This manuscript presents a valuable study of surface ozone variability over the Tibetan Plateau using in situ observations from Nam Co (NMC) and Nepal Climate Observatory-Pyramid (PYR), together with EMAC tagging simulations. The study investigates the seasonal and daily variability of surface ozone and attributes it to three broad source regions: the Northern Hemisphere and Tropical Stratospheric Source (NTST), the Northern Hemisphere Mid-High Latitude Tropospheric Source (NHTS), and the Tropical Tropospheric Source (TRTS). The results show that stratospheric influence is strongest in spring, that NHTS transport plays an important role in summer, and that TRTS exerts a particularly strong influence during the pre-monsoon period, especially over the southern and central Tibetan Plateau.

Overall, I find this to be an interesting manuscript that fits well within ACP. The topic is important, the combination of observations and tagged model simulations is appropriate, and the physical interpretation is generally robust. The manuscript is also well organized, and the figures are clear. I therefore think it is suitable for publication after moderate revision.

General comment

1) My main concern is how to address the relatively large model bias at the PYR station. A mean positive bias of 12.6 ppbv is reported for PYR in the EMAC simulation, which is much larger than that at NMC. This may affect the source-attribution results discussed in Section 4. The authors should clarify which source components may be most strongly overestimated at PYR, for example, NTST, NHTS, and/or TRTS. One possible way to address this issue is to estimate simple scaling factors for NTST, NHTS, and TRTS that reduce the mean model bias while also improving the correlation coefficient and/or minimizing RMSE. Applying such scaling factors could provide more robust estimates of the relative source contributions. I therefore strongly encourage the authors to make an effort to correct or at least better constrain the PYR bias.

Specific comments

2) Page 6, line 18

A nearby grid cell is used for the model comparison at PYR. Please clarify the differences among the nearby candidate grid cells, and discuss how these differences compare with the reported bias of 12.6 ppbv.

3) Page 11, lines 15–17

For the pre-monsoon, monsoon, and post-monsoon periods, please specify the exact date ranges.

4) Page 11, Table 2

Since the tropospheric sources are analyzed by season in Section 5.2, I suggest that Table 2 also include tropospheric mean values averaged by season for consistency.

5) Some grammar edits

Page 14, line 9: “This background also helps …”

Page 25, line 5: change to “this study systematically reveals …” for consistency with the tone used in the Conclusions

Page 25, line 13: “this study has analyzed …”