent: 11 February 2016 20:50 > >To: [email protected] > >Subject: Re: [CF-metadata] How to build CF-compliant seasonal climatology > >when data begins within a season > > > >Hi Jonathan, > > > >Our thinking is the same on this. Thanks. > > > >By the way it is a real use case and I think it is scientifically > >defensible: I have 11 full years of data and I first compute a > >climatological annual cycle, yielding 12 climatological months. Then I > >compute the climatology for each of the seasons from the monthly > >climatology. This allows me to use all the data in the 11 years. I > >especially would want to do it this way if I only had 2 or 3 years of data > >because I wouldn't want to omit any of it. > > > >[Of course you wouldn't be able to do this if you were calculating say a > >trend of individual seasons; in that case you clearly wouldn't want to > >consider partial seasons.] > > > >best wishes, > >Karl > > > >On 2/11/16 12:20 PM, Jonathan Gregory wrote: > >>Dear Karl > >> > >>I agree with Seth that this isn't anticipated by the design of the > >>convention, which assumes that the mean over seasons is composed of a > >>number of complete seasons. Is this a real use-case, with a DJF mean > >>made by including JF from one NH winter and D from another? It seems a > >>bit odd to me. I wouldn't compute a monthly mean of anything if 2/3 of > >>the days were missing in the month. But, following this logic, your > >>original choice of "1999-12-1" to "2011-3-1" is OK, and it "just > >>happens" that Dec 1999 and Jan-Feb 2011 are actually not included, as > >>if they were missing data. Their omission is not recorded by the > >>climatology bounds but, equally, if Dec 2005 or Jan-Feb 2008 (for > >>example) were missing when computing the mean you would not know about it > >>from the climatology bounds. So perhaps it doesn't matter. > >> > >>To spell out exactly which months were used, it would be necessary to > >>record also the time coordinate and bounds before the collapse. In > >>various tickets we have discussed but not agreed a convention for doing > >>that, as extra info. > >>Alternatively you could record it as unstandardised info as a comment > >>in () in the cell_methods, as you note. > >> > >>Best wishes > >> > >>Jonathan > >> > >>----- Forwarded message from Karl Taylor <[email protected]> ----- > >> > >>>Date: Wed, 10 Feb 2016 15:37:01 -0800 > >>>From: Karl Taylor <[email protected]> > >>>To: [email protected] > >>>Subject: [CF-metadata] How to build CF-compliant seasonal climatology when > >>> data begins within a season > >>>User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:38.0) > >>> Gecko/20100101 Thunderbird/38.5.1 > >>> > >>>Dear CF community, > >>> > >>>In representing the seasonal climatology based on data available for > >>>the period January 1, 2000 through December 31 2010, what would be > >>>the correct climatology_bounds? > >>> > >>>climatology_bounds = "1999-12-1", "2011-3-1", > >>> "2000-3-1", "2010-6-1", > >>> "2000-6-1", "2010-9-1", > >>> "2000-9-1", "2010-12-1" ???? > >>> > >>>I would note that this seems to capture the idea that we are > >>>reporting seasonal means, but it also seems to indicate that this is > >>>based in part on data from Dec. 1999 and Jan.-Feb. 2011, when it > >>>isn't. Is this the best I can do? [Of course the convention can > >>>never tell us if data are complete in forming a climatology. If 1 > >>>year were missing, this would not affect the attributes.] > >>> > >>>I suppose the in the cell_methods attribute ("time: mean over days > >>>time: mean over years" I could add non-standardized information (as > >>>permitted by CF), for example: "time: mean over days time: mean > >>>over years (with data from the period 2000-1-1 to 2011-1-1)" > >>> > >>>thanks for any suggestions, > >>>Karl > >>> > >>> > >>> > >>>_______________________________________________ > >>>CF-metadata mailing list > >>>[email protected] > >>>http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > >>----- End forwarded message ----- > >>_______________________________________________ > >>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 > >_______________________________________________ > >CF-metadata mailing list > >[email protected] > >http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > -- > CICS-NC <http://www.cicsnc.org/> Visit us on > Facebook <http://www.facebook.com/cicsnc> *Jim Biard* > *Research Scholar* > Cooperative Institute for Climate and Satellites NC <http://cicsnc.org/> > North Carolina State University <http://ncsu.edu/> > NOAA National Centers for Environmental Information <http://ncdc.noaa.gov/> > /formerly NOAA’s National Climatic Data Center/ > 151 Patton Ave, Asheville, NC 28801 > e: [email protected] <mailto:[email protected]> > o: +1 828 271 4900 > > /Connect with us on Facebook for climate > <https://www.facebook.com/NOAANCEIclimate> and ocean and geophysics > <https://www.facebook.com/NOAANCEIoceangeo> information, and follow > us on Twitter at @NOAANCEIclimate > <https://twitter.com/NOAANCEIclimate> and @NOAANCEIocngeo > <https://twitter.com/NOAANCEIocngeo>. / > > > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
