## Summary

The authors propose a new method to estimate the bulk density and liquid fraction of falling snow and mixed-phase precipitation from collocated measurements of a micro rain radar (MRR) and a particle size and velocity (Parsivel) disdrometer. The method uses T-matrix simulations to retrieve the reflectivity factor (Z) from the Parsivel particle size distributions (PSD) assuming spherical precipitation particles with different combinations of ice an liquid water volume ratios. The simulated Z is compared with the observed Z from the MRR to constrain the possible solutions. The method is applied to two case studies and evaluated by comparing the derived bulk density with the reflectivity-weighted fall velocity (V_Z) from the MRR and the liquid-equivalent snowfall rate (SR) from a collocated precipitation gauge. The results show reasonable agreement between the derived and observed quantities, and are able to capture spatial and temporal variations of the bulk density across different sites and synoptic conditions.

The proposed bulk density retrieval method should be interesting and relevant to the ACP readers. However, I have some major concerns especially on the retrieval of bulk water fraction (v_w). My critical comments are presented below.

## General comments

Do the authors see a possibility that the retrieved high values of bulk density and liquid fraction during periods of low reflectivity and precipitation rate could be, at least partly, an artifact from applying the method on observations of very weak precipitation? The retrieval seems somewhat unstable in these conditions which is not surprising considering factors such as low signal to noise ratio due to weak signal. Yet, the authors draw considerable attention to the retrievals of these periods of very weak precipitation. It is worth considering which disciplines would benefit from the microphysical retrievals of weak mixed phase precipitation (<0.5mm/h)? I would suggest either introducing a threshold for minimum reflectivity or precipitation rate where the method is applied, or otherwise critically reviewing the method's performance in weak precipitation, where the precipitation rate falls below the sensitivity of the Pluvios.

I don't feel that the retrieval of v_w is adequately demonstrated in the case studies since there seem to be no time periods where there would be both a) agreement between derived and measured terminal velocity and b) notable precipitation intensity at the same time. It raises the concern how the method would perform in mixed phase situations with larger particles or higher precipitation rates. In my mind, the best way to address this would be to replace one of the case studies with another one that has significant intensity of wet snow, or discuss the possible limitations of the method's application.

In the presented case studies, it seems like non-zero v_w values only occur when bulk density is nearly saturated at over 0.9 g/cm. I'm concerned whether this is physically reasonable especially given the assumption of spherical particles. This raises the question whether, effectively, the liquid fraction would act as a kind of an overflow buffer in the calculations when density alone cannot explain the reflectivity values. This could rise from the assumption of maximum ice volume fraction (v_i). Or could it be explained with the drizzle-like nature of the precipitation during the v_w signals? This concern could be dispelled with a counter example.

The manuscript lacks discussion on the implications of assuming spherical particles. This might be significant consideration given the wide range of different particle habits and their shapes and preferred falling alignments.

Since the manuscript considers the liquid fraction, it would be worth showing or at least mentioning if melting layer signals were detected in the MRR observations.

The viewpoint in the manuscript is more technical and focuses less on microphysics. As such, the topic is suitable for ACP but might be even better suited for AMT. This is a possible consideration for resubmission after revisions.

The text is well organized and easy to follow. Relevant data and findings are visualized and given in tables. However, I noticed quite a few grammar errors especially with prepositions and articles, and therefore recommend some form of thorough language checking process for the manuscript.

## Specific comments

The title refers to snow density, but retrievals are attempted for snow, mixed phase precipitation and light drizzle. If liquid fraction plays an important role in the revised manuscript, it would be good to be reflected in the title.

The title indicates this is a preliminary study. Are the authors working on a more comprehensive analysis? Worth mentioning in the discussion.

L42: This sentence seems to suggest that riming and melting are the only processes affecting snow density. While these are important, one should not forget that, e.g., the primary particle habit and aggregation have great impact, too.

L59: As one of the selling points of the new density retrieval method is the use of robust intsruments that require little maintenance, perhaps it would be good to mention studies that use, e.g., PIP or Parsivel for density retrievals. Such studies could be found, for example, by doing citation analysis on Brandes et al. (2007) and Huang et al. (2010), as referred to in the manuscript.

Section 2: Details about the ambient temperature measurements are missing, in particular, the types of the instruments or sensors used. The temperature measurements, while not part of the main retrieval methods presented, should be of great interest for the reader as an indication for melting and other microphysical processes.

Section 2: I would like to see basic information about the Pluvios used such as make, orifice size and shielding.

L130: What is meant by a canting angle when referring to spherical particles?

L133: Why was this temperature range chosen for the simulations? Is it physically reasonable to simulate mixed-phase precipitation in -10 degrees Celsius, for example?

L147: I failed to find references to liquid water fraction from Huang et al. (2010). They seem to just assume particles to consist of ice and air. Either I missed it, or this reference could be more accurate.

L263: "The particle size was" to 'Maximum particle size ranged from'

L279: Since there are many sites involved in this study, it could be useful to have a small map showing their locations.

L315: "number density function" to 'number concentration'

L331: How is mean bulk density calculated here? Is it integrated over the total volume?

L334: Since rain was not excluded from the retrievals, we are now talking about the mean bulk density of mixed precipitation instead of snow. As the densities of rain and snow are quite different, the mean value is easily driven by the fraction of rain, masking the possible signal from snow properties.

L345: This sentence seems to suggest that the density of snow has an impact on the weather. It's unclear to me what was meant here. Please rephrase to clarify.

L526: "The ZHH variation with vw is much less than that with vi". I think, the opposite is true.

L560: What does the "shaded area" refer to in Fig. 5c?

Figures 5d, 9d-11d: There seem to be flat parts in the temperature measurements, where the measured value does not seem to change even for a fraction of a degree. These look like a measurement errors, perhaps gaps in the measurements. This raises concerns about the quality of the temperature measurements. The measurements should be checked and erroneous values omitted from the analysis. If there is a cause for concern about the quality of the measurements, it should be discussed in the manuscript.

Figure 6: The integration times in these figures are quite long. For example, in Fig. 6b, there seem to be multiple modes in the (D, v) distribution. Because of the long integration time, it is unclear if these modes are co-existing or if the dominating particle type is evolving over time. Have the authors considered analyzing the particle properties such as (D, v) distribution in shorter time intervals?

## Technical comments

The manuscript uses a mixed notation style for the symbols of quantities. Some are in italics, some are not, some use subscripts, some don't. I recommend more consistency in the style of these symbols. One could see the style guides of the publisher, if available, or other sources, for reference.

L10: Authors should choose between the spellings "disdrometer" and "distrometer". Currently, mixed spelling is used for this word in the manuscript.

L27: Since riming refers to a process and not a hydrometeor type, change "riming" to 'rimed particles'.

L73-74: The readability of this sentence could be improved by rephrasing.

L121: The authors probably meant 'modified FROM Huang et al. (2010)'.

L142: "as the increasing" to 'with increasing'

L178: "examined with" to 'compared with'

L186: "four with Pluvio" to 'four of them equipped with a Pluvio'

L196: "consistency of" to 'consistent'

L232: Full stop after "shown in Fig. 5"

L267: "relatively weaker" to 'weaker'. There are also other instances of using "relatively" with a comparative in the manuscript. I advice against this.

L274: "precipitation system" to 'precipitation'

L303: "has a more consistent relation" to 'is more consistent with the relation'

L345: "microphysics processes" to 'microphysical processes'

L353: "Consistency" to 'Inconsistency'

L361: The manuscript could be more consistent with how dates are written: with or without ordinal indicators.

L501: "blue lines" to 'blue', as there are also other symbols than lines.

L524: "DSD" to 'PSD'

L569: "derived" to 'shown'

Figure 5d: "MRM" to 'MRR' in the y-axis label.

Figure 6c: label (c) missing from figure

## References

References in this review follow the same notation as the reviewed manuscript.

Please see the attached review document.