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Ticket Resolution Summary Owner Reporter
#28 wontfix Correct recommended units for lat and lon cf-conventions@… apamment

Beate Geyer has pointed out that the recommended units for latitude and longitude coordinate variables in sections 4.1 and 4.2 of the conventions document are inconsistent with the canonical units published in the standard name table.

Sections 4.1 and 4.2 of the conventions recommend degrees_north and degrees_east for lat and lon, respectively. The standard name table uses the singular form for the canonical units, i.e. degree_north and degree_east. The two sources of documentation should be made consistent. Beate has indicated a preference for the singular form of the unit, therefore it is proposed that the conventions document should be modified to agree with the standard name table. This requires modification to the sentences in sections 4.1 and 4.2 beginning with "The recommended unit ...".


#61 fixed 2 new cell methods cf-conventions@… awalsh

1. Title

2 new cell methods

2. Moderator

Moderator - Alison Pammet Proposer - Andrew Walsh. Contributors and discussion - Jonathon Gregory, Roy Lowry, Mark Kulmar

3. Requirement

Extend the cell methods table with 2 new cell methods.

4. Initial Statement of Technical Proposal

As a result of discussion around the adding 9 new sea surface wave data

parameters to the CF standard names list it was decided to reduce this proposal to 6 new standard names thereby reducing the proliferation of new names. This reduction was achieved by introducing a 'common concept' name called 'sea_surface_wave_height' qualified by one of 4 cell methods i.e.

mean maximum root_mean_square mean_of_upper_decile

which will describe 4 of the statistical wave height variables:

sea_surface_mean_wave_height sea_surface_maximum_wave_height sea_surface_root_mean_square_wave_height sea_surface_wave_mean_of_highest_one_tenth_waves


'mean' and 'maximum' are existing cell methods. 'root_mean_square' and 'mean_of_upper_decile' are the 2 new cell methods proposed.

The other 5 new standard names proposed were:

sea_surface_wave_mean_crest_period sea_surface_wave_significant_wave_period sea_surface_wave_period_at_second_largest_peak_of_variance_spectral_density sea_surface_wave_variance_spectral_density_zeroth_frequency_moment sea_surface_wave_root_mean_square_amplitude_from_variance_spectral_density

5. Benefits

This proposal would benefit the netCDF user community as it reduces the proliferation of new names by using a common concept standard name qualified by cell methods. These 2 new cell methods may also find useful application with

other data parameters wherever statistical methods of 'root_mean_square' or 'mean_of_upper_decile' were applied.

6. Status Quo

Status quo would be to use non-standard long_names for these sea surface wave data variables with the disadvantage of poor interoperability.

#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.

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