Dear authors,
Thank you for submitting your revised manuscript, which has been reviewed by two referees. After the revision the manuscript reads much better. However, further improvement is necessary to meet the ACP quality requirements. Please take into account referee #2's comments in your next revision. In addition I also have many points for your consideration. Please submit your revised manuscript with your point-by-point responses to referee and editor comments.
Sincerely,
Xiaobin Xu

Co-editor comments:
(1) the English language needs to be polished further. There are many grammatical errors (e.g., incorrect use of "the", plural and singular, etc.). I strongly suggest that you either have the manuscript edited a native English-speaking expert or select the English language copy-editing.
(2) Line 25, I think you mean "Model results indicate that the study site is affected ‘differently’ by the surrounding areas in different seasons."
(3) Line 38, change "globally" to "global".
(4) Lines 44-45, "... photochemistry was identified as the dominant source of tropospheric ozone at some sites,". I think photochemistry is a dominant source of tropospheric ozone over all sites of the world, not only "some sites".
(5) Line 46, what do you mean by "largely uniform synoptic systems"? A synoptic system or a large scale weather system has its structure characterized by many parameters, pressure, winds, temperature, etc. The spatial distributions of these parameters are not necessarily uniform. I think it is better to change "largely uniform synoptic systems" to " synoptic systems".
(6) Lines 61-63, "The paucity of long-term surface ozone observations in the Tibetan Plateau, ... and can potentially lead to inaccurate simulation of surface ozone variation over the Tibetan Plateau". The accuracy of surface ozone simulation is determined by the capability of the model, the accuracy and fineness of emission inventory, the quality of meteorological data, etc., and should not be directionally influenced by the paucity of long-term surface ozone observations.
(7) Lines 70-71, I do not think this sentence should be placed here.
(8) Lines 74-75, it is better to move this sentence to line 49 (before "Due to...").
(9) Lines 78-80, check the language and logic of this sentence.
(10) Line 90, change "tourist" to "tourism".
(11) Line 104, was the radiation measurement system calibrated? Was it stable?
(12) Line 113, are you sure there was no obvious difference among the backward trajectories for 500 m, 1000 m and 1500 m? This is usually not the case. Please check again.
(13) Lines 139-140, what do you mean by "offset by 10 ppb"? Add 10 ppb to all hourly ozone value? Why can a normal distribution be obtained by doing so?
(14) Line 194, some of the data gaps in Figs. 4 and S5 seem to be over a month. Are you sure you have >56% of data for EACH month?
(15) What do you want to say with "the overall trends" here?
(16) Lines 212-214, Fig. 3 shows the daily minima in spring, summer and autumn are all at 8:00, contradicting to what you state here.
(17) Section 4, please mathematically show your regression model. Without this it is very difficult to understand your method and results.
(18) Lines 223-224, what do you actually mean with "For the boundary layer height quintiles were used"?
(19) Lines 239-240, the WRF-FLEXPART produced six transport clusters. Why did you only obtain one contribution?
(20) Lines 248-249, "and that these can lead to enhancements of surface of ozone of 150% of the hourly standard deviation". What result support this statement? I can see it nowhere.
(21) Lines 301-305, “This is probably due to the time delay between the maximum ozone concentration and the maximum solar radiation” (lines 302-303). What do you mean with this sentence? The fact is that there is a delay between both. “Hourly average SWD showed a positive correlation with hourly average surface ozone (correlation coefficient=0.77) which indicated that the potential of local ozone formation by photochemical production during the daytime contributed to the peak in the afternoon (Wang et al., 2006)”. It is too speculative and contradicting your points that are following. Local ozone formation may result in a good SWD-ozone correlation. However, a good SWD-ozone correlation may not necessarily be caused by local ozone formation. Wang et al. (2006) reported in situ photochemical production of ozone under the Waliguan spring and summer conditions that were very different from the Nam Co conditions. So, this citation does not support your speculation. I am not saying that there is no local formation of ozone at Nam Co. Theoretically local formation exists always where solar radiation is received. And ozone is also removed by local chemical and physical processes. If there is not net ozone production, you cannot attribute your SWD-ozone correlation to local ozone formation. Even if there is a net ozone production, you cannot simply do so with detailed analysis because the SWD-ozone correlation may be caused by some other mechanisms. In fact, you are saying that the wind speed and PBLH are the main factors (lines 305-306). I strongly suggest that you delete this speculation and keep consistency.
(22) Lines 345-346, “It is possible that the local NOx emissions in these two urban regions reduce the average ozone on the urban scale”. Again, this is groundless. NOx is the key precursor of ozone and promotes the photochemical production of ozone under favorable meteorological conditions. The meteorological conditions in Lhasa favor the ozone production as reported in Ran et al. (2014). Ozone at Dangxiong is controlled by large-scale physic-chemical processes, particularly the vertical mixing (Lin et al., 2015). Therefore, the differences between ozone values at Nam Co and those at Lhasa and Dangxiong should not be due to differences in NOx emissions and may be caused some other factors, such differences in altitude, meteorology, etc.
(23) Lines 388-389, “In the winter, no obvious region was identified, which was likely due to low surface ozone mixing ratios in all these areas.” Not clear.
(24) Line 393, “universal concern”?! Please do not use inflated language.
(25) Line 394, “varied” or “varying”?
(26) Line 404-406, “Its mountainous landform facilitates mountain-valley breezes and may sometimes pump up anthropogenic emissions especially during the winter (Xue et al., 2011)”. This is wrong! The impacts of anthropogenic emissions on the Waliguan station occur mainly in summer. And the Xue et al. (2011) paper is about a summer study.
(27) Lines 423-424, “The analysis suggests that stratospheric intrusions account for around 20% of the variability in surface ozone concentrations at Nam Co Station” is a misleading statement. Fig. 4 shows that stratospheric ozone makes at maximum a contribution of 20% to the variation of surface ozone at Nam Co. Most of the time, the stratospheric contribution is either zero or very low. I think you should state “…that the maximum contribution of stratospheric intrusions to surface ozone at Nam Co Station is about 20%” or give an average contribution.
(28) Please rewrite the third paragraph of Section 6 (Summary). This paragraph should be based on the major results in Section 5. I do not think this is the case in the current version.
(29) Line 466, “Our measurements provide a baseline of tropospheric ozone at a remote site in the Tibetan Plateau”. Be careful, your measurements of surface ozone at any site cannot provide a baseline (or whatever) of tropospheric ozone, which should be described by tropospheric column content and vertical distribution of ozone globally or over a region.
(30) Fig. 4, the “scaling factor” is not explained and not clear.
(31) Fig. 5, what are the red dots on the sub-plots? The location of Nam Co? If so, there are relative positions should not be varying.
(32) Fig. 10, the color selection of this figure is poor. Some of the trajectory clusters are hardly differentiated. I suggest that you use light grey for individual trajectories and well contrasted colors for the clusters.
(33) Fig. 12, the PSFC data look very strange. Why are the differences among season so large? See for example the difference between spring and winter? How did you obtain the weighted values? Were there calculated on a yearly or seasonal basis?
(34) Tables 2 and S1, it is not so straightforward what you are presenting in the tables. Please study the ACP instructions for the requirements on tables.