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spinup problem of CLM5-BGC with VR grid

BoHuang

New Member
Dear all,

recently, I am working on the spinup simulation of CLM5-BGC with a VR grid. I want to explore the bio-geochemistry effect of recent land cover change in Europe. I produce the VR grid (1/4 degree in Europe region and 1 degree out of Europe) and generate the surface data. I replaced the land cover data with new ESA satellite dataset. Following the BGC-spinup case (1.5.5. Spinup of CLM5.0-BGC-Crop — ctsm release-clm5.0 documentation), I run AD mode (200 years), then post-AD mode (400 years). However, some dis-equilibrium grids locate in my key research domain (north Scandinavia).

1) Should I prolong the simulation to force the grids to reach equilibrium, or I can use the restart file to run a normal coupled simulation (compset: FHIST_BGC)?
2) I want to see the biogeochemistry effect change between 1992 and 2015. Should I follow the same approach to run the spinup simulation (AD mode and Post-AD mode) with land cover data 1992 and 2015, or I can use the restart file from 1992 simulation to initialize the simulation with land cover 2015?
3) Friedlingstein et al. (2019; Global Carbon Budget 2019) presented the carbon budget including the vegetation carbon (450-650 GtC) and the soils carbon (1500-2400 GtC). The total soil carbon (TOTSOMC) is ca. 3170 GtC in my post-AD simulation. The number seems much lager than the soil carbon budget. Should I change some parameters and re-run the spinup simulation?

Greetings,
Bo
 

oleson

Keith Oleson
CSEG and Liaisons
Staff member
1) As noted in the User's Guide, it can be difficult to achieve global equilibrium in post-AD mode in less than 1000 years. It is not surprising to see dis-equilibrium at northern latitudes due to the cold temperatures. That being said, you can define equilibrium criteria based on your research goals.

2) I think you could potentially shorten your overall spinup time for the 2015 simulation by using the restart file from 1992 to initialize the 2015 simulation, this will depend on how different the 1992 and 2015 landcover are. I would still spinup using the AD/post-AD approach however.

3) The equilibrium global TOTSOMC can be a strong function of the atm forcing data being used. For example, "Because of the greater permafrost extent and colder permafrost soil temperatures in CLM5 when forced by CRUNCEPv7 than by GSWP3v1, the stocks of soil C to 3‐m depth are a factor of 2 larger when forced by CRUNCEPv7 (4,000 Pg C) than when forced by GSWP3v1 (1,925 Pg C), demonstrating the extreme sensitivity of simulated permafrost soil C stocks to simulated permafrost conditions." (Lawrence et al. 2019, JAMES).
 

BoHuang

New Member
Hi Keith,

thank you very much for your reply and suggestion. It is really helpful.

Greetings,
Bo
 
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