Update to CMIP7 LULCC forcings

[wwieder]

It looks like a preliminary dataset for LULCC is available for CMIP7 (scroll down the table with links)

Specifically, is the v3.0 dataset any different that what we're already using from TRENDY?
This github page could be helpful for tracking changes / updates to the dataset.

If this dataset is different from TRENDY, we should migrate to the latest v3 data so we're testing the model with LULCC data that's hopefully consistent with the final CMIP7 data.

@lawrencepj1 can you have a look at this dataset to see if it's different that what we've already integrated into the 5.3 tag?

[samsrabin]

See also: This brief slide deck with some info from Louise Chini; there's also a recording of her talk here.

[wwieder]

And this note from @ckoven on the FATES side

[lawrencepj1]

Hi Everyone
Just for reference this is actually "CMIP6Plus" based on the CMIP Forcings meeting this morning. It is a test version that will be updated if needed to CMIP7 in 2025.

https://wcrp-cmip.org/wp-content/uploads/2024/10/2024-10-29_Forcings-drop-in_session.pdf

That said I am very happy to start going through the LUH3 data and getting CTSM53 raw PFT data generated from the new data.
Thanks
Peter

[olyson]

Since we now have dynamic urban capability, I wonder if we should include urban in this version. I'm not sure what was done with urban previously in CMIP6, maybe it was assigned to some other landunit?

[lawrencepj1]

Hi @olyson

Urban is transient in the LUH data and the values from LUH are explicitly put into the raw CLM5 and CTSM53 PFT data. Mksurfdata however does not use the raw PCT_URBAN data. There is a lot more information required for CTSM than provided by LUH so it would not be useful as a source for final surface or landuse timeseries data.

Cheers
Peter

[olyson]

Thanks @lawrencepj1 . I was thinking that a simple and reasonable thing to do would be to use the PCT_URBAN supplied by LUH and assign it to a single density type (medium density, as that is by far the most common) and then simply splice in the static-in-time urban properties, which don't depend on PCT_URBAN and just depend on density type and region, into those files. We would end up with raw files that have the same information in them as we do now.
If you have a sample raw CLM5/CTSM53 file, I could experiment with that.

[lawrencepj1]

Hi @olyson

Yes not a problem at all. You can find the latest TRENDY and LUH derived CTSM53 raw data at:

/glade/campaign/cesm/development/lmwg/landuse_source_data/CTSM53RawData

SSP5-8.5 has the largest urban expansion of the future scenarios. Here is 2015 vs 2100 values from these two raw files:

globalctsm53TRSSP585Deg025_240728/mksrf_landuse_ctsm53_TRSSP585_2015.c240728.nc
globalctsm53TRSSP585Deg025_240728/mksrf_landuse_ctsm53_TRSSP585_2100.c240728.nc

Peter

[olyson]

Thanks @lawrencepj1 !

[wwieder]

At the SE meeting we noted this is something we want to be able to test, but not prioritize into CTSM dev at this stage

[lawrencepj1]

Meeting with @slevis-lmwg @ekluzek @mvdebolskiy:

Issues for discussion on CMIP6+ land use processing.

1. LUH3 has Plantation Forests. Do we want to process these explicitly or include them as Secondary Forests
2. Pre 1850 potential vegetation assumptions. These need to be clarified to include natural disturbance so we don't over specify forests in a natural world.

[slevis-lmwg]

1. LUH3 has Plantation Forests. Do we want to process these explicitly or include them as Secondary Forests

My gut response (that I shared with Peter) is to treat them as Secondary Forests for now, since the mksurfdata tool and the model can handle that without code changes.

[wwieder]

I think @slevis-lmwg's suggestion on plantation forests makes sense (include them as secondary forests).

I don't really know what do think about the potential veg question. Is this something that would be helpful to discuss in a targeted meeting, or the CLM science time slot on a Thursday?

How critical is it that we figure out a plan for potential veg for ongoing coupled model testing?