The manuscript describes the set-up, attitude control, and exemplary measurements of two vertical pointing radars onboard RV MS Merian during Eurec4a. Main focus of this data paper is the compensation of the ship motion in situations where the active stabilization platform was properly working and different treatment of data in situations where the platform got stuck in arbitrary orientations.

The manuscript is consistent and well written and certainly deserves publication as data paper. There are only minor modifications required. I like the lessons learned section, I hope that this will be considered in future campaigns.

Some general comments:

Obviously, the authors did develop the methods behind the ship motion correction by themselves, without borrowing from the airborne radar community (e.g. Bange, J. et al., 2013: Measurement of aircraft state and thermodynamic and yynamic variable, in: Airborne Measurements for Environmental Research: Methods and Instruments, edited by: Wendisch, M. and Brenguier, J-L., https://doi.org/10.1002/9783527653218.ch2). The methods are the same and there is an agreement between the two worlds (air - sea).

For the W-band radar you do not mention anything about attenuation (gaseous, liquid) which certainly has to be considered, you call it just reflectivity (factor). Whereas for the MRR you talk about attenuated equivalent reflectivity (factor). This should be consistent. Otherwise one might assume that data from W-band radar are corrected for gaseous and liquid attenuation as well as for Mie effects. Reflectivity factor z implies Rayleigh approximation. However, since both systems are mm-wave systems you better write about effective reflectivity factor. This implies that Mie scattering effects have to be considered in the interpretation of reflectivity factor.

I think the labels/numbers in the figures are too small, but I leave this to the technical editor.

Minor specific comments and hints in the order of appearance in the text:

Line 14: I think DOI's have to be given in the abstract, but this is a task for the technical editor

Line 22: What does OA stand for?

Line 69: Section instead of Session

Line 78: can you give here some numbers about the temporal drift

Line 127: Why longitude and latitude with the same temporal resolution as the radar data are not copied to the radar dataset?

Lines 170 - 175: can you also give the temporal resolution of the MRU?

Lines 179 - 184: this should go to section 2.3

Figure 5 is hardly readable, the sketch of MS Merian is 2D, whereas the vectors are 3D; this figure should be improved considerable

Lines 206 + 207: “whereas w_heave … gates” is repeated from above

Lines 224 - 230: confusing, ex,ey,ez  is first ship relative and later horizon relative, maybe you could use different notations for the two reference systems

Line 226: appendix C or equation C4

Figure 6: faint lines are hard to read, you could also use dashed lines instead

Line 239: horizontal or ship relative coordination system? These are different reference systems

Line 262: v_trans would be more memorable for the translation velocity than v_trasl

Line 264? - rotation vector: what is about bending and twisting of the ship body (I remember a video you showed once at a workshop)

Figure 7: maybe panels a), b), c), e), f), g) could be larger, and d) and h) could be smaller (or omitted)

Line 296: Figure 7 e)-g)

Line 298: the high fall velocities in the second half of the plot and persistent through all heights seem unrealistic, can you comment on this?

Line 311: signal to noise "ratio"

Line 313: Table 2 gives 7.5 to 34 m resolution. For the horizontal resolution also beamwidth has to be considered

Line 321: numbering Fig. A1 is confusing. The figure does not belong to Appendix A

Figure 9 caption: interpretation “and made a hook rain structure … wind mixing” should not go to caption

Figure 12: I think, images from both radars should have the identical height axis range and identical color bar range and color map. This makes comparisons between W- and K-band much easier, even though it is not the objective of the paper.

Line 399: It might be worth to discuss shortly the observed differences between both radars and how the complement each another. Different attenuation due to different wavelengths, different sensitivity, …

Line 434: just a comment: some airborne systems (unfortunately not HALO/HAMP) have an IRS/IMU as close as possible to the radar antenna

Line 507: … by alpha clockwise from North

Line 507: for non-meteorologists you could add "(the direction where the wind is coming from)” this makes it easier to understand the minus signs in Eq. B1

Line 514: If “yaw” psi is indeed …

Line 523: heave is not discussed here

Line 531 till end of page: check order of description of r_rot and v_rot, looks like repeating of definitions

Line 544, Eq. D1: should be e_p0 = … (?)

Line 547, Eq. D2: why not t_final for theta_tbl,S

Acquistapace et al. describe in this paper the deployment, operation and data processing of two radar systems (W-band cloud radar and micro rain radar) on the research vessel Maria S. Merian during the EUREC4A campaign in early 2020. They describe the setup of the radars on a stabilization platform and the correction of measured Doppler velocities, both for times when the stabilization platform was operational and when it was stuck in an arbitrary position.

The manuscript is well written and clearly structured. The data set is easily accessible.

I have a some comments and would recommend publication after addressing those.

General comments regarding the data:

It would be nice, if the data for ship motion was published along with the latest version of the radar data. Now, users have to access different data sets. And this also adds the danger of possibly using outdated radar data that are published along with the ship motion data (https://doi.org/10.25326/156) and could confuse some users.

Is there a way to access ship location information to use together with the hourly data? What would users need to do if they want to know where the Maria S. Merian was located for a specific hourly data file?

Specific comments regarding the manuscript:

Figure 3: it is a bit unclear to me, what this figure should convey. The processing steps that are shown in the figure are not easily understandable by just looking at it. A lot of necessary information is given in the figure caption. One could think about adding these additional information from the caption also into the figure itself. The order in which the steps are mentioned in the caption does not match the order in the figure. I would suggest to either expand this figure a bit so that the processing steps are understandable by only looking at the figure or to remove the figure and expand the respective text section to thoroughly explain the processing steps. In the current state, the processing is a bit hard to follow between the figure, the caption and the text.

Line 157: "computer in a sealed container", what is the meaning behind this? What does the computer do? Is the information necessary? Also, does it have any impact that the container is sealed?

Section 2.3: What are the limits of the stabilization platform compensation? I.e. maximum roll and pitch angles that can be compensated? Was this relevant during this campaign?

Figure 5: this figure is hard to read in the current state. The ship's drawing in the background distracts from the coordinate axes plotted on top and is not necessary to understand the different rotation angles when the figure is first mentioned. I understand, that this figure is referenced later as well as an example on how the coordinate system is defined with respect to the ship. Could this figure be split into two figures for the different purposes?

Line 193: "... time lag ∆T that varies with time between 1 and 4 s" is the variation systematic (e.g. linear increase over the measurement duration)? Or are these random variations?

Line 214 and following: was the time correction done for each time step individually or was this applied to longer intervals?

Line 373: "... cloud system identifiable as a flower type ..." It might be helpful for the reader to add a reference describing the different cloud organization names here.

Line 513: what is psi? If this is the yaw angle and the difference between psi and heading can be something other than zero, I don't understand why heading and yaw are used interchangeably in other parts of the manuscript (e.g. l167 (p9, second paragraph, third line), l523).

Line 547, line 552: what is t_fin? Should it be t_final?

Figure A1: The vertical lines in A) and B) are only barely discernible or not at all. Maybe using another colormap (something like the ones used for the other figures in the manuscript) would help? The authors switch between lower case and upper case letters for the different figure parts between the figure itself and the figure caption and even within the figure caption.

Technical corrections

Line 8: hydrometeors -> hydrometeor

Line 33: time -> temporal

Line 35: setup -> setups

Line 127: add lat, lon as coordinates to the text

Line 188: I don't understand the use of the word "preliminary" here.

Line 475: "in agreement with what reported in" -> "in agreement with what was reported in"

Table 3: unit [deg C] not italic

Review of “EUREC4A’s Maria S. Merian ship-based cloud and micro rain radar observations of clouds and precipitation” by Acquistapace et al.

The manuscript introduces the radar data sets collected during the EUREC4A campaign between trade wind region and tropical convergence zone on the research ship Maria S. Merian. The data set is unique and of high interest for the community. Necessary post-processing and some derived products published alongside the manuscript are presented. This manuscript deserves publication after correction of quite a number of small weaknesses and inaccuracies in the presentation.

Questions to the editorial office rather than the authors arise from the use of webpage referencing and a reference to an unpublished manuscript.

General points:

The introduction and beginning of the section 2 left me confused about what to expect in this paper. Please be specific about what you will provide in this data set as early as possible. In the manuscript it only becomes clearer step by step. IWV is first mentioned in the beginning of section 2. LWP somewhat later, before IWV is detailed again. I would suggest to mention all these in the introduction and add a product table of all data set, their sampling rate, their expected accuracy, etc.

The authors should be clearer and more specific about the limitations of all their steps. Starting from active positioning, but also about the accuracy of all data sets published. … Data without accuracy information is no data.

In section 3.1 and 3.2 the nomenclature should be checked again. I have the impression that not all nomenclature is used correctly and some quantities are labelled in different ways.

Please check, if all appendices are mentioned in the text. I only found references to App. A, C, D.

Minor and specifics:

Minor language editing will be needed as sentences are ill-constructed from time to time.

l.6: I would prefer not to use manufacturer product names in the abstract. The “PRO” in “MRR-PRO” is not needed and it’s not introduced. Stay more general and leave out the “PRO” until you introduce the product in the “Experimental setup” section.

l.20: “oceanic eddies”. These show up uncommented and seem to be important. Can you add a sentence on what it is and why it is interesting?

L22: “OA”. Please introduce.

l.28: “MRR-PRO”. As before.

L33: “… spatial and time resolution of the entire precipitation life cycle.” Of what? Daily, seasonal, global, local?

l.42/43: “9 s”. Where does this information come from? Measurement during the campaign? Does the “(Chris Fairall,…)” refer to them? Because the fact that a wavelength of 9 s needs measurements of at least 2 s to represent is mathematically obvious and would not need any support.

l.47: “additional measurements onboard”. Please add a "not presented/published here".

l.61-63: “Active remote … satellite retrievals.” This is a bit repetitive. Please remove.

l.74-77: “We calibrated … factory calibration.” This should be part of the instrument specific 2.1 and 2.2.

l.81: “We launched …”. This reads as if you will also present these for a moment. Please be precise what to expect from this manuscript.

l.81: “descents”. What is this?

l.83: More pieces pop up. You never said that you will provide an IWV data set, did you?

l.107: The ANN retrieval of the manufacturer is not documented anywhere? No reference?

l.114: Didn't you say that the atmosphere is relatively gas-transparent. How big are your errors? Usually other frequencies are used for IWV! Please comment. This probably only works, because of your dense and closely related radiosonde data? Which different radar "reflectivity values" are you talking about? Why plural?

l.132: I’m missing the products IWV and LWP.

l.142: Only this is where you should introduce the “PRO” part in MRR-PRO. “PRO” most likely is the “Professional” one. Only manufacturer terminology, but tell us.

l.146: This sentence seems awkward. Please re-phrase.

Fig. 3: This is “method” not “experimental setup”, isn’t it? Wouldn’t this better fit into 3.2 or 3.4?

Tab.1: “spectral bins”, “spectral resolution”. This refers to the Doppler Fourier spectrum? Please clarify.

l.167: At the end of this section. What are the limitations of this positioning correction? What is the frequency of correction steps? And how does this fit to expected and observed roll and pitch values and radar sampling? Where do the mentioned 35% come from? Please clarify.

Top paragraph on page 9 (line numbering mixed up): What is the frequency of MRU position measurements? You have not mentioned it anywhere.

Page 9: There seems to be an 1,70 m offset between W-band and MRR. The image does not show this. Please comment.

Fig 5: The combination of axes sketch and image in the back is confusing. First it looks as if you show a pitch angle. Then it takes some time to detect that you show an arbitrary combination of all three. Can you improve that? Maybe by changing the ship display and/or moving it away from the center of the figure? And where is the arrowhead of the y-axis?

l.200: “downdraft”. The radar rather sees the downward motion of droplets and not the downdraft of the air. Please correct.

L.215: Whole paragraph. Above you stated that you use a 20 min time window. Here you state that it is done for every radar chirp. Please explain at what frequency you derived the DeltaT. And please, say a few words about likely reasons of the time offset. I can imagine that a time offset of several seconds between instruments develops over time. An erratic variation over the campaign is something I would not understand.

l.233/234: Didn't you just explain the same facts using the terms v_d and v_hyd in section 3.1? Please explain the difference once more, if needed. Otherwise please adjust nomenclature and remove repetitions.

l.259: Please comment on the need to label this data as "limited quality" here.

Page 13, bottom (line numbering broken again). “intensity” à “magnitude” of a vector?

L.268, eq 8: Reads like vectors are subtracted from a scalar?! It should be italic "v"s in the equation 8. On the other hand, it is not intuitive to label the z-component with another letter that "w"? Do you need another definition here? Please clarify and simplify nomenclature.

L.280: The first part of 3.3 reads slightly repetitive, apart from the horizontal wind influence. I think this part would better fit as last summarizing point in section 3.2.

l.284-292: This is why I'm still missing some information on accuracy of all these corrections in the different situations and some suggestions how to deal with them when using the data! Please add this information.

l.296: “Figure 7d)-h).” No d) and h) only show the platform status. e,f,g show the performance.

l.302: “as described by looking at…” and Fig 8. …. I'm confused. I assume that this is a Fourier spectrum of the time series of vertical motion? Correct? In a certain cloudy range gate you can see the Doppler velocity fluctuation combined from particles’ fall speed and ship motion w_signal. You cannot see the "vertical motion of the radar" v_rad which results from the ship motion, can you? Please mention equations 2, 7 and 8  and explain better.

Fig. 8: I guess it should be frequency in "1/s" or better "Hz" on the x-axis? And the top label "periods" à “period”.

l.308: Is this the right range? 0.5 Hz is in the middle of your x axis!? See next point.

l.310: This smooths the part between above 0.1 = 10 s period, correct? Above you state the range 0.1 to 0.5 Hz which would be period range 10 s - 16 s !?

l.311: Confusing sentence. And basically nothing you need to put into an equation. Mean speed multiplied with time is distance. Remove it.

l.333: “Prominence” is not a mathematical term. Please define.

L339: “lowest 600 m”. Please give the reason why this assumption/ condition is justified.

l.342: "abrupt"? Please explain a bit. What reason could there be to accept 2 or 3? The same is true for point 3 in l.343. At least explain why, if they are all found empirically.

l.373: I wonder if "flower" has made it to general technical language already. Please explain EUREC4A slang.

L378: “difficult to quantify”. Uuh. Isn't this what a data publication should provide? Best estimates of accuracy of the published data? If you cannot provide any accuracy you should not publish it at all? Please think about a way to provide some estimate on this.

l.385: “Fig 12 b) displays clear areas”. I'm confused. I don't see clear areas in b), I see them in a)? In addition, some explanation would be nice. Why is it clear in a) when I see large negative values in b)?

l.399: Please explain. LWP includes the rain. How does it contaminate the measurement?