Soil Carbon spin up with crops

[rambhari01]

Dear CESM user/help,

We are planning to run 2 atmospheric only control runs for 1850, with coupled land (using F compset) using CESM2.2.2 and cases are created using the compset "

1850_CAM60_CLM50%BGC-CROP_CICE%PRES_DOCN%DOM_MOSART_SGLC_SWAV".

In these 2 runs, First would be the 1850 control with the crops as true (active) and in second, crops would be turned off using "crop_use=.false." and omitting the "-crop" in env_run.xml file.

In the both of these case, CLM model get this below file as clm initial conditions assigned to it.

"finidat = /scratch/rs9552/inputdata/lnd/clm2/initdata_map/clmi.B1850Clm50BgcCrop.0161-01-01.0.9x1.25_gx1v7_simyr1850_c200729.nc"

We have following questions for this experiment setup:

1.) Does the initial condition file for 1850CAM-CLMBGC_Crop include a carbon spinup for 1850 crops? In other words, are the soil and vegetation carbon pools equilibrated for pre-industrial conditions?
- We believe that this is true as the main B1850 run (control run from which clm initial file came) has used the crop_use=true. Please confirm.

2.) For the second 1850 control run, Is there any initial condition file 1850CAM-CLMBGC_Crop with carbon spinup that has crops turned OFF?
If not, how can we create a carbon spinup we start with using the same initial condition file mentioned above?
I guess, if we run use the CLM_ACCELERATED_SPINUP=on ? and then switch to a control run? How long we need to run these sequence in order to get a spun up control run for carbon with crops turned off?


Apart from these another question regarding the CLM vegetation,

3.) Are the vegetation types pre-assigned to a grid cell or is there changing biogeography of vegetation?


Thank you
-R

 

[oleson]

1) Yes
2) No. Ideally, you would do an I-case spinup (CLM_ACCELERATED_SPINUP=on, then a normal run using the initial file from the end of the accelerated spinup run) forced with coupler history (atmospheric) forcing taken from an F-case that has the same land configuration as the I-case. And then use the initial file from the end of that to start your F-case. But I assume you probably don't have coupler history forcing available. Alternatively, you could do an I-case spinup forced by reanalysis (GSWP3v1 is the default) with crops off and then use the initial file at the end of that to initialize your F-case. You'd want to run the F-case for 10-20 years before using data for analysis to allow the land to equilibrate to the different atmospheric model forcing.
There is some information on I-case spinup here:

1.5.5. Spinup of CLM5.0-BGC-Crop — ctsm release-clm5.0 documentation

To meet strict equilibrium criteria in an I-case spinup, AD usually takes about 300 years, and post-AD can take around 1000 years. But you should decide what's really important to spinup, maybe you don't need deep soil carbon at high latitudes to be spunup, which takes the longest amount of time.

3) Vegetation types are fixed in an 1850 configuration. They can change in a historical simulation, but the changes are prescribed using a landuse timeseries file.