initialization data in IHistClm45Bgc

[Wang Jingjing]

I used the CLM tool to create surface data in 1980-2015, and want to use the IHistClm45Bgc module to understand the changes of soil organic carbon caused by land use change. However, initialization data (finidat) is lacking. Which of the following way is the more reasonable way to obtain initialization data.

1、The IHistClm45Bgc module was spin up to the equilibrium state by using the surface data in 1980-2015 (fsurdat and flanduse_timeseries) and the meteorological data in 1979. Then, the final land surface result is used as the initialization data (finidat).

fsurdat = ‘surfdata_0.23x0.31_hist_78pfts_CMIP6_simyr1980_c230302.nc’
flanduse_timeseries = ‘landuse.timeseries_0.23x0.31_hist_78pfts_CMIP6_simyr1980-2015_c230302.nc’


2、The IHistClm45Bgc module was spin up to the equilibrium state by using the surface data in 1979 (fsurdat and flanduse_timeseries) and the meteorological data in 1979. Then, the final land surface result is used as the initialization data (finidat).

fsurdat = ‘surfdata_0.23x0.31_hist_78pfts_CMIP6_simyr1979_c230302.nc’
flanduse_timeseries = ‘landuse.timeseries_0.23x0.31_hist_78pfts_CMIP6_simyr1979-1979_c230302.nc’

 

[oleson]

I'd recommend using the new version of the model, CLM5.
If you aren't making any changes to the model then you could analyze existing simulations, see here for location of data:

Output & Diagnostics | Community Earth System Model

www.cesm.ucar.edu

These include full historical simulations.
If you are modifying the model and can't run a full historical for some reason, then we usually recommend using at least more than one year of atmospheric forcing, e.g., 10-20 years prior, to introduce some interannual variability. You could just use the 1979 surface dataset, or a surface dataset year that is somewhere in between your years of forcing. I don't think I would spinup with 1980-2015 surface data, you generally want to precondition the model with year(s) prior to the start of your simulation.
On the other hand, if you going to spend computer time spinning up anyway, then perhaps run the full historical where there is an appropriate initial file available.