The reviewer has indicated the manuscript is substantially improved. Please pay close attention to the requested changes in making the next round of revisions.

The authors have addressed all comments. At this point, there is only minor editorial work remaining, as follows.

Throughout manuscript: change “foot” of the mountain with “base” and re-assess the use of “due to” throughout the manuscript.


P2L2-3: remove the “i.e.,” before the site names – not needed.

P2L15: Revise the following sentence “On the other hand, alkyl nitrates at TMS were...” to something like the following:
”In contrast to TW, the alkyl nitrate levels measured at TMS mainly resulted from the photo- oxidation of the parent hydrocarbons at TW during mesoscale circulation, i.e., valley breezes, corresponding to 52-86% of the alkyl nitrate levels at TMS.”

P3L2: change “due to” to “because of”


P3L6: change “due to” to something like “resulting from”


P5L18: delete “i.e.,” not needed – add comma after (TMS)


P5L28: You state that the monitoring site was 15-20 m above the ground – that’s a pretty significant range. Is there more concise information either about the station/inlet height to narrow down this range?

P8L1: Please introduce CO, NO, NO2 and NOx – this is the first time these have been presented in the manuscript.

P8L6: “baseline” should be change to “background”


P8L10-16: The following sentence is confusing – first off how often were each of the different analyzers calibrated? Regarding the “other” analyzers, it says they were calibrated “daily” using scrubbed ambient air – this would be zeroed, not calibrated. The way this is written, the “other” analyzers are only calibrated weekly, but zeroed daily, and we are not provided the information on the temporal calibrations of the ozone analyzer. Please revise to state the frequency of the zeros and calibrations for each of the instruments.
The O3 analyzer was calibrated (how often, hourly, daily, weekly?) by using a transfer standard (Thermo Environmental Instruments (TEI) 49PS), while the other analyzers were calibrated daily by analyzing scrubbed ambient air (this is zeroing the analyzer) (TEI, Model 111) and a span gas mixture weekly with a NIST (National Institute of Standards and Technology) traceable standard which was diluted to representative mixing ratios using a dynamic calibrator (Environics, Inc., Model 15 6100).


P9L17: It’s hard to tell in the pdf version, but this should be the beginning of a new paragraph.

P12 Table 1 (and also S1): it would be useful to either include 10th and 90th percentiles or quartiles (or both) to the statistics – this allows the reader to better assess the variability in the data and between sites.

P13L19-21: Revise to the following:
High mixing ratios of O3 and alkyl nitrates were usually associated with meteorological conditions with high-pressure system and/or stable conditions, such as high temperatures, intense solar radiation and low wind speeds.


P13L27: delete “well”
The maximum values were comparable and the diurnal patterns well tracked each...

P14L1: add “the”
other for the C3-C4 alkyl nitrates...

P14L5: delete “respectively”

P14L6: simply say “high O3 days” so the sentence reads more fluidly (not high-level)


P14L19: States that the elevated levels of MeONO2 and EtONO2 are “likely indicative of photo-oxidation of methane and ethane”. Please provide an estimate on this point as the lifetime of methane and ethane are sufficiently long that local production usually isn’t dominate for these two gases.

P14L26: Revise this to say that “...the high levels of MeONO2 and EtONO2 are likely related to marine...”

P16L6: replace “helpful” with “valuable”


P16L21: Introduce Eq. 1 – currently, it simply resides in the text with no reference to it.


P16L26: revise to “...processing, respectively; [OH] is the...”


P17L8: delete “most”


P17L17: Delete “[OH]”: The diurnal average OH mixing ratios [OH] were


P17,L20: Revise to: “...because the other parameters (kA, kB, α1, α2 and JRONO2) were obtained from the literatures...” Note: literature should not be plural.


P19L13-18: First, the following should be revised: “...due to long atmospheric lifetimes and slow photochemical degradation rates of methane and ethane...” to something as:
“...resulting from their relatively long atmospheric lifetimes and the slow photochemical reaction rates of methane and ethane...”
Moreover, this goes back to P14L19, which suggested that the elevated MeONO2 and EtONO2 are a result of photochemistry – these sections can be construed as contradictory. Please reconcile the discussion on P14 by including a calculation or revising the text accordingly.


P20,L3: Change to “Regarding the C3 alkyl nitrates,...”


P20L5: “revealing” isn’t a great word choice in this case. Recommend changing to something like: indicating, demonstrating, etc.


P25L25-26: Revise to: “The standard error in Figure 7 were...” Note: error should not be plural.


P21L26-29: Revise the following: Since the air masses arriving at TMS were photochemically aged (Guo et al., 2013a), the original source profiles of alkyl nitrates and their parent hydrocarbons were altered at this mountain site.” to something like:
“The source profiles of the alkyl nitrates and their parent hydrocarbons were altered resulting from photochemical transformation during transport to the TMS site.”


P22L2, 8 & 15: change n/i-butane to i/n-butane to be consistent throughout the manuscript.

P24L16: As written, this refers to a single forest fire – is this correct or should this be plural?

P26L1: Delete “Instead” and start the sentence with “The C3-C4...” or say something such as: “In contrast to the C1 and C2 alkyl nitrates,...”

P26L8: Replace “brought” with “transported”


P26L22-23: for the following: “...photochemical formation of alkyl nitrates was occurring, and eventually contributed to the ambient levels of alkyl nitrates at TMS.” either delete the part of the sentence after the comma or revise as follows: “...photochemical formation of alkyl nitrates was occurring, contributing to their ambient levels at TMS.”


P27L4-8: For the following:
The results demonstrated that when there was mesocale circulation, the levels of alkyl nitrates at TMS were dominated by the photo-oxidation of their parenet hydrocarbons originated from the urban site TW, one possible reason leading to similar levels of alkyl nitrates at the two sites, though the values of their parent hydrocarbons were lower at TMS.
Revise to something like:
These results demonstrate that when there was mesocale circulation, the alkyl nitrate levels at TMS were dominated by the photo-oxidation of their parenet hydrocarbons that originated from the urban site TW. Although the mixing ratios of the parent hydrocarbons were lower at TMS, this is still one possible explanation leading to the similar levels of alkyl nitrates measured at the two sites.


P27,L24: change to “...alkyl nitrates measured at TMS.”


P27L26: change “...in the...” to “...for the...”


P28,L20-21: For the following: In addition, as the formation of alkyl nitrates consumes NO, it resulted in negative contribution to O3 formation.

Change to: Additionally, as the formation of alkyl nitrates consumes NO, this process results in a negative contribution to O3 formation.

P29L20: Change: “The results...” to “These results...”


P30L19: change “...led to the...” to “...resulted in...”

Figure S1: Change to sans serif font and adjust the colors so TW is red to be consistent with the rest of the manuscript.


Figure S2: Is it possible to increase the clarity of the labels on the weather charts?