Comprehensive Air Quality Model with Extensions: Formulation and Evaluation for Ozone and Particulate Matter over the US
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsReview of the paper: “Comprehensive Air Quality Model With Extensions: Formulation and
Evaluation for Ozone and Particulate Matter Over the US”
This paper core functionality of CAMx v7.20, provides a thorough overview of CAMx’s capabilities and applications and demonstrates an example of predicted regional and seasonal ozone and PM2.5 by summarizing a model evaluation from a recent 2016 national-scale CAMx application with specific focus on ammonia treatments. Since CAMx is a mature and well-established tool in the field of air quality modeling, across various sectors (government, industry, academia), detailed overview of the processes involved within the model and clearer communication of new features was lacked, this paper well needed to enhance the model’s utility and user experience. Overall, the scientific quality of the paper is good. It is written clearly and has a logical and structured structure. The model simulations and evaluations are well described and reasonable. I can therefore recommend the paper for publication in any case and have only a few comments that should be taken into account.
The introduction provides a foundation for understanding CAMx and list some of its features. Author can strengthen the introduction/manuscript by discussing the current challenges in air quality modeling and how CAMx v7.20 addresses these issues and highlighting particular strengths of CAMx over other models to justify its use in future studies. Or while mentioning similar CAMx result to CMAQ results is useful in the conclusion expanding on how CAMx v7.20 might offer advantages over CMAQ or other models. What differentiates CAMx, and why should one consider using it over other models? It would be beneficial mention if the CAMx model was involve in any intercomparison modeling projects to highlight its performance compared to other model in term of accuracy and running time and in case has been using in any air quality forecast operational systems.
The integration of WRF MSKF and CAMx CiG provides a coherent framework for modeling cloud processes and their interactions with atmospheric chemistry. This sub-grid cloud framework is particularly valuable for more accurately simulating deep convective transport, aqueous chemistry, and wet scavenging, which occur at scales smaller than the model's grid resolution. This is crucial for accurate predictions in regions with complex cloud dynamics. Defining the physical attributes of a stationary, steady-state sub-grid cloud for an hour how realistic it is for convective and stratiform clouds? Have you validated the model's performance by comparing its predictions with observational data using CiG? How is the overall computational cost of the model for large scale of the simulation?
The general model's predictions are compared against data from several ambient air quality monitoring networks. It is nice author put specific attention for model evaluation of PM speciation in cold season, Can author also show or reference to any case studies from specific events (e.g., wildfires) done by CAMx to help validate or challenge the model's assumptions, particularly in events/regions with high/unique emission sources.
The planned updates for CAMx are promising, but the conclusion does not provide enough context to understand how these updates will address the current model's limitations. It would have been beneficial to discuss how these updates are expected to improve specific aspects of the model’s performance, especially for PM2.5. When mentioning future updates, provide specific examples of how these changes are expected to improve the model's performance.
The conclusion is generally clear, but it is somewhat vague in certain areas. For instance, the statement that PM2.5 statistical performance "fluctuated around statistical criteria" could be more precise. What does "fluctuated" mean in this context? Were there significant deviations, or were they mostly minor?
Edit Line 856 - (Figire 15).
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript mainly introduces the core functions of the CAMx v7.20 comprehensive air quality model and the model evaluation of ozone and fine particulate matter (PM2.5) in the entire region of the United States. The manuscript also mentions the development and improvement of this model and cites the detailed model construction, input/output requirements and application guidance in the user guide.
Main comments:
1. Section 2.6.2 of the manuscript mentions the calculation method of photolysis rates, that is, by externally assuming clear sky conditions and deriving photolysis rates according to five parameters (solar zenith angle, ground height, total ozone column, surface albedo, and terrain height), but does not involve uncertainty analysis of these rates. Please specifically elaborate on how you considered the uncertainty of photolysis rates when choosing to use the SOAP module.
2. This manuscript mainly uses input data from meteorology and monitoring stations to predict ozone and PM2.5 concentrations. And the chapter 2.6.4. Aerosol Chemistry mainly only mentions the aerosol chemical changes of PM2.5. Relevant explanations on ozone are also hoped.
3. Although the chemical effects of some precursors are mentioned, the data mainly comes from atmospheric environment data rather than emission data. The authors also mentioned the influence of primary organic aerosol (POA) on the chemical evolution of secondary organic aerosol (SOA) in lines 538-540 of the manuscript “However, POA does influence the chemical evolution of SOA.”, and pointed out that an updated SOAP scheme is being developed and tested. Sincerely hope that this will be reported in future research.
4. There is an unwanted highlight at the reference citation in line 496. Please check and delete the highlight.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe paper is well written and interesting to read, however I see the following issues that should be resolved before publishing this paper:
1. Line 766-769: "Causes for higher winter concentrations may be related to more stable, less-mixed meteorological conditions trapping mostly primary PM2.5 as chemical production of secondary aerosols and seasonal evaporative VOC emissions are minimized. Conversely, causes for higher summer concentrations may be related to elevated chemical production and higher evaporative emissions from mobile and biogenic sources. Authors should add references for supporting the sentences.
2. When authors state "Warm Season or Cool Season" please add information of meteorological data for comparison includes weather factors such as temperature and humidity, wind speed and strength, precipitation.
Author Response
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Reviewer 4 Report
Comments and Suggestions for AuthorsGeneral comments:
The research updated the formulation and mechanism of CAMx. Interestingly, the new model evaluated the ozone well over the US, providing reasonable confidence for the model user. For modeled PM2.5, even though the model performance varies among different regions, it allows the model user to narrow the research gap. However, several points need to be clarified. The reviewer suggests the paper be accepted for publication after several minor comments have been revised.
Minor comments:
Is the current version of CAMx doing well compared to the previous version? Also, the authors are suggested to highlight the importance of CAMx7.20 in the introduction section. What is the limitation of the last CAMx that needs to be improved in the present version? In Lines 288-289, what has been updated for the dry deposition on the ocean? Please provide the revised formulation of ocean ozone resistivity.
Author Response
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Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for addressing all comments and incorporated the suggested changes. I believe the manuscript is ready for publication in its current form.
Author Response
Thanks for your comments.
