General Comment

This study investigated raindrop size distribution (DSD) characteristics of precipitation cells observed by a polarimetric radar and ground-based disdrometer data using three-year datasets and environmental factor that can impact the DSD characteristics. The analysis method is adequate, and the figures are clean and easy to see. However, I am concerned with the sample size used in this study. I think that the data period (3 years) is good and enough to collect samples. However, the sampled cases shown in Figs. 7-9 were very small, and the correlation coefficients were very small. Therefore, I cannot be convinced with the impacts of the environmental factors discussed using Figs. 7-9. Moreover, the title says “… eastern Japan,” however, the radar data used in this study are from one radar at one location, and the disdrometer data are also from one location. I am not sure if this dataset is enough to represent the characteristics in “eastern Japan.” It is also unclear in the manuscript what types of precipitation cases were focused and why this study focused on equilibrium shape of DSD. Definitions of cells are not clear. Details are listed below. The author should address those or perhaps needs additional analyses before publication.

Specific comments

1. Title: As I mentioned above, the title says “… eastern Japan,” so I expected this study used large datasets from multiple locations in the eastern Japan. However, the radar data used in this study are from one radar at one location, and the disdrometer data are also from one location. I am not sure which area in Japan is represented by “eastern Japan” and if this dataset is enough to represent the characteristics in “eastern Japan.”

2. Introduction: It is unclear in the manuscript what types of precipitation cases were focused in this study. I supposed that the author was interested in heavy rainfall, but I am not sure why this study focused on equilibrium shape of DSD. The instruction mentioned multimodality in DSD shapes, but the mainstream of this study did not account for the multimodality (I think).

3. Definitions: Definitions of cells and target cases are unclear. Methods of tracking cells are also unclear. I have the following specific questions.

• 1) What type of precipitation cells targeted is not clear. The sampled period included all seasons in 3 years. Did the study target any types of precipitation, including monsoon, MCSs, isolated, embedded, Baiu, snow, and etc.? If so, what type did have most cells? It would be great if the author provided the numbers sampled for each precipitation type.
• 2) Lines 142-143: I am not sure what cell life stages were targeted by using the lambda values. Could the lambda values capture from the cell initiation through the cell decay? What radar reflectivity or rainfall rate values corresponded to those lambda values? Were the lambda cells in Fig. 1 consistent with reflectivity cells?
• 3) How did the radar data cover the 3D volume? What is the maximum height? The radar PPI volume scans cannot see higher altitudes near by the radar. What is the height limitation? Were vertical structures retrieved from all cells without the impact of this limitation?
• 4) Section 2.2: Please provide the domain.
• 5) It was unclear for me that it was tracked in 2D or 3D. If 3D, I have the similar question to. 3). Was the tracking impacted by the radar data limitation at higher angles?
• 6) Line 153: “the maximum of each slope is defined as highest”: I cannot follow this. Does each slope have multiple slope values? I cannot understand.
• 7) Lines 156-157: This sentence does not make sense to me. CAPPI data is available every 5 min. What does “before and after 1 hour of CAPPI” mean?
• 8) Table 1: What is the difference between feature and cell? What is the difference between event and cell?
• 9) Lifetime: Similar question to #3-2). What life stages were captured? Can it capture cell initiation, beginning of precipitation, beginning of cloud formation, just life stages of heavy rainfall, or time with raindrops >1 mm?
• 10) How did you calculate the volume and area? How did you define the volume/area? Did you use the lambda values?
• 11) Line 212: Similar question to #3-2). What life stage corresponds to the first detection?
• 12) Line 217: Why 2 km?
• 13) How did you decide the inside and outside features of the convective clouds. How did you define the convective cell boundary?
• 14) Line 228: How did you define the volume?

4. The sample size (tracked cells) seems to be enough to me in Table 1 and Figures 2 and 3. However, the samples shown in Figures 7-9 are very small (30-40 points only). Why? Moreover, the correlations are small. All discussions about the environmental factors were based on those plots with very small correlations. Therefore, I cannot be convinced with the impacts of the environmental factors discussed using Figs. 7-9. I have the following specific comments:

• 1) Lines 243-244: I cannot see this in the figure. It looks to me that D0 and lambda are scattered widely, too. Perhaps, did you mention the correlation coefficient values?
• 2) Lines 250-251: It is difficult to see this… Figure 7a and 7b both showed positive correlation coefficient values. Could you revise the sentence?
• 3) Line 251 “D_0 is negatively…”: This does not make sense to me. Fig. 6 shows that LWC increases when D0 increase. I suppose that LWC can increase when PW increase, so D0 increases when PW increases. Why D0 has negative correlation with PW?
• 4) Lines 254-255: This cannot make sense to me, too. Why does the large amount of water vapor contribute to the high concentration of raindrops? What is the mechanism? Is there an aerosol effect?
• 5) Line 263 “These results…”: I cannot see this in Fig. 9.
• 6) Figs. 7-9: Correlation coefficients are very low for all relations in those figures. Absolute values for all correlation coefficients are less than 0.4 (weak correlation), except Fig.8b. The discussions about the relationships between DSD parameters and environmental factors are based on such low correlations. Moreover, the number of samples for each plot is small (<50). I do not think that the small numbers of samples can represent general characteristics of convective cells in eastern Japan.

5. Environmental factors

The environmental factors discussed are limited. CAPR, KI, PW, wind shear, and TLR could be major factors, but other factors should also be discussed, such as humidity (low level/mid levels), aerosols, seasons, etc. As I mentioned above, the correlations shown in Figs. 7-9 are very low. I would suspect that there could be other factors that can better correlate with the DSD parameters.

6. Others:

• 1) Lines 238-239: Was this also associated with cell’s shape and where is the “center” of the cell?
• 2) Lines 293-295: Was there a size sorting effect for the horizontal distributions?
• 3) Lines 309-310: This also does not make sense to me. Please explain the mechanisms why weaker vertical wind shear contributed to a high number concentration.
• 4) Lines 313-314: Why was the change in Nw larger with increasing rainfall amount under the humid environment? “change” is an unclear word. Do you mean increase or decrease in Nw? please clarify.
• 5) Line 315-316: This sentence is also unclear. Do you mean "a broader shape .... non-zero mu gamma DSD? If so, need a few more sentences to explain why large D0 and small lambda can represent non-zero mu.
• 6) Line 344 “even though breakup signal is obtained.”: I do not know why you need this phrase here. Break up or coalescence does not affect LWC. Breakup (increase of small raindrops and decrease of large raindrops) can increase LWC at a given Rain fall rate (because fall speed decreases).

Technical comments

1. Lines 21-22: Unclear sentence. Do you want to say "frequently observed in heavy rain events?"
2. Line 55 “recent studies”: The following study is not a recent study (in 2013, more than 10 years ago)
3. L first appeared here. Please define.
4. What type of disdrometer was used? Please provide the model or specifications.
5. Where is the radar location in Fig. 1?
6. Line 229: Does not need “is”
7. Lines 296: Did you remove large ZDR? Unclear.
8. Lines 311-312: This sentence is unclear. Please revise it.

See the attached file.