Description
A few issues with the implementation of the Sulfur Tracking Method (STM) in CMAQv5.4 have been identified. These are as follows: (1) Not all chemical mechanisms that predict organo-sulfate species have been included in the list of mechanisms for which STM should also track “OSO4” species. (2) The model makes erroneously low ASO4GAS tag predictions. (3) Due to the aerosol-to-aqueous (AE2AQ) surrogate chosen for ABR, there will be differences between STM and non-STM model results for the cb6r5m_ae7_aq mechanism.
Scope and Impact
If employing the STM in CMAQv5.4, your SO4 tags will be incorrect due to the severe underprediction of the ASO4GAS tag. If running STM with a chemical mechanism that has organo-sulfate species but is not included in the list of mechanisms for which STM should calculate “OSO4” tags (i.e., cb6r5_ae7 and cracmm mechanisms), said “OSO4” tags will not be included in the model output. Predictions with STM for the cb6r5m_ae7_aq mechanism will be incorrect and will differ from the base model results.
Solution
The solution to the first issue is to add the cb6r5_ and cracmm mechanisms to the STM-related lists regarding OSO4 tagged species in the following files: AERO_DATA.F, CGRID_SPCS.F, and convcld_acm.F.
The solution to the second issue is to swap the order of the calls of PA_UPDATE_AERO and STM_WRAP_AE after the AERO call in sciproc.F.
Until a fix has been implemented to update this and other aerosol-to-aqueous surrogates, it is not recommended to use STM with the cb6r5m_ae7_aq mechanism at this time.
Additional context
A pull request has been prepared and is under review to address these issues.
Description A few issues with the implementation of the Sulfur Tracking Method (STM) in CMAQv5.4 have been identified. These are as follows: (1) Not all chemical mechanisms that predict organo-sulfate species have been included in the list of mechanisms for which STM should also track “OSO4” species. (2) The model makes erroneously low ASO4GAS tag predictions. (3) Due to the aerosol-to-aqueous (AE2AQ) surrogate chosen for ABR, there will be differences between STM and non-STM model results for the cb6r5m_ae7_aq mechanism.
Scope and Impact If employing the STM in CMAQv5.4, your SO4 tags will be incorrect due to the severe underprediction of the ASO4GAS tag. If running STM with a chemical mechanism that has organo-sulfate species but is not included in the list of mechanisms for which STM should calculate “OSO4” tags (i.e., cb6r5_ae7 and cracmm mechanisms), said “OSO4” tags will not be included in the model output. Predictions with STM for the cb6r5m_ae7_aq mechanism will be incorrect and will differ from the base model results.
Solution The solution to the first issue is to add the cb6r5_ and cracmm mechanisms to the STM-related lists regarding OSO4 tagged species in the following files: AERO_DATA.F, CGRID_SPCS.F, and convcld_acm.F.
The solution to the second issue is to swap the order of the calls of PA_UPDATE_AERO and STM_WRAP_AE after the AERO call in sciproc.F.
Until a fix has been implemented to update this and other aerosol-to-aqueous surrogates, it is not recommended to use STM with the cb6r5m_ae7_aq mechanism at this time.
Additional context A pull request has been prepared and is under review to address these issues.