Summary

In their manuscript "Assessment and application of melting layer simulations for spaceborne radars within the RTTOV-SCATT v13.1 model", Mangla et al. briefly introduce the radar simulator recently implemented in the widely known and used radiative transfer model RTTOV v13.1. In addition, they present a revised version of the melting layer model by Bauer (2001). The new radar simulator and the melting layer model are validated and applied in a case study for a single location and time step over the Atlantic Ocean and in a statistical approach to observations of GPM/DPR in different climatic regions. The RTTOV radar simulator is used with the ARPEGE global NWP model as atmospheric input.

The results show that the radar simulator, in combination with the new melting scheme, is able to realistically reproduce the reflectivities even in and below the melting layer for the case study at Ku- and Ka-band in comparison to GPM/DPR observations. For the statistical comparison, they show a significant improvement in terms of first-guess departures of the simulation from the observations.

Scientific contribution and general comments

The radar simulator in RTTOV is a very important extension and makes the model even more usable for the community. Having a bright-band scheme included in the model is very good as well. Therefore, the manuscript gives a substantial contribution to the scientific progress. 

Technically, I would have appreciated an additional proofreading, maybe even by a native speaker, before submitting the manuscript to AMT for discussion. Some parts or sentences are not very easy to read. In addition, there are many inconsistencies: 

• the use of commas before and in enumerations
• whether bright-band is written "bright-band" or "bright band"
• same for Ku- and Ka-band
• using in units in situations like "15 dBZ and 10 dBZ" or "15 and 10 dBZ"
• acronyms they are sometimes introduced like "Global Precipitation Mission (GPM)" and sometimes "global precipitation mission (GPM)"

In the specific comments, I'm not mentioning all typos and, in my opinion, falsely set commas.

Specific comments

p.1 l.4: TOVS is not explained here

p.1 l.9: GPM  is not explained here

p.2 l.24: CloudSat should be written with capital S throughout the manuscript

p.2 l.45-47: The sentence should be rewritten to "In the melting layer, the maximum size snowflakes are first transformed into wet flakes and then to raindrops of smaller sizes of equivalent mass and less number density as compared to the original flakes (Galligani et al., 2013).". Thereby, I'm not sure about "less number density". Why should that change? You do not change the number of particles within the volume.

p.3 l.63: change "retains" to "retain". Geer and Bardo are two people.

p.3 l.79: Why are graupel and hail written capitals? Same later on in the manuscript.

p.3 l.87: "whether if" remove "if" p.6 l.139: Remove "." in "mm⁶.m^-3"

p.6 l.149: "radar range gate"

p.7 l.181: "The Marshall and Palmer (1948)(hereafter MP)" what?

p.8 Table1: Remove "s" from hydrometeors

p.9 l.223: "density and mass ... are"

p.9 l.226: "...melted hydrometeor fraction f_m..."

p.9 l.231: "...has also been used..."

p.10 l.243: "...melting layer model" or "scheme"

p.12/13 figure 3/4: Why do the lines at different temperatures cross without following any rules.

p.20 l.345pp: "this can.." and "This can..."

p.21 l.361/362: I do not understand this sentence.

p.22 figure 9: "...less (larger)..." less and larger do not belong together. It is either "less and more" or "smaller and larger"  

p.24 l.384: There is always a profile of DFR. Sometimes the values are just equal 0.

p.25: First define V1 and V2 before talking about them.

p.25 l.405: "(given in the methodology diagram)" Please mention the threshold values here.

p.26 l.418: Mention here what the markers I, II, and III denote.

p.26 l.426/427: This sentence needs to be revised by including some articles.

p.27 figure 12: labels on the colorbar need to be adjusted better

p.29 l.449: I do not see the bright-band peak in the observations

p.29: In line 133 you mention the averaging of the profiles and promise to discuss it later. I would have expected this here.

p.36 l.487: Please give a reference where the melting layer scheme is validated for the passive simulations.

p.38 l.544: Why are there only five temperature bins but n_levels level?

Please see the attached PDF