Interactive comment on “Stratospheric observations of noctilucent clouds: a new approach in studying large-scale mesospheric dynamics”

observations of noctilucent clouds: a new approach in studying middle- and large-scale mesospheric dynamics".

Anonymous Referee #1 Received and published: 15 September 2019 Comment: This paper reports the stratospheric observations of noctilucent clouds from a balloon on 5-6 July 2018 near Moscow. Several hundreds of NLC images were taken for over one hour. Various NLC morphology and associated gravity waves are discussed in the paper, including ice voids, a medium scale GW. Overall, the paper is clearly written and the results are interesting. On the other hand, the English language needs to be tightened up. Please see the minor comments. Most importantly, the paper "oversells" itself. The significance is exaggerated. Except the factor of weather and doubled field of view, the balloon photographing of NLCs does not demonstrate a substantial difference from the ground photography. The PMC-Turbo experiment targets high resolution, unlike this experiment. Also unlike the authors claim, the spatial coverage of this experiment is not comparable to satellite observations.
Reply: As far as the PMC-Turbo experiment is concerned, we can note the following. This technique to image the PMC layer at scales from 100 km down to 1 m can be readily performed at the ground by using simple commercial digital cameras and telecentric lenses. Many images similar to PMC-Turbo ones have already been obtained from the ground. One can also use a small school telescope and camera attached to it to view an NLC layer at 1 cm spatial resolution and taking several images per second, if it is necessary. Nowadays it is very easy to obtain images similar to PMC-Turbo ones from the ground, and at much lower cost compared to any balloon-borne experiment. The advantages of using balloon-borne observations of NLCs are given below in the reply as well as in the conclusions of the present paper.

Comment:
Please correct these statements.
Detailed comments: 1. title: "large-scale mesospheric dynamics". Not really, the images shown cannot be used to study large scale waves, such as tides or planetary waves.

C2
Reply: We have corrected the title of the paper which now includes "middle-scales" since we observe both middle-scales (100-1000 km) and large-scales (1000-1500 km). Utilizing future long duration balloon flights (several days) one can study both tides and planetary waves. Since we discuss our future long duration flights as well, the title of the paper corresponds to the current and future state of the project.
Reply: These numbers are correct and kept unchanged.
Comment: 3. line 24: "unique", well, as shown in the next sentence, the field of view of a balloon borne camera is only twice of a ground observation (1450*750 km vs. 800*550 km).
Reply: Yes, the field of view of the present experiment was twice of the ground observation. We believe it is certainly enough to call this experiment "unique". We should also note that a field of view as viewed from a balloon can be significantly extended by using multiple cameras with wide-angle lenses (a project we are currently implementing) as well as observing NLC from higher altitudes (30-38 km). The present experiment was the first in this field and it will be upgraded in the near future. We keep the definition "unique" unchanged.
Reply: We have added the information on middle-and large-scale dynamics on lines 89 and 91 since we consider both middle-scales (100-1000 km) and large-scales (1000-1500 km) in the present study as follows: "In this paper, we report on scientific results of a new balloon-borne experiment dedicated to studies of NLC middle-and largescale dynamics at horizontal scales of more than 100 km (Dalin et al., 2019). Such experiment, conducted for the first time, opens new horizons for studies of middleand large-scale dynamical features in combination with a high spatial resolution at the summer mesopause. . ." We believe that the definition "opens new horizons" is valid for stratospheric observations of NLCs for 24 h and at large scales in case of a long duration balloon flight (several days) as we discuss in the present paper. We keep this definition unchanged in the revised manuscript. Comment: 16. line 166: is comparable to PMC observations"...This is a wrong statement. The space observation is much wider than the balloon one. Figure 3 clearly shows this.
Reply: Here we compare balloon-borne scales to scales of the PMC observation scene which has dimensions of 120 • x80 • , as measured from the nadir direction. This results in spatial coverage of approximately 2000 km along the AIM satellite track and 1000 C5 strate the advantages of a balloon-borne observation compared to a ground one. The conclusion e) clearly demonstrates its advantage to a space one. But it is important to realize that the combination of these points (24 h NLC observations both at middle/large and small scales) can only be achieved by using a balloon-borne observation. We have emphasized this combination at the beginning of the conclusions. We keep these conclusions unchanged in the revised manuscript.