Mark, I'm looking at this from the standpoint of the use of an ancillary variable to provide "metadata about the individual values of another data variable". The way I think of it, the atmosphere profile used to produce a given <energy deposited> value falls under the category of metadata for the <energy deposited> value. I don't see any need to restrict this metadata to be a scalar value per primary variable value. So, in my example, there is a model atmosphere density profile that can be associated with each value of the <energy deposited> variable. I feel that the profile provides information about the <energy deposited> value. In fact, we already do this sort of thing with bounds variables, which to my mind are specializations of ancillary variables.
If there is no driving reason to restrict the definition of ancillary variables, I'd encourage folks to leave it as is. I think that with proper attention to use of names and coordinates, an ancillary variable that has multiple values for each primary variable can be made easily understandable. Grace and peace, Jim Jim Biard Research Scholar Cooperative Institute for Climate and Satellites Remote Sensing and Applications Division National Climatic Data Center 151 Patton Ave, Asheville, NC 28801-5001 [email protected] 828-271-4900 On Mar 15, 2013, at 7:37 AM, "Hedley, Mark" <[email protected]> wrote: > Hello Jim > > you present an interesting case, thank you > > I can see how I can relate > <energy deposited>(x,y,z,t) > to an ancillary variable of > <model atmosphere density profile>(x,y,z) > > In this case, for any value in my <energy deposited> data array I can > retrieve an appropriate value for my ancillary variable, <model atmosphere > density profile>. > > I am assuming that I can aggregate (integrate?) my <energy deposited> data > over z,to result in the total energy deposited as a function of x, y and t. > > The atmosphere density profile was an input to this calculation, I believe. > > If i try to store this as an ancillary variable for my result I am no longer > able to reference an appropriate value in the <model atmosphere density > profile> data array for a given value in the <energy deposited>. > > The conventions state > 'The nature of the relationship between variables associated via > ancillary_variables must be determined by other attributes.' > (http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch03s04.html) > > I am worried that in this case I can no longer understand this association. > The ancillary variable is defined with respect to a different domain from the > data variable. > > I might happily choose to ship two data variables in the same file, but do I > really mean that the <model atmosphere density profile> is an intrinsic part > of my <energy deposited> dataset? > > what do you think? > > mark > > > From: CF-metadata [[email protected]] on behalf of Jim Biard > [[email protected]] > Sent: 14 March 2013 13:51 > To: [email protected] > Subject: Re: [CF-metadata] Ancillary Data > > Mark, > > I've been following this thread silently, but your statement in your last > posting has prompted me to speak up. I can easily imagine a situation in > which I might desire to have one variable reference another variable in which > not all dimensions are shared. As an example, let's say that I have a > variable a[X,Y,T], which contains the total energy deposited per day into the > atmosphere by charged particles (from the solar wind & Van Allen belts) on a > lon/lat grid as a function of time. (Something I used to work on many years > ago.) Let's then say that I have another variable, b[X,Y,Z], which > represents the model atmosphere density profile on the same lon/lat grid as a > function of altitude. This density profile was used in the calculation of > the energy deposition values stored in variable a. Variable b is clearly > valid as an ancillary variable for a, isn't it? > > Grace and peace, > > Jim > > Jim Biard > Research Scholar > Cooperative Institute for Climate and Satellites > Remote Sensing and Applications Division > National Climatic Data Center > 151 Patton Ave, Asheville, NC 28801-5001 > > [email protected] > 828-271-4900 > > On Mar 14, 2013, at 7:53 AM, "Hedley, Mark" <[email protected]> > wrote: > >> Thank you for the responses on this topic. >> >> So far I have not found an example of ancillary variable use where >> >> the ancillary variable references file dimensions which are not referenced >> by the data variable with the referencing ancillary_variables attribute. >> >> I do not think this should be valid, as it is not practical to relate the >> ancillary variable data to the data variable. However, I do not think the >> Conventions are clear enough in banning this. >> >> I have raised a trac ticket: >> https://cf-pcmdi.llnl.gov/trac/ticket/98, >> which requires a moderator; please may someone volunteer to moderate this >> ticket? >> >> thank you >> mark >> >> ________________________________________ >> From: CF-metadata [[email protected]] on behalf of Hedley, >> Mark [[email protected]] >> Sent: 18 February 2013 10:45 >> To: andrew walsh >> Cc: [email protected] >> Subject: Re: [CF-metadata] Ancillary Data >> >> Hello Andrew >> >> thank you for the response, my reading of your cases is that they are all >> 'a' or 'b' in the terms I stated. >> >> There are no ancillary variables which reference a dimension of the netCDF >> file not referenced by the data variable with the ancillary_variables >> attribute. >> >> I think these are types of case I am particularly concerned to find examples >> of, or, preferably, discount explicitly. >> >> much obliged >> mark >> >>> On 2/13/13 12:15 PM, Hedley, Mark wrote: >>>> a. reference the same file dimensions as the data variable with the >>>> ancillary_variables attribute references >>>> >>>> b. reference a subset of the file dimensions referenced by the data >>>> variable with the ancillary_variables attribute >>>> >>>> c. reference file dimensions which are not referenced by the data >>>> variable >>>> with the ancillary_variables attribute >> >> -----Original Message----- >> From: andrew walsh [mailto:[email protected]] >> Sent: Fri 2/15/2013 3:20 AM >> To: Hedley, Mark >> Cc: [email protected]; [email protected] >> Subject: Re: [CF-metadata] Ancillary Data >> >> Hi Mark, >> >> We are using the ancilliary_variables attribute in a real world case for CTD >> profile data >> (1 netCDF per CTD profile). Not sure if our use case fits with with your >> examples a,b,c but here is a abbreviated CDL version:- >> >> dimensions: >> >> pressure = UNLIMITED ; // (9 currently) >> >> variables: >> double time ; >> time:standard_name = "time" ; >> .... >> byte time_qc_flag; >> time_qc_flag:long_name = "quality control flag for time (Level 1 flag)" ; >> .... >> >> double latitude ; >> latitude:standard_name = "latitude" ; >> ... >> >> double longitude ; >> longitude:standard_name = "longitude" ; >> ... >> >> byte position_qc_flag; >> position_qc_flag:long_name = "quality control flag for position (Level 1 >> flag)" ; >> .... >> >> double pressure(pressure) ; >> pressure:standard_name = "sea_water_pressure" ; >> ... >> >> double temperature(pressure) ; >> temperature:_FillValue = -99.99 ; >> temperature:standard_name = "sea_water_temperature" ; >> temperature:units = "degrees_C" ; >> temperature:valid_min = -2 ; >> temperature:valid_max = 40 ; >> temperature:ancillary_variables = "temperature_whole_profile_flag >> temperature_qc_flag temperature_sd_test" ; >> temperature:coordinates = "time latitude longitude pressure" ; >> >> byte temperature_whole_profile_flag ; >> temperature_whole_profile_flag:long_name = "qc flag for whole temperature >> profile (primary L1 flag)" ; >> temperature_whole_profile_flag:quality_control_convention = "Proposed IODE >> qc >> scheme March 2012" ; >> temperature_whole_profile_flag:valid_min = 1 ; >> temperature_whole_profile_flag:valid_max = 9 ; >> temperature_whole_profile_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; >> temperature_whole_profile_flag:flag_meanings = "good >> not_evaluated_or_unknown >> suspect bad missing" ; >> >> byte temperature_qc_flag(pressure) ; >> temperature_qc_flag:long_name = "quality control flag for temperature >> (primary >> Level 1 flag)" ; >> temperature_qc_flag:standard_name = "sea_water_temperature status_flag" ; >> temperature_qc_flag:quality_control_convention = "Proposed IODE qc scheme >> March 2012" ; >> temperature_qc_flag:valid_min = 1 ; >> temperature_qc_flag:valid_max = 9 ; >> temperature_qc_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; >> temperature_qc_flag:flag_meanings = "good not_evaluated_or_unknown suspect >> bad >> missing" ; >> temperature_qc_flag:coordinates = "time latitude longitude pressure" ; >> >> byte temperature_sd_test(pressure) ; >> temperature_sd_test:long_name = "qc flag for monthly temperature standard >> deviation test (secondary L2 flag)" >> temperature_sd_test:quality_control_convention = "Proposed IODE qc scheme >> March 2012" ; >> temperature_sd_test:valid_min = 0 ; >> temperature_sd_test:valid_max = 2 ; >> temperature_sd_test:flag_values = 0b, 1b, 2b ; >> temperature_sd_test:flag_meanings = "passed failed unknown" ; >> temperature_sd_test:coordinates = "time latitude longitude pressure" ; >> >> double salinity(pressure) ; >> salinity:_FillValue = -99.99 ; >> salinity:standard_name = "sea_water_practical_salinity" ; >> salinity:units = "psu" ; >> salinity:valid_min = 0 ; >> salinity:valid_max = 45 ; >> salinity:ancillary_variables = "salinity_whole_profile_flag salinity_qc_flag >> salinity_sd_test" >> salinity:coordinates = "time latitude longitude pressure" ; >> >> byte salinity_whole_profile_flag ; >> salinity_whole_profile_flag:long_name = "qc flag for whole salinity profile >> (primary L1 flag)" ; >> salinity_whole_profile_flag:quality_control_convention = "Proposed IODE qc >> scheme March 2012" ; >> salinity_whole_profile_flag:valid_min = 1 ; >> salinity_whole_profile_flag:valid_max = 9 ; >> salinity_whole_profile_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; >> salinity_whole_profile_flag:flag_meanings = "good not_evaluated_or_unknown >> suspect bad missing" ; >> >> byte salinity_qc_flag(pressure) ; >> salinity_qc_flag:long_name = "quality control flag for salinity (primary >> Level >> 1 flag)" ; >> salinity_qc_flag:standard_name = "sea_water_practical_salinity status_flag" >> ; >> salinity_qc_flag:quality_control_convention = "Proposed IODE qc scheme March >> 2012" ; >> salinity_qc_flag:valid_min = 1 ; >> salinity_qc_flag:valid_max = 9 ; >> salinity_qc_flag:flag_values = 1b, 2b, 3b, 4b, 9b ; >> salinity_qc_flag:flag_meanings = "good not_evaluated_or_unknown suspect bad >> missing" ; >> salinity_qc_flag:coordinates = "time latitude longitude pressure" ; >> >> byte salinity_sd_test(pressure) ; >> salinity_sd_test:long_name = "qc flag for monthly salinity standard >> deviation >> test (secondary L2 flag)" >> salinity_sd_test:quality_control_convention = "Proposed IODE qc scheme March >> 2012" ; >> salinity_sd_test:valid_min = 0 ; >> salinity_sd_test:valid_max = 2 ; >> salinity_sd_test:flag_values = 0b, 1b, 2b ; >> salinity_sd_test:flag_meanings = "passed failed unknown" ; >> salinity_sd_test:coordinates = "time latitude longitude pressure" ; >> >> int profile ; //Unique integer to identify each profile >> profile:long_name = "profile identifier" >> .... >> >> Andrew Walsh >> >> ----- Original Message ----- >> From: "Hedley, Mark" <[email protected]> >> To: <[email protected]>; <[email protected]> >> Sent: Thursday, February 14, 2013 10:40 PM >> Subject: Re: [CF-metadata] Ancillary Data >> >> >>> Hi Nan >>> >>> I think I understand you approach, it seems logical and helpful to me. >>> >>> It feels like all your examples are in my category b: >>> >>>> b. reference a subset of the file dimensions referenced by the data >>>> variable >>>> with the ancillary_variables attribute >>> >>> and thus relate to the data variable in the same way auxiliary_coordinates >>> do, >>> just with different inferred semantics. >>> >>> many thanks for the feedback >>> >>> mark >>> >>> -----Original Message----- >>> From: CF-metadata on behalf of Nan Galbraith >>> Sent: Wed 13/02/2013 19:55 >>> To: [email protected] >>> Subject: Re: [CF-metadata] Ancillary Data >>> >>> I use a singleton variable to record the magnetic correction that's been >>> applied to my wind and/or current variables; it's dim(1) and is listed as >>> an ancillary to any variables that have been affected by the rotation. >>> >>> It could be an attribute of each of those variables, but making it a >>> free-standing >>> variable lets me give it units and attributes. That's important because I >>> record the model name and version date, the URL of the NGDC calculator >>> site, >>> the inputs to the model (date and location for which the calculation was >>> done) >>> and the estimated rate of change. >>> >>> Maybe this is just a technicality - but I also use an empty 'container' >>> variable for >>> instruments, which has ancillary variables with a depth dimension for >>> manufacturer, >>> model, serial number, and reference URL. The instrument variable is >>> tied to 'obs data' >>> variables via NODC's 'instrument' attribute, but has no dimensions of >>> its own; the >>> individual component variables (like serial number) have a dimension >>> that matches >>> the depth dimension of the obs data variables. >>> >>> - Nan >>> >>> On 2/13/13 12:15 PM, Hedley, Mark wrote: >>>> Hello CF community >>>> >>>> I have been perusing the CF conventions again, particularly the section on >>>> Ancillary Data >>>> http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/ch03s04.html >>>> >>>> The conventions make the statement: >>>> >>>> The nature of the relationship between variables associated via >>>> ancillary_variables must be determined by other attributes. >>>> >>>> The example given provides data variables which reference the same >>>> dimensions >>>> in the file: thus they data arrays are the same size. However, the >>>> conventions do not seem to mandate this. >>>> >>>> I am interested in the use of the >>>> ancillary_variables >>>> attribute in real world datasets. >>>> >>>> Do people have examples they can share of ancillary datasets which: >>>> >>>> a. reference the same file dimensions as the data variable with the >>>> ancillary_variables attribute references >>>> >>>> b. reference a subset of the file dimensions referenced by the data >>>> variable with the ancillary_variables attribute >>>> >>>> c. reference file dimensions which are not referenced by the data >>>> variable >>>> with the ancillary_variables attribute >>>> >>>> I am particularly interested in examples of case c, as I feel this is >>>> markedly different from cases a and b and requires a different kind of >>>> support if it is in use. >>>> >>>> many thanks >>>> mark >>>> _______________________________________________ >>>> CF-metadata mailing list >>>> [email protected] >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>>> >>> >>> >>> -- >>> ******************************************************* >>> * Nan Galbraith Information Systems Specialist * >>> * Upper Ocean Processes Group Mail Stop 29 * >>> * Woods Hole Oceanographic Institution * >>> * Woods Hole, MA 02543 (508) 289-2444 * >>> ******************************************************* >>> >>> >>> _______________________________________________ >>> 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 >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
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