Data Request Variables - Change vegtype coordinate

[CMIP-Data-Request-coleads]

Themes:

• Land & Land-Ice

Description

The vegtype coordinate uses model-specific categories.
To improve the inter-comparability among models, it would be useful to introduce a set of general categories.
Since some "fraction" variables are already defined on some vegetation categories, the set of categories to use in vegtype can be derived from that list.
In particular, they could be:
Broadleaf Deciduous
Broadleaf Evergreen
Needleleaf Deciduous
Needleleaf Evergreen
grass
crop
shrub

[martinjuckes]

Before compiling the CMIP6 request I did a review of the land cover types reported in CMIP5 which might be of interest: Workbook.

I support this change, using names from the CF Area Type table. However, I realise that the four tree types are not yet distinguished in the area type table. These categories were present in the CMIP6 and used in coordinates typetreebd etc, but the CF metadata was incomplete in the sense that it only specified the area_type as tree rather than fully qualifying it as broadleaf and deciduous.

For CMIP7 we should aim to get the additional area types approved.

If this change goes ahead, existing variables for single land area types, such as Emon.treeFracBdlDcd, and variables masked by a single area types, such as nppGrass, nppTree, can be omitted.

[martinjuckes]

Need to move to CF Conventions.

[martinjuckes]

See cf-convention/vocabularies#227