Improve CF Conformance: 7.1 Cell Boundaries

[jamesdoyle21]

7.1 Cell Boundaries
Requirements:

• The type of the bounds attribute is a string whose value is a single variable name. The specified variable must exist in the file.

This is confirmed to exist in the check_cell_boundaries function.

• A boundary variable must have the same dimensions as its associated variable, plus have a trailing dimension (CDL order) for the maximum number of vertices in a cell.

• A boundary variable must be a numeric data type.

• If a boundary variable has units, standard_name, axis, positive, calendar, leap_month, leap_year or month_lengths attributes, they must agree with those of its associated variable.

• Starting with version 1.7, a boundary variable must have a formula_terms attribute when it contains bounds for a parametric vertical coordinate variable that has a formula_terms attribute. In this case the same terms and named variables must appear in both except for terms that depend on the vertical dimension. For such terms the variable name appearing in the boundary variable’s formula_terms attribute must differ from that found in the formula_terms attribute of the coordinate variable itself. The boundary variable of the formula_terms variable must have the same dimensions as the formula_terms variable, plus a trailing dimension (CDL order) for the maximum number of vertices in a cell, which must be the same as the trailing dimension of the boundary variable of the parametric vertical coordinate variable. If a named variable in the formula_terms attribute of the vertical coordinate variable depends on the vertical dimension and is a coordinate, scalar coordinate or auxiliary coordinate variable then its bounds attribute must be consistent with the equivalent term in formula_terms attribute of the boundary variable.

Recommendations:

• The points specified by a coordinate or auxiliary coordinate variable should lie within, or on the boundary, of the cells specified by the associated boundary variable.

• Boundary variables should not have the _FillValue, missing_value, units, standard_name, axis, positive, calendar, leap_month, leap_year or month_lengths attributes.