Raindrop size distribution (DSD) during the passage of tropical cyclone Nivar: effect of measuring principle and wind on DSDs  and retrieved rain integral and polarimetric parameters from impact and laser disdrometers

Radhakrishna, Basivi

doi:https://doi.org/10.5194/amt-15-6705-2022

Articles | Volume 15, issue 22

https://doi.org/10.5194/amt-15-6705-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-15-6705-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 22

Research article

|

21 Nov 2022

Research article |

| 21 Nov 2022

Raindrop size distribution (DSD) during the passage of tropical cyclone Nivar: effect of measuring principle and wind on DSDs and retrieved rain integral and polarimetric parameters from impact and laser disdrometers

Basivi Radhakrishna

Download

Final revised paper (published on 21 Nov 2022)
Supplement to the final revised paper
Preprint (discussion started on 19 Aug 2022)
Supplement to the preprint

Interactive discussion

Status: closed

RC1:
'Comment on amt-2022-209', Anonymous Referee #1, 31 Aug 2022

This manuscript describes the observations collected by three surface disdrometers (i.e., JWD, LM, and PARSIVEL) during the passage of a Tropical Cyclone. There are a few confusing sentences that need to be clarified before publishing.

1. Abstract. Lines 10-12 state, “Raindrops greater than 3 mm in size are infrequent in the JWD recordings while frequent in the LPM an PARSIVEL indicating JWD underestimates the size of the raindrops than LPM and PARSIVEL due to canting of raindrops in the presence of wind.” This sentence suggests the JWD underestimates raindrops greater than 3 mm diameter because the raindrops are canted in the presence of wind. This is inconsistent with conclusion #1 (lines 345-348) that states “The canting of raindrops in the presence of large horizontal winds results in more residing time in the laser beam resulting in an additional reduction in the beam intensity at the receiver. Thus, the conclusion suggests the laser disdrometers overestimate the size of the raindrops in the presence of horizontal winds.” I believe the abstract needs to be corrected to match the conclusion.

2. Lines 10-12 (abstract), 233-236 (body) and 345-348 (conclusion). The word “canting” only occurs in the abstract and conclusion. The body (lines 233-236) discusses why the laser disdrometers observe larger raindrops in high wind cases because the raindrops have a longer path through the laser beam. This longer path is not a raindrop canting. The three disdrometers cannot measure canting angle (the JWD measures momentum, and the two laser disdrometers only have one imaging dimension). Please clarify the manuscript and be consistent between abstract, body, and conclusions.

3. Equations (1) to (6). I am confused by what processing was performed by the disdrometer and what processing was performed by the author. Please clarify in the text which processing steps described in equations (1) to (6) produced N(D) as an output from the disdrometers and which processing steps were needed to calculate N(D) off-line.

Citation: https://doi.org/10.5194/amt-2022-209-RC1
- AC1: 'Reply on RC1', Basivi Radhakrishna, 01 Sep 2022
  
  At the outset, the author wants to thank the reviewer for his patience in reading and suggesting improvements to the manuscript.
  Reviewer#1
  Comment: This manuscript describes the observations collected by three surface disdrometers (i.e., JWD, LM, and PARSIVEL) during the passage of a Tropical Cyclone. There are a few confusing sentences that need to be clarified before publishing.
  Reply: The confusing statements are rewritten with better clarity in the revised manuscript.
  
  Comment: 1. Abstract. Lines 10-12 state, “Raindrops greater than 3 mm in size are infrequent in the JWD recordings while frequent in the LPM an PARSIVEL indicating JWD underestimates the size of the raindrops than LPM and PARSIVEL due to canting of raindrops in the presence of wind.” This sentence suggests the JWD underestimates raindrops greater than 3 mm diameter because the raindrops are canted in the presence of wind. This is inconsistent with conclusion #1 (lines 345-348) that states “The canting of raindrops in the presence of large horizontal winds results in more residing time in the laser beam resulting in an additional reduction in the beam intensity at the receiver. Thus, the conclusion suggests the laser disdrometers overestimate the size of the raindrops in the presence of horizontal winds.” I believe the abstract needs to be corrected to match the conclusion.
  Reply: Compared to JWD, LPM and PARSIVEL disdrometers record raindrop with size greater than 3 mm. To avoid confusion, the sentence is modified as follows in the revised manuscript. LPM and PARSIVEL overestimates the raindrop size when the fall path deviates from nadir due to horizontal wind.
  Comment: 2. Lines 10-12 (abstract), 233-236 (body) and 345-348 (conclusion). The word “canting” only occurs in the abstract and conclusion. The body (lines 233-236) discusses why the laser disdrometers observe larger raindrops in high wind cases because the raindrops have a longer path through the laser beam. This longer path is not a raindrop canting. The three disdrometers cannot measure canting angle (the JWD measures momentum, and the two laser disdrometers only have one imaging dimension). Please clarify the manuscript and be consistent between abstract, body, and conclusions.
  Reply: I completely agree with the reviewer that canting of raindrops cannot be measured by the disdrometers used in the study. The context is to portray the deviation of raindrop fall path from nadir. Hence, in the revised manuscript the canting of raindrops is replaced with deviation of fall path from nadir.
  Comment: 3. Equations (1) to (6). I am confused by what processing was performed by the disdrometer and what processing was performed by the author. Please clarify in the text which processing steps described in equations (1) to (6) produced N(D) as an output from the disdrometers and which processing steps were needed to calculate N(D) off-line.
  Reply: The processing performed by the manufacturer of disdrometer indicates the converting of electrical signals into number of drops in each drop diameter interval.
  After obtaining the number of drops information in each diameter interval, equations (1) to (6) are used to estimated N(D).
  
  Citation: https://doi.org/10.5194/amt-2022-209-AC1
RC2:
'Comment on amt-2022-209', Anonymous Referee #2, 16 Sep 2022

Please see the attached review.

Citation: https://doi.org/10.5194/amt-2022-209-RC2
- AC3: 'Reply on RC2', Basivi Radhakrishna, 05 Oct 2022
  
  The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2022-209/amt-2022-209-AC3-supplement.pdf
  
  Citation: https://doi.org/10.5194/amt-2022-209-AC3
RC3:
'Comment on amt-2022-209', Anonymous Referee #3, 16 Sep 2022

The manuscript describes the observations during the cyclone overpass by three disdrometers that could help to know the characteristics of cyclonic DSDs and disparities in the observations. The quantification of errors is highly essential as they surface DSD measurements are used as reference datasets to calibrate radars. The manuscript is well written and easy to follow. However there are certain portions that needs to be improved before publishing in AMT.

The author compares at certain portions JWD with LPM and PARSIVEL and other times in vice versa. As suggested by Tokay et al. and the references therein, it could be good to keep JWD as reference and compare other two disdrometers with JWD will improve the readability of the manuscript.

Can the author show ZDR differences at different diameters at X-band? Although a reference is mentioned, but it could be good to provide the information in the manuscript.

Citation: https://doi.org/10.5194/amt-2022-209-RC3
- AC2: 'Reply on RC3', Basivi Radhakrishna, 27 Sep 2022
  
  The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2022-209/amt-2022-209-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/amt-2022-209-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Basivi Radhakrishna on behalf of the Authors (05 Oct 2022) Author's response Manuscript

EF by Polina Shvedko (07 Oct 2022) Author's tracked changes

ED: Referee Nomination & Report Request started (07 Oct 2022) by Zamin A. Kanji

RR by Anonymous Referee #3 (19 Oct 2022)

RR by Anonymous Referee #2 (24 Oct 2022)

ED: Publish subject to minor revisions (review by editor) (24 Oct 2022) by Zamin A. Kanji

AR by Basivi Radhakrishna on behalf of the Authors (25 Oct 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (30 Oct 2022) by Zamin A. Kanji

AR by Basivi Radhakrishna on behalf of the Authors (31 Oct 2022) Manuscript

Short summary

Raindrop size distributions (DSDs) measured by various types of disdrometers are different in the same environmental conditions. The mass-weighted mean diameter (D_m) measured from JWD is larger, and ZDR is smaller than LPM and PARSIVEL due to the resonance effect at X-band frequency. The effect of wind on DSD measured by various disdrometers is not uniform in different regions of a tropical cyclone.