This study investigates a tropospheric O₃ pollution episode over WAI and NAI in Spain and Portugal during August 2-6, 2018. The episode witnessed an abrupt rise in O₃ concentrations in both regions, exceeding regulatory thresholds. Using the WRF-CAMx model, the authors analyzed the transport mechanisms and potential sources of photochemical pollutants influencing these areas. The topic of this work is interesting, and the result is helpful for better control of O₃ pollution in these areas. However, there are still issues that need to be addressed before the paper can be considered for publication.

Specific Comments:

Line 15: has a similar approach, i.e., combing upper and lower tropospheric parameters, been used to investigate tropospheric O₃ in other studies?

Lines 25-26: need to be rephrased.

Lines 30-33: the authors mention the lack of detailed research on O₃ issues in the Atlantic Coast of the Iberian Peninsula but do not explain why studying this region is important. It would be beneficial to include a sentence to explain the significance and value of investigating O₃ problems in this area.

Lines 64-65: it would be better to explain the selection of the O₃ pollution episode in Aug 2-6 2018.

Section 3.1 focuses on the validation of meteorological variables, which is not the major target of this work. It could be better to move some less important figures and tables in this section to the supplement.

Figures 13-16: panel numbers (i.e., a, b, c) should be added and mentioned in the discussion to facilitate the audience. It could be helpful to integrate Figures 13 and 16 to show O₃ concentration evolution in 1-7 August continuously instead of 1-3 and 6-7 August in two figures. Furthermore, the discussions in this section are difficult to follow, particularly, the discussions about Figures 14 and 15.

Section 3.3: It is suggested to move the O₃ validation in this section forward because reliable simulation of O₃ concentrations is the prerequisite for the simulation-based analysis shown in Section 3.2. Figures and tables are required to be shown to demonstrate the validation results.

This manuscript presents a very detailed modeling analysis of a several-day O3 episode over the Iberian Peninsula.  A combination of the WRF and CAMx models are used to simulate the meteorology and chemistry of the episode.  The authors first compare the WRF output with existing reanalyses and station observations, and then compare the CAMx O3 with surface station data.   The model validation appears to be quite good.  The evolution of the episode is presented in great detail, in terms of both the synoptic meteorological features and the transport mechanisms for O3.  A combination of transport mechanisms appears to be present, leading to a multiday episode.  The paper is well organized and with some minor edits and technical changes, it should be ready for publication.

Minor suggested changes:

line 21:  heading --> accompanying  ?

line 70:  I'm not sure what "pathway in the Atlantic axis of the IP" means

Figure 5: ERA5 surface and 750 hPa winds for August 6 and 7 is not called in the text

Section 3.1.2:  Should point out that there is a greater observed amplitude of the daily cycle of wind speed at both Spanish stations than in the model.  But it is interesting that the reverse is true for the stations in Portugal.

line 492:   ppm-m is a rather strange unit.  How is this calculated?  Why not use something more customary for vertical columns, such as molecules per cm**2 ?   Figures 13 and 16 look like they use this unit also.

line 501: ...O3 concentrations to values exceeding....

line 605:  ...from August 2 to August 7.