co2 flux and atmospheric co2

[ckcastillo@purdue_edu]

Hi!
I just wanted to clarify if and how the CO2 exchange / flux (FCO2) determined by the land model gets included in calculations of atmospheric CO2 (CO2_PPMV) in a fully-coupled mode. It seems that atmospheric CO2 conc. is pretty much set by namelist parameters of CAM.

Thanks!

 

[slevis]

You may wish to also post this in a cam or ccsm related thread for more visibility. I'm not sure how to answer your question myself because I have not tried a run with interactive atm co2.

In ccsm4 (to be released next year), there will be clear instructions on how to do this.

Sam

 

[ckcastillo@purdue_edu]

Just a related question - in the case that we do want to prescribe CO2 conc. in a fully-coupled mode, do we have to change pco2 in clm in addition to co2_vmr in cam? I thought that this may not be necessary but pco2 seems to be hard-coded as a constant in clm_varcon and CanopyFluxes so just thought I'd check. Thanks!

 

[slevis]

In older versions of the clm you did have to change the co2 by hand, and it sounds as though this is true in your version.

Sam

 

[ckcastillo@purdue_edu]

How would this work though for settings such as Ramp_CO2_only and the IPCC modes of CCSM3? I would assume there's some way that CLM pCO2 gets updated at the appropriate time steps?

 

[slevis]

I'm not sure, but I have a feeling that the physiological effects of changing atmospheric co2 were not accounted for.