Review: Optical and microphysical properties… by Chazette and Raut

The authors describe a 24 h observation of clouds over Norway, from which 4 cases are selected and discussed. To me the interesting part is that we have an ice cloud probably at quite warm conditions.

The analysis and evaluation seem mostly correct and the paper is generally well written. However, I have some questions and remarks which I would like to have clarified prior to publication:

Page 7, line 3 I think you are referring to eq. 6 not 7

Page 9, line 16 to 18: if μi = 0 why is veff =1/3 (and not 1)?

Page 9, calculation of LR via Mie code: please state that this is only a (rough?) approximation as the ice crystals are not spherical.

Page 11, l16 “ice cloud formation highly probable” Please consider rewording. To my knowledge, in INP sparse regions supercooled liquid clouds dominate even at much lower temperatures. However, a recent paper that describes ice formation at temperatures slightly below 0C might be this

https://www.pnas.org/doi/pdf/10.1073/pnas.2021387118

Fig 3: I agree that we see a highly complex pattern. Hence, is this really a stratus cloud? The cloud at about 2km altitude from UT 18 to 23 probably yes.

Fig 3: Your VDR has a tendency to show high values above 6km, regardless whether a cloud is obvious in ABR or not. This may be a thin / subvisual cirrus. But what about a typical insecurity of VDR and ABR in about 6km altitude for the night 16 to 17 May?

Page 11, line 25: variability … due to wind shear. In the boundary layer I understand this point. What about the free troposphere? Maybe you could describe your measurement site a bit. E.g. are you surrounded by mountains? What was the synoptic situation / main wind direction etc.

… Ah, I see that you describe this in section 4.2. Still you may add a short description of your site and show this prior to the lidar results?

Page 15 line 30.:  relatively low depolarization values for Arctic cirrus have recently been found by Nakoudi. They speculate on a latitude dependence of depolarization. However, as your clouds are low and warm this may not be 1:1 comparable. Still I am not too surprised on your findings.

https://www.mdpi.com/2072-4292/13/22/4555

Table 1: eq 13 is the “backscatter weighted LR”. Eq 12 is a constant LR. If the LR according to eq. 13 is larger than for eq 12 this means (to me, maybe I am wrong) that the thicker parts of the clouds (high backscatter) have a higher LR and a large concentration (high beta) of smaller particles (your Fig 1.) I am wondering whether this does make sense. What do you think?

Fig 5: can you please state briefly how this has been calculated? This is the solution of the Raman channel for alpha, I assume. And beta was taken from Klett?  The lidar rations in Fig 5 are larger than in Table 1. Why?

Page 19, lines 6-10:  While everything (local pollution, Norwegian gas flaring, pollution from Russia and Canadian forest fires can occur), they will probably not manifest in the same night of observations. I would skip the speculation on the forest fires or Russian pollution unless you have a clear hint that you have seen it in the lidar data. Instead, you see an ice cloud at warm conditions. Maybe the growth rate is simply slower?

Find my review in the attached PDF.