WRF_VPRM have no negative value in CO2_BIO and CO2_OCE

[pwang18]

Hi there,
I ran WRF_VPRM recently but got all positive values in CO2_BIO and CO2_OCE. It should have some negative values but seemed to just output the values larger than zero.
Any suggestion is appreciated.

namelist.input is attached.

 

[jordanschnell]

Hi,

I believe these quantities are concentrations, so cannot be zero. Are you interested in the fluxes? e.g., see this line in module_ghg_fluxes.F

chem(i,1,j,p_co2_bio)= chem(i,1,j,p_co2_bio) + conv_rho* (eghg_bio(i,1,j,p_ebio_gee) + eghg_bio(i,1,j,p_ebio_res)) ! both uptake and release

Jordan

 

[Michal_Galkowski]

Dear Pwang,

You should add a constant offset to both initial and boundary conditions, e.g. 400 ppm.

Kind regards,

Mike Galkowski
MPI-BGC Jena

 

[yuanfangcan]

Dear Pwang
Mike is right.
I believe what really happened is that the advection scheme is positive definite. So the model indeed only keeps positive concentrations.
So to solve this issue, either adding a constant offset to both initial and boundary conditions, e.g. 400 ppm, as Mike said.
or using global CO2 simulation outputs (e.g., CarbonTracker) as initial and boundary conditions, as we did in our regional simulations: https://doi.org/10.1029/2019MS001875

Cheers!
Xiao-Ming Hu