Dear authors,

I am still waiting for a couple of additional reviews before reaching a final decision on the manuscript. However, I would like to alert the authors that, in my assessment, the manuscript does not yet provide a sufficiently convincing argument regarding the novelty and quantitative contribution of the work.

The role of tropopause folding and stratosphere–troposphere exchange (STE) in producing elevated ozone concentrations in high-elevation subtropical regions has been discussed for decades in the literature, including studies of ozone intrusions associated with upper-level troughs, cutoff lows, and deep tropopause folding events. The dynamical mechanisms described in the manuscript are therefore not entirely new in themselves.

What remains much less clear and what could constitute a substantial contribution of this paper, is the quantitative attribution of the observed ozone enhancements between direct stratospheric influence and in situ tropospheric photochemical production during the Mexico City episode. Given the current widespread availability of chemical transport models and online chemistry frameworks capable of separating these processes, I believe the manuscript would be significantly strengthened by including simulations performed with and without tropospheric photochemistry.

Such an analysis would provide a much clearer attribution of the ozone increases to STE processes and would allow the authors to quantify the extent to which stratospheric intrusions modulate urban ozone concentrations in a chemically active megacity environment. In my opinion, this additional analysis would move the paper from a largely qualitative dynamical interpretation toward a more robust mechanistic and quantitative contribution.

I am therefore inclined to request this additional analysis, as I believe it would substantially improve the manuscript and more convincingly demonstrate a genuine advance in our understanding of these episodes.