Custom Query (125 matches)

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';
......
values::
   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

.....

and

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).

In example 7.3 ("Cell areas for a spherical geodesic grid") the standard_name for the area of the grid cell is given as "area", which is not in the current standard_name table. The correct standard_name for this variable is "cell_area", so a correction of this defect should be made.

1. Title

Add absolute value statistics to cell methods

2. Moderator

David Hassell

3. Requirement

The statistics mabs/mibs/mebs stand for "Maximum absolute value", "Minimum absolute value", and "Mean absolute value", respectively. They are similar to max/min/mean statistics, and they can be useful in characterizing data when one wants positive-definite metrics. mebs (unlike mean) does not allow positive and negative values to compensate eachother. Unlike rms, mebs not does weight outliers quadratically. NCO implements mabs/mibs/mebs as fundamental statistics (like max/min/mean), and annotates the cell_methods attribute of variables reduced by these statistics with the strings "maximum_absolute_value", "minimum_absolute_value", "mean_absolute_value".

4. Initial Statement of Technical Proposal

This recommendation could be implemented in CF by inserting the following lines into Table E.1. Cell Methods

​http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/build/cf-conventions.html#appendix-cell-methods

cell_methods:		Units:	Description:
maximum_absolute_value	u	Maximum absolute value
minimum_absolute_value	u	Minimum absolute value
mean_absolute_value	u	Mean absolute value

5. Benefits

This would improve the CF-compliance of fields processed by absolute-value statistics.

6. Status Quo

There is no standard CF terminology to describe absolute-value statistics so fields analyzed with these methods may have missing, erroneous, or non-standard cell_methods for this stage of processing. Unless the statistics were computed with NCO which has implemented the proposed cell_methods since February, 2015.