The current paper investigates the occurrence and origin of plumes in the lee of major mountain peaks in the Himalayas. The authors combine satellite imagery from a few episodes with temperature and humidity data at a station close to Mt Everest. They conclude that most of the observed plumes are, indeed, cases of so-called banner clouds, meaning they have been generated by condensation of water vapor in an ascending air stream in the lee of the mountain (rather than just snow being blown off the summit).

The method to analyze the meteorological situation is straightforward: the authors compute the lifting condensation level (LCL) from temperature and moisture data at the observational site, and then check whether the LCL is below or above the summit of the respective mountain. If the LCL is below the summit, they hypothesize that one should expect a banner cloud to occur. Comparing this “expectation” with observations from satellite images indicates good agreement. This then allows the authors to conclude that the plumes observed on the satellite images are, indeed, real banner clouds.

This is the first study of its kind that I am aware of, and I think it is worth a publication in a science journal. My only criticism is that the spatial resolution of the satellite imagery is marginally low for the intended purpose: for me as a reader it required occasionally quite a bit of imagination to see what the authors see. Yet, the movies improve upon this issue, as the non-stationarity of (even a poorly resolved) feature in these movies allows one to more or less clearly identify the presence of a plume.

Below I have two major issues as well as a number of minor issues. My remarks are meant to help to produce a revised version.

Volkmar Wirth

Major issues:

I think it would be best to be explicit and honest about the low resolution of the satellite imagery. I.e, you best are honest and admit that the resolution is marginal, but (in particular in combination with the animations) just about sufficient to draw the conclusions that you want to draw. In your introduction you state that your results are “conclusive” (as opposed to earlier results); in my view this is somewhat overstated. To be sure, you add some circumstantial evidence, but this is not extremely convincing to me owing to the low resolution of the satellite imagery.

Also, I suggest that you systematically distinguish between the concept of a plume and the concept of a banner cloud. For me, a plume is anything that you see in the lee of a steep and high mountain (including snow blown off the mountain top). By contrast, a banner cloud is a plume that has been generated though condensation of moisture in an upwelling airstream in the immediate lee of the mountain.

Minor issues:

The movies: It would be good if you could provide movie-captions for all the movies.

Movie 1: it would be good to know how local time evolves as the movie passes by; is it possibly to include a little clock running with the movie accordingly? Or to give at least the time span (beginning and end time) covered by the movie.

The satellite movies are very coarse resolution. Is there a possibility to post-process them in order to more clearly focus on what you want to show? (Maybe not, indeed, because nothing beats the pattern recognition skills of the human brain.)

Table 1: I think it would be better to provide wind speed in m/s rather than knots.

Line 48: Sentence unclear to me.

Line 62: See our paper Prestel and Wirth (2016) where we elucidate the conditions under which one would expect a banner cloud to occur (steep mountain, week stratification).

Line 68: what resolution are these satellite images? Is it good enough to well resolve the cloud?

Line 79: which model? More details!

Line 82: “Hence….”: do you want to imply that banner clouds occur only on pyramid-shaped mountains?

Line 96: What do you mean by “initial composition” here? (It becomes clear somewhat later….). Can you exclude the possibility that these clouds are mixed-phase clouds?

Fig. 4: Make the Tephigrams larger, they are important!

Fig. 6: There seems to be a problem/mismatch between the yellow caption inside the image and the added caption below the image in the bottom row left and middle column.

Line 146 ff: I found it hard to verify the description/interpretation that you provide in the text when viewing the images.

Line 164: 4C? Do you mean 4 degrees Celsius?

Line 181/182: Haven’t you said something very similar a few lines earlier?

Line 204: What do you mean if you mention a “Jet stream….  embedded in a trough….”?

Figure 7: What do you want to clarify by showing this sequence of maps? Is the evolution important? Could you show just one panel as representative for the entire episode?

Figure 9: Apparently, upward is not northward in these satellite images. Please notify the reader in the figure caption accordingly. Also, it would be nice if you could somehow indicate the northward direction on these satellite images.

Line 228: Am I supposed to see that shadow in the satellite image?

Line 231/232: For me this is hard to see on the satellite image.

Line 244: The difference between sharp and fuzzy is hard for me to see on the satellite image.

Line 259: here you could specifically point to their Fig. 5b, which explicitly shows the diurnal cycle at Mt Zugspitze.

Line 290: “…. Presented evidence…”, well, rather weak evidence, essentially based on the interpretation of a very low-resolution satellite image.

Line 295: “… expect the plumes to form ….” not clear whether I understand the logic behind this argument.

References:

Prestel, I., and V. Wirth, 2016: What flow conditions are conducive to banner cloud formation? J. Atmos. Sci., 73, 2385–2402. 

The manuscript „The Mount Everest plume in Winter“ by E. E. Hindman and S. Lindstrom analyses the formation and composition of the Mount Everest plume. To do so, the authors examined two wintertime plumes in detail by using GMS images and atmospheric sounding data, which were used for an atmospheric model simulation. The results of this work conclude that the identified plumes are either composed of cloud droplets or ice particles, but were not composed of resuspended snow. 

The authors describe their analysis method very clearly and summarize the history of plume studies at Mount Everest in a very nice way. Their analysis method is simple, but was never done before for the Mount Everest plume. For this reason, I recommend to publish this work in ACP after a major revision.

Major comments:

1. This study is mainly based on satellite images with a very low resolution. For me as a reader, it was very hard to see the described observations on the images and especially the videos. I don’t doubt their method, but I think it is worth it to put some more effort in the presentation of the images and videos to make the authors’ statements more clear. I would recommend to add labels with time, km scale bars and markers for the location of the summits. 
2. The authors are focusing on the development process of the plumes and describe that the observed plumes and the Moore plume are not composed of resuspended snow. It gives the impression that plumes from resuspended snow are not possible at all, which I don’t think the authors intend. I think the Authors should make clear that this is just a case study over a few days (see Table 1) and plumes of resuspended snow might be still possible. I would also be interested in some more statistics. For example, how often do these plumes occur per month and how long do they usually persist? Also, the authors mention in the conclusions that the Everest plumes may be a source of snowfall. They didn’t mention that before in the manuscript. A rough estimation of how much the plumes contribute to the snow fall would benefit the manuscript. 
3. The authors mentioned the visible differences between resuspended snow and banner clouds (line 51), which were shown in Schween et al. (2007). I was wondering if this might be another indicator to support the analysis, if pictures from Mount Everest would be available. But according to line 65, continuous imaging is not available. I was wondering about that and found a video live stream (https://www.skylinewebcams.com/de/webcam/nepal/khumbu-pasanglhamu/khumjung/mount-everest.html ), which shows a view of Mount Everest from a similar position as in Figure 3. I think it would be possible to develop a simple program which takes snapshots of this stream and identify the plumes in addition to satellite images. Maybe that would help for a follow up study. 
4. The title is „The Mount Everest plume in winter“. If you would change it to „The formation and composition of the Mount Everest plume in Winter“ the reader would already have an idea what you are going to analyze. 

Minor comments:

Line 8: „plume often forms“…. How often? 

Line 10: „collect the corresponding meteorological data“… What kind of data?

Line 18: „is the highest elevation“ …. How high?

Fig. 2 to Fig. 8: All Figures need panel labels like „a) , b), c)“. That would make it much easier for the reader to find the panel. 

Line 88: „400mb“ and later in line 90 „300 mb“. A space between number and unit is correct. Try to be consistent through the manuscript. 

Line 99: „-35C“ … it is -35 °C. This needs to be changed in the whole manuscript. 

Figure 4 and 5: The profiles are too small and the resolution is too bad. It is not possible to identify the numbers. 

All Satellite images: It would be nice to have a km scale bar on the pictures to see the dimension. Same for the Videos.