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#11 duplicate A standard for CF variable names ("short names") should be added. cf-conventions@… balaji

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.

#150 duplicate Clarification of use of standard region names in "region" variables. cf-conventions@… martin.juckes

The CF standard name region has the current description "A variable with the standard name of region contains strings which indicate geographical regions. These strings must be chosen from the standard region list." This description implies that the variable should be of character type, but it is often more convenient to have an integer variable and make a clear link to the region names using flag_values and flag_meanings. The proposal is to clarify the definition so that either usage is acceptable and include an example of the latter usage in the convention text. It is also proposed that an appendix be added to the CF Convention text to state clearly any constraints on file meta-data which are implied by the CF Standard Name definitions, so that it is possible to test such constraints in the CF checker.

New description for CF standard name "region"

A variable with the standard name of region must have values associated with geographical regions from the CF standard region list, either as a character variable using the region names directly or as an integer variable with values linked to region names through flag_values and flag_meanings attributes.

New usage example in CF Convention text

The following should be placed at the end of 6.1.1, after example 6.2

A variable with standard name 'region' may also be of integer type and use 'flag_values' and 'flag_meanings' attributes to express the relationship between the integers and the region names:

integer basin(basin);
       standard_name: region;
       flag_values: '1 2 3';
       flag_meanings:'atlantic_arctic_ocean indo_pacific_ocean global_ocean';
   basin: 1, 2, 3;

New Appendix Section

Change "Appendix B: Standard Name Table Format" to:

Appendix B: Standard Names

B.1: Standard Name Table Format



B.2 Constraints for specific standard names

B.2.1: region

Variables with standard name region must be one of:

  • type character, with values taken from the CF standard region list;
  • type integer, with flag_values and flag_meanings attributes. The flag_meanings attributes must be a space separatd list of values from the CF standard region list (see example 6.2).
#4 wontfix Archive cf-metadata mailing list halliday1 halliday1
  • Copy cf-metadata archives to Plone website
  • Create cf-metadata@…
  • If someone emails the old list, send them a pointer to the new list for a period of time
  • After some amount of time, decomission the old list
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