This study provides a very interesting modelling study of the potential global impacts of changing agricultural demand, and thus ammonia emissions, on future surface ozone concentrations. The study provides a comprehensive set of scenarios looking at different vegetation responses to increased fertiliser use on ozone concentrations between 2000 and 2050, using both prescribed and dynamic meteorology. Overall it was shown that increased nitrogen fertiliser use by 2050 leads to increased LAI and thus enhanced surface ozone concentrations, with the biggest impact seen when dynamic meteorological affects were allowed. This study is suitable for publication in ACP after the following comments are addressed.

Specific Comments

Does this version of the CLM include the impacts and feedbacks of ozone damage on stomatal resistances? If so were they included in the simulations preformed in this work? This could potentially have further impacts on the nitrogen deposition effects on vegetation, particularly through stomatal uptake.

In Section 5 the authors present a very good summary of the potential feedbacks caused by changes in nitrogen deposition in response to future changes in agricultural practices. In particular they focus on the feedbacks through changes in LAI and canopy height. However, they do not cover the potential feedbacks involved where changes in ozone concentrations could lead to plant damage and thus impacts on not only ozone concentrations themselves but also uptake of nitrogen species. It is appreciated that given the current setup of the modelling system a further simulation is not possible but would the authors be able to give a more detailed comparison with the potential effects of ozone damage on the results observed or comment on how this could affect the results simulated by the model.

Technical Comments

Page 1, Line 24: Please change to emissions

Page 2, Line 4: The start of this sentence seems a little repetitive, please correct to something like ‘Crops typically take up only about 40-60% of the nitrogen fertiliser applied…….’

Page 5, Line 13: Do you mean Fig 2 here?

This manuscript presented a modelling study that aimed to quantify how future changes in atmospheric nitrogen deposition as driven by rising agricultural food production affect surface ozone levels via air-biosphere interactions. Asynchronously coupled air-biosphere modelling simulations were conducted using the atmosphere and land components of the Community Earth System Model (CESM), so that the individual biogeoschemical and biogeosphysical pathways of the nitrogen deposition-surface ozone air quality linkage. The results emphasize the importance of biogeophysical pathways or the meteorological variations induced by vegetation changes in modulating surface ozone.

The manuscript is overall well conducted and presented. The simulations are well designed, and the analyses identify a new linkage of agricultural nitrogen and air pollution. I suggest publish on ACP after the following comments been addressed.

Specific comments:

1) Page 5, Eq. 1:

A few more sentences describing the growth factor are suggested. How it treats different crops? Could it consider ammonia emission factors may be different for different crops? Please clarify.

2) Page 5, Line 20:

Each atmospheric chemistry simulation was conducted for 20 years. What meteorology fields were used to represent the 2000 and 2050 conditions? Please clarify.

3) Page 9, Line 29:

“Ozone dry deposition velocity decreases by 0.002-0.004 …”. Should it be increases in ozone dry deposition velocity as shown by figure 5?

4) Page 11, Figure 6:

It appears that the individual effects do not add up when with dynamic meteorology. As shown in this figure, ozone changes due to LAI (figure 6d) and due to HTOP (figure 6g) show large positive values in the central US, while the combined effects (due to ALL, figure 6m) become much weaker. The same issue can be seen for deposition velocity changes over the US (figure 6f/i/6o). Can you explain why?

5) Page 11, Line 15:

“increase local albedo, which results in enhancement in absorbed solar radiation”. It is not clear why higher albedo could lead to higher absorbed solar radiation, as higher albedo tends to reflect more solar radiation back to the atmosphere. Please clarify.

6) Page 11, Line 22: Wang et al. (2020) is not listed in the References;

Page 12, Figure 7: There are two (f) panels in the figure;

Page 16: Line 26-31, missing journal and page information for the two citations.