Feasibility for cross-regional simulations

CMAQ
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Hi everyone,

I’m currently exploring whether it is feasible to use WRF-CMAQ driven by CMIP6 meteorology together with the HTAPv3 emission inventory to simulate air quality across different regions of the Northern Hemisphere (for example, China and the US). The idea is to have a consistent framework that would allow for cross-regional comparisons of air quality trends under different climate scenarios.

However, I’m also aware of several potential limitations, such as the relatively coarse resolution and possible biases in CMIP6 meteorology after downscaling and possible differences in how well the chemical mechanisms perform across different environments (maybe I need to use different parameterization schemes?). It is also worth noting that the latest HTAPv3.1 release now incorporates MEIC for China and EPA for the US, which should improve the reliability of simulations in these regions？

My main questions are: do you think this framework is reasonable for comparative studies across regions, and what other caveats or considerations should I keep in mind?

Thanks in advance for your thoughts!

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This is something that has been done before (e.g., Evaluation of near surface ozone and particulate matter in air quality simulations driven by dynamically downscaled historical meteorological fields - ScienceDirect ). Popular approaches on the meteorological side include dynamical downscaling, where a regional model like WRF is driven by a CMIP GCM, and “pseudo global warming” where the thermodynamic change from multiple CMIP models is averaged and applied to WRF. Each approach has pros and cons depending on the hypothesis being tested, and it’s non-trivial to do either correctly.

I’m not sure about HTAP.

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Thank you very much for your detailed reply.

One additional concern I still have is whether it is feasible to use HTAPv3 emissions combined with CMAQ to simulate source-specific PM2.5 contributions (via zero-out source apportionment) consistently across different world regions (e.g., China and the US), and then directly compare the trends. From what I have seen, most studies tend to focus on a single region, such as China or the US, but cross-regional source-comparative analyses seem to be relatively rare.

Do you think such a setup would be methodologically sound, or are there hidden pitfalls I should be aware of when combining HTAP with CMAQ for multi-region comparisons? And for parameterization schemes in different regions, would it generally be reasonable to follow what has been used in past studies?

Thanks again for your insights！