Comparison of Online and Offline simulations

I simulated a temperature inversion episode and I expected that the concentrations in Online simulation were larger than offline simulation, but it didn’t. Could you help me why this happened, please?
I use WRFv3.8 and CMAQv5.2. The year is December 2017 and my resolution is 3 km for the urban domain.
Thank you


The coupled model mainly alters the amount of SW radiation reaching ground due to presence of aerosol in the atmosphere (please refer to the coupled model paper published in 2012). Such change impacts surface temperature, PBL height as well as photolysis rate. It is true that reduction of PBL height increases the concentration level of chemical species when the amount of chemical species unchanged but this does not represent the complete picture. Furthermore, according to your provided result, it shows the coupled model result is closer to observation in general, i.e. the coupled model performed better than offline model.


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Hi David,

Thank you for your reply. I did another simulation. I ran WRF-CMAQ one-way model and used its WRF outputs to running the offline CMAQ model. I reached the same result. The pick point in the Offline model (CMAQ) is higher than the Online model (WRF-CMAQ one-way and two-way). What is the difference between these two models? Could you guide me, please?
Thank you.

Best regards,

Hi Ensiyeh,

Please read this article: Wong, D.C., Pleim, J., Mathur, R., Binkowski, F., Otte, T., Gilliam, R., Pouliot, G., Xiu, A., and Kang, D. (2012). WRF-CMAQ two-way coupled system with aerosol feedback: software development and preliminary results. Geosci. Model Dev., 5, 299-312.