Discussion of the spectral slope of the lidar ratio between 355 and 1064&thinsp;nm from multiwavelength  Raman lidar observations

Haarig, Moritz; Engelmann, Ronny; Baars, Holger; Gast, Benedikt; Althausen, Dietrich; Ansmann, Albert

doi:https://doi.org/10.5194/acp-25-7741-2025

Articles | Volume 25, issue 14

https://doi.org/10.5194/acp-25-7741-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-25-7741-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 25, issue 14

Research article

|

22 Jul 2025

Research article |

| 22 Jul 2025

Discussion of the spectral slope of the lidar ratio between 355 and 1064 nm from multiwavelength Raman lidar observations

Moritz Haarig, Ronny Engelmann, Holger Baars, Benedikt Gast, Dietrich Althausen, and Albert Ansmann

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Final revised paper (published on 22 Jul 2025)
Preprint (discussion started on 11 Feb 2025)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-449', Anonymous Referee #1, 27 Feb 2025

The lidar group in Leipzig began measuring the extinction coefficient at 1064 nm in 2016, and this manuscript presents a comprehensive summary of observations. Until recently, information on the lidar ratio at 1064 nm and the Ångström exponent at 532/1064 nm was unavailable, and this study addresses that gap. For different aerosol types, the manuscript provides valuable new insights into the dependence of key parameters—backscattering and extinction coefficients, lidar ratio, and growth factors—on relative humidity.
The measurements were conducted at three wavelengths, allowing for an analysis of the spectral dependence of these parameters. The authors are well-recognized experts in the field of lidar measurements. The manuscript is well-written, includes a thorough review of existing literature, and is, in principle, suitable for publication as is.
The only minor comment concerns Fig. 3. While visually appealing, its necessity in the manuscript is unclear.

Citation: https://doi.org/10.5194/egusphere-2025-449-RC1
- AC1: 'Reply on RC1', Moritz Haarig, 17 Apr 2025
  
  Dear Anonymous Reviewer,
  We thank you for your time and effort spent to check our manuscript. And we are delighted that it meets your expectations.
  Concerning Figure 3, I completely agree with you, that the photograph of the 5 lidar beams at our institute is not necessary to understand the content of the study. It is more a kind of ornament or decoration, it is an additional illustration as it was done in old books centuries ago. And as such I would like to keep it in the manuscript.
  We went over the text and improved some formulations (see track changes) and found a minor bug in the fitting of the hygroscopic growth parameter of the lidar ratio (now 0.45 instead of 0.49, the uncertainty changed only below the given significant digits). The optical profiles used for the two presented case studies were made available via zenodo.
  Kind regards,
  Moritz Haarig in the name of all co-authors
  
  Citation: https://doi.org/10.5194/egusphere-2025-449-AC1
RC2:
'Comment on egusphere-2025-449', Anonymous Referee #2, 06 Mar 2025

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-449/egusphere-2025-449-RC2-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2025-449-RC2
- AC2: 'Reply on RC2', Moritz Haarig, 17 Apr 2025
  
  Dear Anonymous Reviewer,
  We thank you for your time and effort spent to check our manuscript. Your comments are very helpful in improving the study. Especially, the discussion about the smoke lidar ratios and what we know and what not, profited from your input.
  The detailed reply to your comments is provided in the attached pdf.
  Kind regards,
  Moritz Haarig in the name of all co-authors
  
  Citation: https://doi.org/10.5194/egusphere-2025-449-AC2

Peer review completion

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

AR by Moritz Haarig on behalf of the Authors (17 Apr 2025) Author's response Author's tracked changes Manuscript

ED: Publish subject to minor revisions (review by editor) (30 Apr 2025) by Eduardo Landulfo

AR by Moritz Haarig on behalf of the Authors (30 Apr 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (30 Apr 2025) by Eduardo Landulfo

AR by Moritz Haarig on behalf of the Authors (06 May 2025) Manuscript

Short summary

The lidar ratio is an important quantity in aerosol typing. Its spectral slope contains information about the source region or transport paths of the observed aerosol. The extension to 1064 nm is a recent development led by our institute. We gathered previous observations and added new ones to provide the spectral slope for the most important aerosol types such as marine and continental aerosol, dust, smoke, and sulfate. We compared it to assumptions used for spaceborne backscatter lidars.