Mapping layer specific variables to cf name

[khintz]

It is unresolved how to map variables like, low, medium and high cloud cover (lcc, mcc and hcc) to cf-standard name.

discipline  parameterCategory   parameterNumber cf_standard_name                        cf_table_version
0           6                   3               cloud_area_fraction_in_atmosphere_layer 86
0           6                   4               cloud_area_fraction_in_atmosphere_layer 86
0           6                   5               cloud_area_fraction_in_atmosphere_layer 86

lcc, mcc and hcc are all mapped to the same cf_standard_name as cloud_area_fraction_in_atmosphere_layer.

The CF standard is quite clear on how to define the different layers (https://cfconventions.org/Data/cf-standard-names/current/build/cf-standard-name-table.html):

There must be a vertical coordinate variable indicating the extent of the layer(s). If the layers are model layers, the vertical coordinate can be model_level_number, but it is recommended to specify a physical coordinate (in a scalar or auxiliary coordinate variable) as well.

The extent of each variable can probably be figured out, but it is unclear how we would like to map this information in the table, if we do want to provide that information at all.