Please see attached PDF

I think the previous two reviewers had very nice summary and evaluation of the manuscript. I agree with a lot of their comments. Overall I think this is a very rigorous study of the IR based retrieval of cloud properties and it is worthy of publication. On the other hand I think the manuscript needs some modification and revision before it can be finally accepted for publication. 

First of all the manuscript reads more like a shortened Ph.D./MS. thesis than a scientific paper. It is way too long and hard to get insightful/meaningful results without having to go through many unnecessary parts. For example, the section 2 "physics background" should be significantly shortened if not removed completely as it is about something that is from textbook and well known. Similarly, I'm not sure if the Appendix A is needed either. In any case, I would suggest finding  all possible ways to make the paper succinct. 

The discussion of "disentangling the roles of cloud absorption and scattering" is interesting. However, it is based on the assumption that scattering is completely ignored in the IR cloud remote sensing, which is rarely the case in recent studies.  As mentioned by the first reviewer, a popular method is the so-called beta ratio method, which was first proposed Parol et al., 1991 and then improved and used in many follow up studies (e.g., Pavolonis 2010, Heidinger et al. 2010; Heidinger et al., 2015;). The beta ratio method is based on the so-called similarity principle that takes into account the strong forward scattering of cloud particles in radiative transfer.  I think it is important to point this out (with proper reference) and discuss it against Eq. (6). 

While the manuscript covers most of the important aspects of the IR based retrieval of cloud properties, an important missing is the impacts of cloud microphysics. A good paper on this topic is Zhang et al (2010).  I think it would make the study stronger if you can add some study/discussion to about this effect, perhaps along with the discussion on the effects of cloud geometrical thickness. 

Pavolonis, M. J., 2010: Advances in Extracting Cloud Composition Information from Spaceborne Infrared Radiances—A Robust Alternative to Brightness Temperatures. Part I: Theory. J. Appl. Meteor. Climatol., 49, 1992–2012,

Heidinger, A. K., M. J. Pavolonis, R. E. Holz, B. A. Baum, and S. Berthier (2010), Using CALIPSO to explore the sensitivity to cirrus height in the infrared observations from NPOESS/VIIRS and GOES-R/ABI, J. Geophys. Res., 115, D00H20, doi:10.1029/2009JD012152.

Heidinger, A.K.; Li, Y.; Baum, B.A.; Holz, R.E.; Platnick, S.; Yang, P. Retrieval of Cirrus Cloud Optical Depth under Day and Night Conditions from MODIS Collection 6 Cloud Property Data. Remote Sens. 2015, 7, 7257-7271. https://doi.org/10.3390/rs70607257

Zhang, Z., S. Platnick, P. Yang, A. K. Heidinger, and J. M. Comstock (2010), Effects of ice particle size vertical inhomogeneity on the passive remote sensing of ice clouds, J. Geophys. Res., 115, D17203, doi:10.1029/2010JD013835.