Hi All,
I used CMAQ v5.0.2 with cb05tucl-ae6-aq mechanism to run my model. Then I used CMAQ v5.5 with cb6r5_ae7_aq mechanism with the same input files including MCIP, Emissions, … But the results of these two case are different like the concentrations of CO and O3 is around 10% and 20% more in the CMAQ v5.5 case, respectively.
Is this logical or related to the difference versions of CMAQ and Mechanisms?
Thanks
Changes in the model versions is likely to yield large model differences in species. Since CMAQ is a holistic air quality model, which tries to represent the major processes in the atmosphere, it’s likely that changes to the sources and sinks of different pollutants in different versions are causing these changes, which is likely logical depending on how you ran the model – especially if you are comparing model versions that are 7-10 years apart.
My recent experience, when comparing only mechanism sensitivities (i.e., CMAQv5.5 with CB6 vs CB05) on a hemispheric setup found that CO is consistently lower throughout the model domain (both vertically and horizontally) in CB6. However, O3 is generally higher. A good resource to understand only the mechanism changes between CB6 and CB05 is here: https://www.eoas.ubc.ca/courses/atsc507/ADM/cmaq/cb6.pdf.