Thank you for your extensive efforts to re-structure the manuscript and revise for review comments/concerns. We are moving to accept the manuscript, but there a number of requests prior to that:
(1) There are a wide number of sources of light alkanes that could contribute to enhancements downwind of an urban area. If you are going to attribute the enhancements as “likely” specifically from petroleum processing-related facilities, it would be necessary to clearly point to where the enhancements were high in WAS samples with back trajectories to a site AND show how the relative ratios of light alkanes from these sources match the chemical source profile expected for petroleum operations (which are varied depending on facility type and feedstock composition). I worry your conclusion “Ethane, propane, n-butane and cyclopentane, exhibit the highest average concentrations across all three flights and can likely be similarly attributed to petrochemical refining and natural gas processing”, which also appears in the results section is attributing the enhancement entirely to that source sector (since past studies had a similar conclusion). These efforts should be taken to substantiate this claim, or you can restructure your conclusions (in both locations) as a suggestions or hypothesis.
(2) This conclusion is unclear to me ”They also provide clear evidence that relatively small local sources can still play a significant role in air pollution in a megacity region.” I think I understand the point you are trying to make, but the statement formulation of “relatively small” and “significant role” are contradictory as stated. Are they small in footprint? Source activity? Right now it reads as if the emissions are small.
(3) It would seem to me like the term “sorties” (appears twice) is not most appropriate here, and is likely to confuse readers.
(4) “CPC is often used to indicate particle number concentrations in figures and tables, e.g. “CPC Counting” in Figure 8. Please call this particle number concentration (Simialr for panel titles and axis titles in Figures 4-6) and in Table 3, it would be better to just label to “PM” rather than “CPC”
(5) In my review of your changes, I found a number of errors/typos. Please proofread the text and figures one final time before re-submission. Here are 2 examples (that would not be caught by copy-editors):
a. Figures 10 and 12 list “npentane” in the legend, as opposed to “n-pentane”
b. Both those captions state that altitude is on the x-axis, it is in fact on the y-axis