Dear authors,

Thank you for your detailed response. I have received additional minor comments from the reviewers, which I copied below. Once these comments are addressed, the manuscript will be suitable for publication in ACP.

Best,
Sally

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Reviewer 1:

I commend authors for such thorough and detailed revision that has addressed all my concerns. I recommend the manuscript for publication after few technical corrections, listed below, are maid:

Title: I do not think that ‘interannual increase’ is a correct term, ‘interannual variation’, maybe? Or, since you did provide a better proof for the trend, you could refer to an increase in secondary aerosol fraction due to potential growth in atmospheric oxidation potential, just a suggestion.

Reply to comment No 4: 'In Zurich, for instance, f44 during summer afternoons, when photochemical processes are most vigorous as indicated by high oxidant – OX (O3 + NO2), was found similar or lower than f44 on days with low -OX, while f43 (less oxidized fragment) tended to increase (Canonaco et al., 2015). The SOA is often divided into two factors: less-oxidized oxygenated OA (LO-OOA) and more-oxidized oxygenated OA (MO-OOA).'

Is this really correct – f44 lower for days with higher oxidation? Or this is a mistake, and the opposite was meant?

Reply to comment No 7: 'There are evident differences in meteorological variables from one period to the other (Fig. S7). In summer A, temperature (24.4º C) and solar radiation (259 W) are lower and average relative humidity (71%) and wind speed (2.0 m/s) are higher than in period B (27.0º C, 280W, 70.0%,1.7%), indicating a probably rainier or cloudier summer in period A.'

Check units for B, I assume, 1.7 is m/s? Also, are such differences in RH (70 and 71%) as well as WS (2 vs 1.7 m/s) significant? Otherwise, just state that they were similar.

Reply to comment No 7: 'The composition-dependent collection efficiency (CE) (Middlebrook et al., 2012) correction was applied (minimum, maximum) for Period A and B respectively: (0.45±0.68), (0.50, 0.99), exceeding CE=0.6 a 0.13% and a 1.5% of data).'

Is period B data missing here? I see the average, SD and range for the A period only?

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Reviewer 2:

The authors did remarkable work in revising their manuscript and taking care of the comments which were properly addressed. However, I still have some concerns regarding the conclusion which does not contain the main message of the work and appears poorly structured.

minor comments:
- The authors must reconsider the notation of their fitting parameters. Do they need to include 4 digits like lines 198-199 and Tab S1, while only 2 digits are used for the rest of the manuscript?
- Line 433: replace “hydro-carbon-like” with “hydrocarbon-like”
- Fig S3: The three different colors of grey are not easy to distinguish
- Figure S5: It would be better if all axes intercept at 0