The paper by Harm-Altstädter et al. addresses an important topic of small-scale aerosol distribution and dynamics affected by different atmospheric boundary layer (ABL) properties. The study, which focused on the transport and mixing of ultrafine aerosol particles (UFPs) as possible sources of new particle formation (NPFs), was performed by combining measurements of unmanned aerial systems (UAS) with continuous observations from the ground at different altitudes, at the observatories of Gruvebadet (67 m asl) and Mount Zeppelin (472 m asl). I believe that the topic is interesting and there are elements of innovation especially because the aerosol distribution is not frequently studied with these approaches. The paper is written and developed very well and should be suitable for publication after providing a better context and clarifying few details.

General comments:

The manuscript is unnecessarily long in some parts (1 Introduction, and 2 Description of the measurement site, instrumentation, and data availability) and various pieces of information are repeated several times throughout the text. These risks making the manuscript difficult to read and boring in parts.

I recommend the authors to reduce sections 2.3.1 and combine sections 2.3.1 and 2.3.2 in section 2.3.

The captions are very long, can’t you take some information to the text? This applies for all long figure captions (Figure 1; Figure 2; Figure 3; Figure 5; Figure 7; Figure 9; Figure 10). The same for Table1.

Specific comments:

• L153: Further?
• L153-155: would move this sentence after L162.
• L156: where eBC mass concentration were collected?
• L221: what kind of meteorological measurements? Please, specify the parameters.
• L243: Fig. 3b and Fig. 4b (and throughout section 2.4)? I only see Fig. 3 and Fig. 4.
• Figure 3 and Figure 4 show different time scale, daily and every two days. Please uniform them.
• Figure 5 and Figure 6 are very complex and difficult to follow.
• Section 2.4 is a bit confusing; it is not clear which days and which types of measures are available. Considering the short duration of the measurement campaign, it would perhaps be clearer to modify Table 1 by providing an overview of all days and data available (not only of US ALADINA).
• L263-265: I’d move this sentence to the beginning of the section 2.4, where the authors provide the general overview (Table 1).
• L324: period and not colon.
• L 536: the authors write that the frequency of occurrence of NPF events during the ALADINA period was 22% while in the abstract, L8-9, they write “A high frequency of occurrence of NPF was observed, namely on 55 % of the airborne measurement days”. Please explain.
• L 534-544: I recommend moving this sentence somewhere in Discussion. Also, where is it mentioned about GR in the paper?

The current paper is outstanding on the quality of the science and the data collection and interpretation. However, I am afraid the presentation is very poor. In a paper, it is important not only to collect the data - but also to present them well.

I suggest two main improvment that are really necessary for this paper to be published. Failing to address this, this paper cannot be accepted.

1) The paper is too diluted, the reading is heavy and at the end one cannot find the major information. Please consider some bullet points at the end of the discussion with 5 major sentences stressing the major findings

2) Figures. The figures need all redrawing, they are not clear and some mirror images are impossible to look at. figure 5 and 6 are not pubblishable, please consider putting it all in 2d normal smps plotting with site a and site b below and above, with the vertical profiles in the middle, and simply state on the left chart what is what. (like figure A1 and A2 that are clear and simple)

figure 11 and figure 12 are interesting, what is the brown in the sea, river influnce or ice? if ice put it in white or blue, it may help the reader to see what you are doing.