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How to use fluxes from land in a coupled simulation?

wvsi3w

wvsi3w
Member
Hello everyone.
I have a general question about the possibility of running the fully coupled CESM (or at least CAM-CLM):

From my understanding of running CLM, the land is forced by the atmosphere. Is there a version of the CESM simulation that the atmosphere is driven by fluxes coming from land? Do you know of any type of CAM-CLM coupled simulations in which the atmosphere is forced by the fluxes that come from the land?

I checked the inputdata directory of a fully coupled simulation, and I see the same lnd initial data (ndep, maps, surfdat, ...) that I saw in land-only simulations. When you do a land-only simulation, the Carbon or Methane state of land changes (e.g., thawing of permafrost results in CH4, VegC, CO2, etc, to change). These fluxes that are coming from land, like Methane and Carbon, etc., will be going into the ecosystem (atmosphere as well), so how can we use these outputs (fluxes) as an initial file or forcing for the atmosphere?


The only option that comes to my mind is to use a restart file from the condition of a land-only simulation as an initial file (finidat) for the land namelist, and do a CAM-CLM coupled simulation to see the interaction of the atmosphere with land as a result of using that initial condition (restart file from land). This way, we are just studying the feedback of CAM-CLM.

But, if you want to study the impacts of already thawed permafrost in a certain year on the atmosphere, then I dont see much option in a coupled simulation.
The reason I am asking this is our duration of study is long (~1500 years of land simulation), and at the end we will have the final condition of permafrost, and I thought maybe there is a way to study that final condition of land (fluxes that were produced from land at the end) on the atmosphere.
 

wvsi3w

wvsi3w
Member
It sounds like the kind of run you're interested in is an AMIP simulation (AMIP), which has CAM and CLM actively coupled and exchanging fluxes, but prescribes SST. These are "F" compsets in CESM (FHIST, F2000clim, etc); there's a section of CESM tutorial that might help with running this: 2: Historical compset: FHIST — CESM Tutorial.
Dear Dr. Fowler,
Thank you for your response.

I understand. Do you know if "F" compsets can use an initial file from an "I" compset? Because I am waiting for my case with "I1850 compset" to finish and the restart file from my I compset is going to have important information on the condition of land and I want to use it as initial condition for the land in my future CAM_CLM simulation.

So, if I can set this aforementioned initial file in user_nl_clm of the CAM-CLM, it would be great.
 
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mdfowler

Meg Fowler
New Member
I think you can absolutely use an initial file from an I compset for the land; my hunch is this is usually what's done actually, so that the land can come into equilibrium for more slowly evolving fields like carbon pools without needing to run the full atmosphere model too. But let me know if you run into issues with that!
 
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wvsi3w

wvsi3w
Member
I think you can absolutely use an initial file from an I compset for the land; my hunch is this is usually what's done actually, so that the land can come into equilibrium for more slowly evolving fields like carbon pools without needing to run the full atmosphere model too. But let me know if you run into issues with that!
Thank you so much.
Sure, I will. I have to wait until it is finished (it is 1500 years of land simulation, will be finished in ~ two months).
 
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