Default Restart Files for B_1850-2000_CAM5 Compset

[skc48@cornell_edu]

Hi,

I am looking to run cesm1_2_0 with a f19_g16 grid using the B_1850-2000_CAM5 compset starting in 1850. I just wanted to confirm; under the default setup are the restart files fully spun up?

Thanks,

Spencer

 

[hannay]

Hi Spencer,B_1850-2000_CAM5  is not a scientifically validated configuration. Usually, we ran 20th century with the comspet B_1850-2000_CAM5_CN.The difference between B_1850-2000_CAM5 and B_1850-2000_CAM5_CN is that in the second compset the Carbon-Nitrogen cycle is turned on. This is the standard way to run CESM in coupled mode. I recommend that you switch to a  B_1850-2000_CAM5_CN compset except if you have good reasons not to.If you use the compset B_1850-2000_CAM5_CN, the initial condition will come from "b40_1850_2d_r07c5cn_160jp" and i expect this to be close to be spunup. However, I would recommend that you run first a 1850 control B_1850_CAM5_CN starting from "b40_1850_2d_r07c5cn_160jp" and make sure there is no drift and the top of the atmosphere is well balanced. Then, you can start your 20th century run.The compset  B_1850-2000_CAM5 uses the case "b40_1850_c02c_76jpf" for initial conditions and I don't expect this to be spunup. We just provided initial conditions so the model runs. If you want to stick with the B_1850-2000_CAM5 (without CN), I would recommend that you also run a 1850 control starting from "b40_1850_2d_r07c5cn_160jp" (adjust the TOA radiative balance and spinup the model). Then, you can start your 20th century run.Cecile   

 

[skc48@cornell_edu]

Hi Cecile,Thank you for your reply. Per your recommendation I'll go the route of using a B_1850-2000_CAM_CN run after running a control using the B_1850_CAM_CN compset to verify that the top of the atmosphere is well balanced. Spencer

 

[jindachao@gmail_com]

Dear Hannay,
You said the B_1850-2000_CAM5 is not a reasonable configuration, so how about B_2000_CAM5? Best wishes, Dachao Jin

 

[hannay]

We don't validate the B compset without CN. I didn't say the B_1850-2000_CAM5 is not a reasonable configuration but the climate hasn't been validated. So you need to check that the climate is reasonable. It is the same for  B_2000_CAM5.The list of scinetifically validated configurations is available at:https://www2.cesm.ucar.edu/models/scientifically-supported

 

[zhu467@purdue_edu]

Hi Hannay,I am just using B20TRC5CN compsets, but I find a problem that when I use the transient co2, the co2 in the lnd.log file shows it has a value of 355ppm but not the co2 level at 1850. I use the default setup and model run from 1850. So I think there might be something wrong with the data transfer. Information in the lnd.log file atmospheric forcing data is from cesm atm model
 Restart parameters:
    restart pointer file directory     = .
    restart pointer file name          = rpointer.lnd
 Large file support for output files is ON
 model physics parameters:
    CO2 volume mixing ratio   (umol/mol)   =    355.000000000000     Best.

 

[hannay]

I would expect that you would get:  CO2 volume mixing ratio                = diagnostic      Please could you check your land namelist (lnd_in). What is the value of the variable: "co2_type" co2_type = 

 

[zhu467@purdue_edu]

Yes, co2_type is diagnostic, which uses co2 from ATM component.

 

[zhu467@purdue_edu]

I think if this is really a bug for the current version model, all of the user using the fully coupled mode should take serious of this problem. It will cause great error.

 

[klindsay]

Hi,The value reported on the line 'CO2 volume mixing ratio' is misleading when co2_type is diagnostic. There is a variable in the CLM output named PCO2. It is the CO2 value used by the land model, in units of Pa. CO2 in ppmv is 1e6*PCO2/PBOT. This expressions is consistent with co2vmr used by CAM.Keith