Re: [CF-metadata] interplay of standard name modifiers, cell_methods -- is there a problem?
Hi Jim, There are a lot of nails being hit on the head at the moment. The Standard Name attribute was conceived as a standardised label for the geophysical phenomenon - a sort of grouping term for what was being measured. Note that the Standard Name isn't a mandatory attribute in CF - the rules state that there either needs to be a long name OR a Standard Name! Over time there have been various attempts to turn the Standard Name into something different - the 'single location to gather important information about the kind of data contained in a variable' as you put it (I like that description). For example, the OceanSites community made the Standard Name mandatory in their CF profile. This caused requests to be made for new Standard Names appropriate to your definition, but not the original Standard Name concept. Some of these got through: others didn't, which makes the entity definition of the Standard Name concept a little blurred. Another strategy has been to provide a 'signpost' pointing out the location of all the various bits of information needed to fulfil your definition. There was a proposal called Common Concept (Trac ticket 24) designed to do this. Unfortunately, it required a small but significant amount of effort to set up that was never resourced. In fact, it seemed like it was cursed - I even had to hand back funding allocated for the purpose because a critical staff member left at a time when there was a total ban on UK public service recruitment. A 'resource light' version of this strategy - CF String Syntax (Trac ticket 94 which I'm moderating) - is currently ready to implement once it has been written up as a Conventions document update. If we get this finished do you think it would resolve the problems you see? Cheers, Roy. Because it isn't mandatory in CFPlease note that I now work part-time from Tuesday to Thursday. E-mail response on other days is possible but not guaranteed! From: CF-metadata [mailto:cf-metadata-boun...@cgd.ucar.edu] On Behalf Of Jim Biard Sent: 02 April 2013 21:19 To: cf-metadata@cgd.ucar.edu Cc: Jonathan Gregory Subject: Re: [CF-metadata] interplay of standard name modifiers, cell_methods -- is there a problem? Jonathan, You haven't been unclear about how we got into the state we are currently in. We got to now by adding bits here and there as needs arose without always thinking about the implications for the whole system down the road (which you did a great job of describing). A lot of good work has been done to get where we are today, and I appreciate that. I also think that there is room for improvement in how we represent values that result from operations applied to measurements. Yes, we could add paragraphs to the documentation to tell users to go look in various places when they are trying to figure out what the contents of a variable are, but that is not user-friendly behavior. I want to make it easy and intuitive to understand what sort of information a variable contains. If we consider the standard name attribute as the location where the essence of the variable contents is described using a controlled vocabulary, it makes sense to provide a mechanism within that vocabulary for distinguishing between a direct measurement (air temperature) and information about a measurement (standard deviation of air temperature). We provide this for some operations on measurements (number of observations, standard error, etc), but not for others (standard deviation, variance, anomaly, etc). Expanding the list of standard name modifiers in the CF Metadata Conventions would allow us to make variables more self-describing and less confusing, and allow a user (or software) to look in a single location to gather important information about the kind of data contained in a variable (which I see as the purpose of the standard_name attribute). 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 jim.bi...@noaa.govmailto:jim.bi...@noaa.gov 828-271-4900 On Apr 2, 2013, at 1:05 PM, Jonathan Gregory j.m.greg...@reading.ac.ukmailto:j.m.greg...@reading.ac.uk wrote: Dear all Jim asked, As some examples of the confusing situation we have now, why do we have a separate word modifier number_of_observations instead of a number_of_observations_of_X transformation modifier? Why don't we have variance_of_X or anomaly_of_X transformations (or separate word modifiers variance or anomaly)? Why isn't there a cell method for standard error? I can't discern any logic behind the current partitioning. I've tried to explain how this came about, but perhaps I am not being clear, so let me try again: * We introduced the modifiers like number_of_observations for those situations where it was thought likely that a large number of standard names would need them.
[CF-metadata] Anyone manning the Trac desk?
Hi. I sent an email to webmas...@pcmdi.llnl.gov requesting to be registered with the Trac system, but have received no reply. Is there someone out there who can help me? 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 jim.bi...@noaa.gov 828-271-4900 ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
[CF-metadata] Consistent standard_names for satellite derived radiance quantities
Folks: In the past few months there have been three standard_names proposed related to radiance or irradiance quantities at the top of the atmosphere derived from data sensed by a satellite. The proposals are as follows: (a) Message subject: cf-satellite Digest, Vol 29, Issue 1 from Peter Miu standard_name: toa_spectral_irradiance with canonical units mW m-2 (cm-1)-1 Definition: Irradiance which is relevant for any sensor measuring in the UV-VIS and NIR. This parameter is reported by integrating over the whole sphere. (b) Message subject: cf-satellite Digest, Vol 29, Issue 1 from Peter Miu standard_name: toa_outgoing_inband_radiance with canonical units mW m-2 sr-1 Definition: outgoing means emitted toward outer space; the radiance is integrated over a discrete band. (c) Message subject: [CF-metadata] New Standard Names for Satellite Data from Aleksandar Jelenak Standard_name: toa_outgoing_spectral_radiance with canonical units mW m-2 sr-1 (cm-1)-1 Definition: toa means top of atmosphere; outgoing means emitted toward outer space spectral means per unit wavenumber or as a function of wavenumber. Radiance is the radiant power per unit area in a particular direction per unit of solid angle. The prefixes toa and outgoing identified in the CF standard name guidelines are applicable. The overarching consistency issue of the quantities revolves around their units. For both radiance and irradiance, there are four types of potentially reported quantities where the mappings between them is not trivial, and, more specifically, not supported with a CF standard name modifier or cell_method. The types of quantities are as follows with a focus only on the contrasting characteristics (in a given direction per unit area per unit solid angle are omitted): 1)Power integrated over all wavelengths. 2)Power at a discrete monochromatic wavelength. 3)Power integrated over a discrete bandpass. 4)Power per unit wavelength integrated over a discrete bandpass and normalized by the bandpass response function (i.e. the spectral response of the sensor). Given . * The four types of radiance irradiance quantities identified immediately above. * The need to conform with existing applicable CF standard name conventions, specifically the prefixes toa and outgoing. * The fact that 2) 4) immediately above are spectral quantities. * The need to capture the frequency band associated with the radiance/irradiance quantity for 3) 4) immediately above. . results in the following standard_names, and strawman definitions and canonical units for the four radiance quantities. Note that we have leveraged the work done by Peter and Aleksander. ++ #1 standard_name: toa_outgoing_radiance Definition: toa means top of atmosphere. outgoing means emitted toward outer space. This quantity is the radiant power per unit area in a given direction per unit solid angle integrated over all wavelengths. Canonical units: W m-2 sr-1 ++ #2 standard_name: toa_outgoing_spectral_radiance Definition: toa means top of atmosphere. outgoing means emitted toward outer space. spectral means per unit wavenumber or as a function of wavenumber. Radiant power per unit area in a given direction per unit solid angle at a discrete monochromatic wavelength. Canonical units: mW m-2 sr-1 (cm-1)-1 Note: A coordinate variable to capture the wavelength may be used. ***This quantity and its standard_name are identical to that proposed by Aleksander. See c) above. *** + #3 standard_name: toa_outgoing_inband_radiance Definition: toa means top of atmosphere. outgoing means emitted toward outer space. inband means the radiance quantity is for a discrete bandpass. This quantity is the radiant power per unit area in a given direction per unit solid angle integrated over a discrete bandpass. Canonical units: W m-2 sr-1 Note: A coordinate variable to capture the center wavelength, and potentially, a boundary variable to capture the bandpass extents may be used. ***This quantity and its standard_name are identical to that proposed by Peter. See b) above. *** + #4 standard_name: toa_outgoing_inband_spectral_radiance Definition: toa means top of atmosphere. outgoing means emitted toward outer space. inband means the radiance quantity is for a discrete bandpass. spectral means per unit wavenumber or as a function of wavenumber. This quantity is the radiant power per unit area in a given direction per unit solid angle per unit wavelength integrated over a discrete bandpass and normalized by the bandpass response function. Canonical units: mW m-2 sr-1 (cm-1)-1 Note: A coordinate variable to capture the center wavelength, and potentially, a boundary variable to capture the bandpass extents may be used. + There are analogous standard_name for the irradiance values. They are not included in this email to keep the material in as
