methane from CLM?

[mvparke@sandia_gov]

Hello,I am running CESM (1.2, rel 06) with the compset FMOZMAM (F_2000_MOZMAM_CN). I'm trying to identify all the sources of methane in my simulation and systematically remove them to ensure that I understand where methane is coming from. So far I've found methane in the cam lower boundary conditions file (flbc_file) and generated from atmospheric chemistry reactions -- but I still have a significant amount of methane present after I have removed methane from those two sources. I'm wondering if I have methane coming from the land model, but I don't know where to look for that. Can anyone help?Thanks in advance for your assistance! Marie

 

[oleson]

Depending on the namelist settings, the methane flux may be included as an adjustment to NEE and/or as a separate flux to the atmosphere (as far as I can tell).You could look in clm_atmlnd.F90 for "gch4%nem(g)", which adjusts the flux of CO2 by the net conversion of mineralizing C to CH4.
And look at "flux_ch4" in ch4Mod.F90.  This is variable "FCH4" in the land history files (gridcell surface CH4 flux to atmosphere).  I'm not quite sure how to tell if the atmosphere is actually receiving and using this flux.

 

[mvparke@sandia_gov]

Thanks for those suggestions, oleson. It looks like ch4Mod.F90 (and other methane-related code) are present in clm4.5 but not clm4.0. I've had trouble running clm4.5 (I can't set up the case, see my post at https://bb.cgd.ucar.edu/running-clm45-cesm12) and haven't been able to track any methane coming from land in clm4.0. It sounds like CLM4.5 is going to be the key to determining how much methane is entering the atmsophere through the land model. I think my next step here is to figure out how to run a simulation with CLM4.5 (using CESM1.2_rel06). If you have any insights or suggestions I'd really appreciate them!Thanks,Marie