Dear Fan Mei et al.,
thanks for the revision of your manuscript.

As you know from the reviews the point of scientific significance of your manuscript has been controversely discussed. Since comparisons between performances of different instruments on different platforms (in this case the two research aircraft) are valuable for understanding benefits and limitations of the observations being made, thus being of interest to the scientific community, I decided to follow the suggestions of the reviewers that are in favour of publication of your manuscript.
However, please address the remaining reviewer comments (see below).

Best regards,
Wiebke Frey

Reviewer comments:
I commend the authors of this paper on making a number of improvements to the revised version of this paper. I really do think that comparisons such as this should be published and am pleased that the revised version of this paper has been resubmitted. I have rather few comments on the revision since the authors have done a good job of addressing my earlier concerns.

The only area that I feel has not been addressed is in answer to my original comment “What, if any ground comparisons were carried out and how useful these were to the overall performance of the instruments? Were data analysis approaches compared and what did these yield?”

I feel that though the authors now tell us what comparisons and calibrations were done they don’t tell us how useful they were at improving the overall performance. How variable were the calibrations from day to day? What happens if a calibration was not performed on a particular day could average calibrations be used or not? What is the degradation of performance? This is helpful information and some discussion of this would be useful.

Minor comments

Line 373: “exams” should be “examines”

The units of the quoted altitudes change from feet to metres, it would be useful if consistency was maintained throughout. Eg: lines 419 and 420, and elsewhere

Line 457-460 “criterion” and “criteria” singular and plural are used interchangeably

Line 463: are 4dp in the R2 justified?

Lines 467-468: “the challenging condition of airborne condition”

Line 491: different airmass(es)

Lines 500-502: “Above 3500 m, 500 the variations on the CPC and UHSAS measured concentration significantly smaller than the 501 variation at the lower altitude” needs a verb?

Line 621: use super and sub scripts

Line 722: no need for the apostrophe

Lines 727-728: “the Science engineering Associates” should be “Science Engineering Associates”

Line 729: “CDP had placed an 800-μm-diameter pinhole” should be “The CDP had an 800-μm-diameter pinhole placed”

Line 730: the FCDP….

Line 806-810: I am not sure that this is something that should be concluded in the way it is written. What is said is that there is around a 20% variation between two aircraft flying in essentially the same airmass due to spatial and temporal variability and as a result, modellers should use longer term data to constrain results. True, but realistically, large scale models require a greater degree of averaging than this for a range of other reasons.

Lines 911-912: This needs a rewrite, I am not clear what is being said.

Lines 915: aerosol “sample” flow variations

Lines 918-919: “Around 70% organic contribution maintains constant up to 3500 m, then decreases to 50%.” Change to “Around 70% of the AMS measured mass is organic and this fractional contribution is maintained from the surface to 3500 and decreases to 50% at higher altitudes.”

Line 920: “different mass resolution of the AMS instruments”

Dear Fan Mei et al.,

thanks for your revisions. Following up on these, I have a some more comments, see below.

Main comments:
1) With regard to the last reviewers comments about ground comparisons, I have the impression that you did not fully address the question. From how I understand your answer, comparisons to ground instrumentation had not been carried out, right? Why not? You refer to the ground site a number of times in your manuscript (e.g lines 31-33, lines 66-71, l 83/84, l 563-565, l 581-584) which makes me wonder why there was no comparison of ground based and airborne data. Such comparison might have given an even more comprehensive view on the reliability of the airborne data. Please also add a comment on the (missing?) comparison in the manuscript (and possibly a recommendation in the summary?).

2) Numbering:
There are several instances where I find the numbering does not follow the usual order. Starting with the numbering of author affiliations - the third affiliation that appears in the author list is number 13 and not, as I would expect, number 3.
Table S2 and S3 are mentioned in the manuscript before S1. Also some of the figures in the supplement are at higher numbers than others that get mentioned later.
So please check numbering of author affiliations, Figures, and Tables, also in the supplement.

3) Supplement:
The supplement reads as if the collection of sections/figures/tables was not always updated after an iteration of the review. Please treat the supplement with the same care as the main manuscript, keep in mind, that the supplement is published along with the final paper.
For some Sections of the supplement, I could not find references to it in the main manuscript. Either include references (e.g. to Section S1) in the main manuscript, or remove from the supplement. Actually, I could only find references to the flight on October 1 (without mentioning the exact position/section in the supplement), Table S2 and S3, and Figures S13 and S14.

Further comments:
l 115: trace gases concentrations -> trace gas concentrations

l 141: this comparson -> the comparison

l 242: number of small shattered particles (remove brackets)

l 269: developed by Weigel et al. (2016) -> move opening bracket

l 299: The other coordinated flight on October 1 is included in the supplemental document. -> Please include references to specific text/Section and Figures in supplement.

l 360/361: variation of the G1 altitude flight legs when the G1 flew around 50m/s higher...
Do you mean 'altitude' and 'higher' or 'flight speed' and 'faster'?
l 362/363: You argue that the G1 has a larger standard deviation in pressure due to the faster flight speed than normal - but HALO flew slower than normal (lines 304/305), would that no also be a possible source for increased errors in HALO observations?

l 374: Two regression results in Table 4 doesn't -> don't

l 377: Figure 4 - see comment 2)

l 385: chilled mirror hydrometer - hygrometer?

l 395: different saturations: How do you think will saturations impact on wind speed measurements?

l 447: The first criterion is the same criterion - maybe repeat it here with a few words.

l 454: Should the references in brackets be in the sentence? Move point back.

l 488: You sometimes say 'cloud-free flight' and sometimes you say the dates of the flights, please be consistent.

l 566: 0.17+-0.06 derived -> space missing

l 582: Figure 3, two aircraft -> both aircraft...

l 584: see comment 2)

l 636: You used a correction for coincidences on the FCDP data? In lines 596-598 you explicitly say that coincidence bias should not be considered for the cloud probe measurements to avoid deviations caused by application of different corrections!

l 701: This will lead to a considerable uncertainty ... -> add 'to'?
l 702-704: Can you elaborate why "especially for the regional or small scale modelling work"? For example, if someone does a modelling case study of a specific convective cloud, wouldn't more routine or long term measurements smear out the specifics/characteristics of that particular case study storm?

l 730: The UHSAS measurements ... (plural - two instruments being compared), same for CPC measurements.


Supplement:

Figures: Please move the Figures to the appropriate text within the Supplement, e.g. Figure 3 to Section S2 - CCN closure.

l 24: described by Mei et al. (2013b). -> brackets missing
l 24: CCN number concentration (typo)

l 26/27: Figures S3(a) and S3(b) (not Figure 3S...)

Figures S3 and S4: Please include 1:1 lines for guidance.

Section S3:
I have to admit, that I am highly skeptical about this section: Extrapolation of aerosol size distributions towards the smaller sizes should in my opinion not be done. The extrapolation is extremely uncertain, as you have to make assumptions about whether sources (particle formation events!) or sinks are present. As I cannot find a link to this section from the main manuscript, I suggest removing this section.

l 104: What is "AB, IE, and RIE"?

l 107-114: Sorry, but this part sounds like copy & paste from an email. Please keep in mind that the supplement will be part of the published manuscript and should be written like such. Please rephrase!

l 117: the inlet flow was kept constant -> keep tense as in the other sentences before/after.

l 134: (Molleker, S., in prep.) -> still in preparation or submitted in meantime?

Figures:
Please check for consistency in axis labelling (N, #/cc vs N, cm-3 for example), and for full axis labelling (some axes do not have labels at all).

S5-7: Occurrence not occurance, why Frequency and not Occurrence in Fig 6a?

S11: Would be better to plot similar to S3 (N vs N with altitude as colour code), including 1:1 line.

Table S2 and S3, cloud probes: In the manuscript you state that the G1 cloud probes were calibrated biweekly, in the supplement you write weekly calibration. For HALO cloud probes (e.g. the two CIPgs instruments) you state spinning disk calibrations before or after each flight, again, weekly calibration stated in the table. Please be consistent! What is the real frequency of calibration?

Dear Fan Mei et al.,
I found some remaining very minor issues in the supplement:

line 45: 'blew' -> below
line 50: missing white space: '(RIE)were'
line 76: You say G-1 here, but G1 elsewhere, please be consistent.
line 82: 'October 01' here, October 1 elsewhere, please be consistent.

Sections: Some Figure do not really belong to the sections they appear in, for example in Section 1 Figure S2-S5 are not related to 'Pilot preparation'. Maybe make the 'pilot preparation' part a subsection of a section that could be called something like 'Additional Observations'. Figures S11-S13 are not related to 'CCN closure' and could thus be in a new Section etc.

For final supplement: Please check that figure captions are not on another page than the respective figure itself!

Best wishes,
WIebke Frey