Dear authors,

Reviewer #2 has some additional comments on your manuscript that you should address (see below). They mostly concern the structure of the paper.
After this revision is carried out satisfactorily, I will be happy to accept your paper for publication in ACP.
Best regards
Barbara

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Comments by Reviewer #2

Suggestions for revision or reasons for rejection (will be published if the paper is accepted for final publication)
Taylor et al. present a thorough and comprehensive analysis of measurements from the COPE field campaign. The large dataset enables the authors to draw several conclusions regarding the coastal versus inland and flight-to-flight variability of aerosol in terms of chemistry, size, and cloud nucleating abilities. Although the manuscript has improved from its original version, I find it somewhat difficult to follow due to the level of density of the measurements. It is a difficult task to eloquently discuss such a vast set of observations, but with some restructuring, the story would flow much better. The science is sound and the data needed are already presented, but I recommend some minor revision of the structure prior to publication in its final form.

I suggest the authors consider limiting the first several sections following the methods to simply and concisely stating the results, followed by a discussion section linking the different yet complementary measurements for each flight, then how and why these vary between the flights. As it stands, the discussion jumps back and forth between different flights and measurements, which renders it difficult to follow. The synergy between the different measurements is unique and interesting, for instance the authors do this for the correlation plots between CCN and various aerosol observations (Fig 9). The discussion corresponding to this figure is convincing and a great example of what could be conducted for all the analyses to make the combination of the measurements stronger. As an example, the authors could directly explain how the size distributions can be explained by the chemistry and meteorology. Analysis such as those presented in Fig 9 are the heart of the paper and demonstrate the dependence of aerosol climate effects on aerosol properties.

If this restructuring is done, I would also suggest reordering so the results for size are provided prior to the chemistry, then, as the authors currently have, finish with the aerosol climate related measurements/parameterizations.

This would also alleviate issues with discussing results before they are introduced, e.g., on page 12, lines 22 and 32 (CCN and PBAP not yet shown) and page 13, line 5 (CCN again).

General comments:

The authors state that Rosemount inlets were used for the internal instrumentation. What are the specs on these inlets? Was there not a main inlet to the aircraft (i.e., isokinetic or CVI)? If a non-CVI inlet was used, how did the authors filter out interference from very small cloud droplets in the overlap region of the PCASP and CDP size ranges? This at least should not be an issue for the CDP considering the particles need a relatively substantial amount of water for the CDP to detect them.

Could the authors conclude that 05 and 18 Jul were more polluted based on the fact they had the most stagnant winds (i.e., less clean out and more opportunity to enable gas phase partitioning/particle aging)?

Although the WIBS observations are interesting, because they are only discussed briefly, they seem superfluous in the context of the aircraft measurements. How representative are the ground-based observations for what is aloft? Comparing ground-based aerosol and aircraft-based cloud properties is somewhat of a stretch, unless the authors clearly state this potential source for inconsistency. Further, the entire focus of the paper is on the aircraft measurements. If the authors choose to keep the WIBS measurements, there are other ground-based aerosol observations that could be used to support their findings from COPE (Leon et al. 2015). More of an emphasis on ground-based observations would balance the story nicely. However, this may also increase the length of the paper and hinder the focus.

Specific comments:

Page 2, line 1: Lower than what?

Page 4, line 17: Briefly elaborate on “active drying”.

Page 4, line 23: The chloride ion is traditionally designated as Cl-.

Section 2.2: It is stated later in the text that the description of the WIBS is provided, yet not a whole lot of details on the WIBS here.

Page 8, lines 6-10: Provide a sentence or two on why it is important to look at sulfate neutralization.

Page 11, line 14: How exactly was this done? SMPS and PCASP measure electric mobility and optical diameters, respectively. Shouldn’t a conversion be done in this case to permit combining the distributions? Along these lines, it is difficult to see the dashed versus solid lines for the respective instruments in the figure.

Section 3.3: At times, it is difficult to ascertain if the authors are talking about the coastal, inland, or both size distributions. Please clarify throughout when drawing conclusions.

Section 3.4.2: This section also contains sizing observation; the section title is not entirely inclusive. This would be alleviated if the R&D section was restructured and separated.

Fig 10: This figure is somewhat distracting and draws away from the more exciting results. The authors could eliminate this figure and simply state that none of the parameters in Fig 9 correlated well at 0.9%.

Fig 11: How were lower ice concentrations observed during updrafts than downdrafts? Sullivan et al. (2016) demonstrated how vertical updrafts are a key element to cloud ice formation (can explain up to 48% and 89% of ice crystal number). Also, I am assuming these are number concentrations, and if so, relabel the axis to calculated INP or ice crystal concentration.

Sullivan, S.C., Lee, D., Oreopoulos, L., and Nenes, A (2016) The role of updraft velocity in temporal variability of cloud hydrometeor number, Proc. Nat. Acad. Sci., in press.