Dear CMAQ users,
I am currently working on implementing methane (ECH4) as an additional variable in the CMAQ v5.0 adjoint model to evaluate sensitivities. The chemical mechanism used is CB05CL_AERO5. I have successfully modified the chemical mechanism files (i.e., GC_cb05cl_ae5_aq.csv, GC_cb05cl_ae5_aq.nml, and GC_SPC.EXT) to include ECH4 and can now output its concentration without any issues.
In particular, I added the following two chemical reactions:
OH + ECH4 = MEO2 # 2.45E-12 @ 1775K
CL + ECH4 = HCL + MEO2 # 6.6E-12 @ 1240K
Initially, a background CH4 concentration was used, but I have modified the model to utilize CH4 emissions as input, and this successfully drives the ECH4 concentration field.
However, when incorporating these reactions into the Tangent Linear and Adjoint models by modifying KPP-related subroutines (KPP_Function, KPP_Jacobian, KPP_JacobianSP, KPP_LinearAlgebra), I encountered an issue where NaN values appear in the computed concentrations. I suspect the problem may lie in the hard-coded Jacobian structure in KPP_Jacobian.f90, which might be incompatible with the changes I’ve made.
Would anyone be willing to provide insight or guidance on resolving this issue? Any help would be greatly appreciated.
Thank you in advance.
Sincerely,
Jeong hyeok