CMIP7 Standard names: lake_area_fraction

[christian-stepanek]

Christian Stepanek

2024-09-12

For each term please try to give the following:

- Proposed term to appear in the vocabulary lake_area_fraction

- Description: This is similar to land_area_fraction etc. but shall describe the fraction of lake coverage on a grid cell. It appears that there is not yet a name for the fraction of a grid cell covered by lakes. This is relevant for, e.g., PMIP, where differences in lake cover must be quantified.

- Unit: Fraction

[github-actions]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[taylor13]

There is related (duplicate?) discussion in #65 . I think somewhere we've decided that the way to handle specific area type fractions in the future is through adding that area type to the area type table and then attaching a scalar dimension to the area fraction variable. It's standard name would simply be "area_fraction". Will try to fill in more details later.

[martinjuckes]

I agree with Karl, in CMIP6 we added many area fractions in this way (e.g. for bare soil, grass, C3 grass, C4 grass, broadleaf deciduous trees, etc).

We would need a new lake term in the area type table

[efisher008]

Dear all,

Thank you Christian @christian-stepanek for your proposal. As @taylor13 and @martinjuckes have responded, this would ideally be handled by a new lake term in the area type table as has been mentioned in the discussion in issue #65 and utilising the dimensionality of the area fraction variable to achieve this. Do you have further questions on this? It sounds as though @taylor13 is happy to give some further clarification around how this would work if so.

Best wishes,
Ellie

[japamment]

Dear Christian @christian-stepanek,

I agree with @taylor13 and @martinjuckes that the best way forward is to add lake as a new entry to the CF area type table. Your variable could then use the existing standard name area_fraction and you would need to add a scalar coordinate variable with the standard name of area_type whose value would be the string 'lake'.

Would you be okay with taking this approach?

Best wishes,
Alison

[christian-stepanek]

This sounds like a sensible approach @japamment @taylor13 @martinjuckes, thanks a lot. I have to see how the details are to be implemented into the CMIP7 airtable framework, but it sounds like this has been done before.

All the best
Christian