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Ticket Resolution Summary Owner Reporter
#11 duplicate A standard for CF variable names ("short names") should be added. cf-conventions@… balaji
Description

1. Title

A standard for CF variable names ("short names") should be added.

2. Moderator

  1. Balaji

3. Requirement

In any of the data formats associated with CF (e.g netCDF) the variable name is its most convenient handle. Most command-line and script-based data tools use this handle. The NCO utilities for manipulating netCDF data, visualization and analysis tools such as ferret or grads or Matlab, all use the variable name as a handle.

This name is not currently included in the standard, though some de facto standards exist. In the absence of a standard, users cannot write scripts or methods that are general enough to apply across datasets from many sources.

For instance, a typical user request from GFDL is to make our internal variables names match what PCMDI (via the CMOR program) required for IPCC AR4: this would enable users who have developed new scientific analyses on their own data to apply them instantly to any model in the IPCC archive.

The CF standard_name attribute does not satisfy this need. Shortcomings include:

  • the standard_name is too long to type.
  • the standard_name attribute along does not uniquely identify a single variable in a file (example: "high", "middle" and "low" cloud amount all have the standard name cloud_area_fraction_in_atmosphere_layer, and are disambiguated using other attributes (height limits of associated layer).

4. Initial Statement of Technical Proposal

We propose a list of "CF short names".

  • Names should be short (6 character max) and human-typable.
  • Names should uniquely identify a physical variable.
  • Proposals to the standard_name list should also list a recommended short name.
  • It is desirable that names be vaguely mnemonic: e.g "slp" for sea level pressure. But this should not be a reason to have long debates over the short name.
  • The "PCMDI short name" used by IPCC AR4 is a good starting point for climate variables. Perhaps someone can suggest an equally useful starting point for weather (e.g based on ERA-40 or NCEP reanalysis datasets).

5. Benefits

Benefits and use cases are coverd in some slides prepared for GO-ESSP are attached here, and also available from Balaji's home page.

6. Status Quo

Without changing the standard, we might get by with de facto standards such as the AR4 short names; but the benefit is limited as many of us participate in multiple international modleing campaigns. There is no guarantee that all such campaigns remain consistent in their use of short names.

#12 fixed Formula terms for ocean_sigma_coordinate are incorrect kyle rsignell
Description

The format for the "ocean_sigma_coordinate" formula_terms attribute should be

formula_terms = "sigma: var1 eta: var2 depth: var3"

I checked the CF-conventions 1.0 doc from 2004 and it's correct there, but even version 1.0 of the docbook

http://cf-pcmdi.llnl.gov/trac/browser/cf-conventions/trunk/docbooksrc/appendix-d.xml?rev=1

has it wrong, repeating instead the "ocean_s_coordinate" formula_terms.

#13 fixed Procedure for correcting errors in the CF documents cf-conventions@… jonathan
Description

Rich Signell has pointed out an error in the CF standard document by raising a trac ticket. I think we need rules for deciding to make corrections, or there's a danger they might not be implemented. I propose the following:

  1. These rules apply to the CF conventions document, the conformance document, the standard name table and its guidelines.
  1. Errors in these documents can be corrected under these rules if it is clear that the text as it stands isn't what was agreed, because of a typographical or some other error. These rules can't be followed for making substantive changes. Errors in the standard names can alternatively be pointed out on the CF email list, and implemented by the manager of CF standard names (Alison) as part of a regular update.
  1. If someone thinks there is an error in a document, they should open a Trac ticket of type "defect" to point it out and to state what should be done to the text in order to correct the error.
  1. The correction is held to have been agreed if three weeks pass without anyone disagreeing with it. After that period, the ticket should be closed by the manager of the CF conventions (Kyle) or the manager of CF standard names (Alison), who will make the change. No moderator is needed because there cannot be any substantive discussion under these rules.
  1. If anyone disagrees that the correction should be made, because they think the document does have the intended meaning, then a correction cannot be made by these rules, the ticket should be closed, and the change should be proposed as an enhancement instead, following the rules for making changes to the CF standard, if the proposer wants to pursue the issue.

It feels a bit bureaucratic to have rules, but I think it may be necessary because experience shows that without rules we find it hard to reach conclusions. Please post your comments to this ticket.

Jonathan

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