General Comments:

The paper does a thorough job of reviewing the studies involving coupled Met-AQ modeling with aerosol feedback effects, but it does not provide summary of the methods used to represent ARI and ACI or any assessment of the realism of the different models. It seems important to explain various the methods used to represent ARI and ACI and give some information on their accuracy.

The paper is very long, and I found it very difficult to read through the seemingly endless recitation of statistics that have very wide ranges without any explanation for the different results.  The variety of modeling techniques, domains, resolutions, data assimilation, ICs and BCs, emissions, etc, should be considered in these comparisons.  Why such wide ranges of results?  Perhaps investigate the extremes to find out and maybe exclude studies with serious issues.

The paper needs thorough editorial review and correction

Specific Comments:

Lines 103-108:  This sentence is confusing.  Are those names of 5 models in the parentheses?

Lines 145-146: This is misleading.  While the current versions of WRF is 4.3 and CMAQ 5.3.2, these were not the version used by Wong et al 2012.  Those were WRFv3.0 and CMAQv4.7.1.

Lines 410-413: I don’t understand this sentence.  What is accounting for 80% of what?  Please clarify.

Lines 428-432:  This sentence is too long and complicated to follow.  For example, “enhanced (reduced) radiative forcing at the TOA”.  The bit in parentheses generally refers to the opposite effect on something.  What that something is, is not clear here. Is it reduced atmospheric stability and all the things in the parentheses?

Lines 493-496:  this sentence does not make sense.

Line 498: “prohibited” is not the right word.  Suppressed might be better.

Line 545: CA is use here as carbonaceous aerosols and further back as central Asia.

Line 617-621: This sentence seems self-contradictory.  Please clarify.

Line 639: Pool should be Poor.

Line 684-686: This sentence is badly worded. 

Figure 3:  Why are there so many more samples for PSI than for ARI and no-ARI?

Lines 734-735:  It seems from Figure 3 that RH2 has 2 but the SH2 has 6 not 1 PSI with ARI/no-ARI.

 Line 742: should be that rather than the

 Line 747: Figure 3 say 9 and 10 PSI with ARI/no-ARI, not 5.

Section 5.1.2:  I think this analysis needs more explanation.  Were these different studies of different lengths where the PSI were grouped according temporal scale?  Is daily scale, PSI simulations that only lasted one day? I don’t see the significance of this analysis.

Section 5.1.3:  This section is also of questionable value.  The meteorological performance of these models is more related to the physics options, FDDA, initial and boundary conditions, resolution, domain, time period, etc, of the WRF setup than whether it is WRF-Chem or WRF-CMAQ.  The meteorology performance is due to WRF not Chem or CMAQ parts.

Line 974: When reporting daily results are these day and night together?

Lines 1018-1020:  This sentence is unclear.  Which effect increased (decreased)?

Lines 1020-1022: Again, doesn’t make sense.  Trying to say too much in single sentences.

Lines 1056:  what increase (decrease)?

Lines 1079-1081:  Way too many parentheses constructs.  Can’t follow.

Line 1108: severe rather than server?

Review of  “Two-way coupled meteorology and air quality models in Asia: a systematic review and meta-analysis of impacts of aerosol feedbacks on meteorology and air quality,” by Gao et al., submitted to Atmospheric Chemistry and Physics Discussions.

This paper reviews air coupled meteorology-air quality models applied to Asia. It is quite detailed, almost too much in parts of it. It could benefit from more organization, better figure captions, and more specific conclusions. Below are some additional comments.

Introduction. “Online models or coupled models are designed and developed to consider the two-way feedbacks and attempted to accurately simulate both meteorology and air quality.” It seems that this would be a good place to identify the origin of such models. According to Zhang (2008), the GATOR-GCMOM model is “the first fully-coupled online model in the history that accounts for all major feedbacks among major atmospheric processes based on first principles (Jacobson, 1994, 1997; Jacobson et al., 1996).”

Introduction. “Currently, there are three representative two-way coupled meteorology and air quality models.” What does that mean? There are several more two-way coupled meteorology and air quality models, as cited later in the paragraph.

Introduction. Another coupled air quality-meteorological model used in Asia is GATOR-GCMOM. Its applications have included a study of the local and global fate of radionuclides from Fukushima (Ten Hoeve and Jacobson, 2012), where the model was run in both nested and global mode, and studies of the impact of urbanization in Beijing (Jacobson et al., 2015) and New Delhi (Jacobson et al., 2019) on air quality and meteorology. It seems that these papers meet the criteria listed.

The discussion could be improved by identifying how different models treat aerosol size and composition. Do they use lognormal modes or discrete size sections. How many size distributions in either case are treated? What aerosol physical processes are treated? Coagulation? Condensation/evaporation? Internal-aerosol thermodynamic equilibrium? Hydration?

How are clouds treated in the models? Are they treated with lognormal modes or discrete size distributions or without size information? How do clouds interact with aerosol particles?

Figure 6, caption. “…using two-way coupled models in Asia from literature.” Please identify exactly which models are included and where the results are applicable to in the figure caption. Same with other captions.

In the figures, it would be useful to know what the overall mean percent error is in addition to the absolute errors

Figure 9. Please provide details of the models used and the region covered.

Overall, it is difficult to determine what the main scientific takeaways from the paper are. Are the existing models sufficient to provide reliable estimates going forward? What are the main limitations and strengths of the models?

References:

Jacobson M. Z. (1994). Developing, coupling, and applying a gas, aerosol, transport, and radiation model to study urban and regional air pollution, Ph. D. Dissertation, Dept. of Atmospheric Sciences, University of California, Los Angeles, 436 pp.

Jacobson, M. Z., R. Lu, R. P. Turco, and O. B. Toon, Development  and application of a new air pollution modeling system. Part I: Gas-phase simulations, Atmos. Environ., 30B, 1939–1963, 1996

Jacobson, M. Z., Development and application of a new air pollution modeling system. Part III: Aerosol-phase simulations, Atmos. Environ., 31A, 587–608, 1997

Jacobson, M.Z., S.V. Nghiem, A. Sorichetta, and N. Whitney, Ring of impact from the mega-urbanization of Beijing between 2000 and 2009, J. Geophys. Res., 120, 5740-5756, doi:10.1002/2014JD023008, 2015

Jacobson, M.Z., S.V. Nghiem, A. Sorichetta, Short-term impacts of the mega-urbanizations of New Delhi and Los Angeles between 2000 and 2009, J. Geophys Res., 124, 35-56, doi:10.1029/2018JD029310, 2019

Ten Hoeve, J.E., and M.Z. Jacobson, Worldwide health effects of the Fukushima Daiichi nuclear accident, Energy and Environmental Sciences, 5, 8743-8757, doi:10.1039/c2ee22019a, 2012

Zhang, Y., Online-coupled meteorological and chemistry models: history, current status, and outlook, Atmos. Chem. Phys., 8, 2895-2932, 2008.