Geometrical and optical properties of cirrus clouds in Barcelona, Spain: analysis with the two-way transmittance method of 4 years of lidar measurements

Gil-Díaz, Cristina; Sicard, Michäel; Comerón, Adolfo; dos Santos Oliveira, Daniel Camilo Fortunato; Muñoz-Porcar, Constantino; Rodríguez-Gómez, Alejandro; Lewis, Jasper R.; Welton, Ellsworth J.; Lolli, Simone

doi:https://doi.org/10.5194/amt-17-1197-2024

Articles | Volume 17, issue 4

https://doi.org/10.5194/amt-17-1197-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-17-1197-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 4

Research article

|

20 Feb 2024

Research article |

| 20 Feb 2024

Geometrical and optical properties of cirrus clouds in Barcelona, Spain: analysis with the two-way transmittance method of 4 years of lidar measurements

Cristina Gil-Díaz, Michäel Sicard, Adolfo Comerón, Daniel Camilo Fortunato dos Santos Oliveira, Constantino Muñoz-Porcar, Alejandro Rodríguez-Gómez, Jasper R. Lewis, Ellsworth J. Welton, and Simone Lolli

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Final revised paper (published on 20 Feb 2024)
Preprint (discussion started on 21 Aug 2023)

Interactive discussion

Status: closed

RC1:
'Comment on amt-2023-134', Anonymous Referee #2, 23 Aug 2023

The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-134/amt-2023-134-RC1-supplement.pdf

Citation: https://doi.org/10.5194/amt-2023-134-RC1
- AC1:
  'Reply on RC1', Cristina Gil Díaz, 24 Oct 2023
  
  Dear reviewer,
  I attach a pdf document with detailed responses to your reviews.
  Thank you very much for the time spent in revising the manuscript.
  Best regards,
  Cristina Gil.
  
  Citation: https://doi.org/10.5194/amt-2023-134-AC1
  - CC2: 'Reply on AC1: contrails?', Ulrich Schumann, 24 Oct 2023
    
    Do you have a reply to the comments I send in September regarding contrails?
    
    Citation: https://doi.org/10.5194/amt-2023-134-CC2
    
    AC3: 'Reply on CC2', Cristina Gil Díaz, 26 Oct 2023
    
    Dear Dr. Schumann,
    I have replied in the thread that has been created, associated to your comments in the interactive discussion. Anyway, I attach here a pdf document with more detailed answers.
    Thank you very much for your contribution.
    Best regards,
    Cristina Gil.
    
    Citation: https://doi.org/10.5194/amt-2023-134-AC3
- AC5: 'Reply on RC1', Cristina Gil Díaz, 19 Dec 2023
  
  Dear reviewer,
  I attach a pdf with final detailed responses to your reviews. Some explanations and notation have been modified in order to improve the manuscript.
  Thank you very much for the time spent in revising the manuscript.
  Best regards,
  Cristina Gil.
  
  Citation: https://doi.org/10.5194/amt-2023-134-AC5
CC1:
'Comment on amt-2023-243: How much of the observed cirrus is contrail cirrus', Ulrich Schumann, 04 Sep 2023

This is an interesting study which might be extended by addressing further related questions in this or in follow-on papers.
Barcelona is often passed by airliners and other high-flying aircraft in the upper troposphere or lowermost stratosphere. For traffic details see, e.g., Teoh et al. (2023), still in discussion phase. Here quite often contrails are formed which persist under suitable humidity conditions (Schumann, 1996; Schumann and Heymsfield, 2017; Schumann et al., 2021; Li et al., 2023).
So, my question to you: Did the criteria you used to select your observed cirrus cases exclude contrails? And if yes, based on which criterium?
How much of your observed cirrus are in fact contrails?
Please note that contrails sometimes reach life times of several hours and may evolve to a large width (order 10 km or more) and depth (order 500 to 1500 m) and move with the wind over possibly large distances. Many contrails from various aircraft often overlap and form together a “contrail cirrus” cloud, hard to distinguish form other cirrus. Contrail cirrus and other cirrus often merge into one cirrus cloud. Individual contrails and contrail cirrus should have rather high concentrations of small ice particles and possibly still have a shape similar to a (disrupted) line structure (Vázquez-Navarro et al., 2015). This also affects Lidar depolarization rate measurements (Urbanek et al., 2018; Li and Groß, 2021; Groß et al., 2023).
In your paper you use radiosonde data but did not use humidity data. Why this restriction? The humidity data of modern radiosondes (e.g., of type RS41) should allow for useful measurements of humidity (dew point temperature) up to the tropopause. And the question for which humidity cirrus ice particles survive is still an ongoing topic of research. The degree to which relative humidity inside cirrus deviates from ice saturation might allow to estimate the ages of cirrus clouds.
As mentioned before, several of my comments require further research and hence are not the condition for publishing this paper, but you might include an outlook which addresses some of these topics.

References

Groß, S., T. Jurkat-Witschas, Q. Li, M. Wirth, B. Urbanek, M. Krämer, R. Weigel, and C. Voigt (2023). Investigating an indirect aviation effect on mid-latitude cirrus clouds – linking lidar-derived optical properties to in situ measurements Atmos. Chem. Phys., 23, 8369-8381, https://doi.org/10.5194/acp-23-8369-2023.
Li, Q., and S. Groß (2021). Changes of cirrus cloud properties and occurrence over Europe during the COVID-19-caused air traffic reduction. Atmos. Chem. Phys., https://acp.copernicus.org/articles/21/14573/2021/.
Li, Y., C. Mahnke, S. Rohs, U. Bundke, N. Spelten, G. Dekoutsidis, S. Groß, C. Voigt, U. Schumann, A. Petzold, and M. Krämer (2023). Upper tropospheric slightly ice-subsaturated regions: Frequency of occurrence and statistical evidence for the appearance of contrail cirrus. Atmos. Chem. Phys., 23(February), 2251–2271, https://doi.org/10.5194/acp-23-2251-2023.
Schumann, U. (1996). On conditions for contrail formation from aircraft exhausts. Meteorol. Z., 5(1), 4-23, doi: 10.1127/metz/5/1996/4, https://elib.dlr.de/32128/.
Schumann, U., and A. Heymsfield (2017). On the lifecycle of individual contrails and contrail cirrus. Meteor. Monogr., 58(3), 3.1-3.24, doi: 10.1175/AMSMONOGRAPHS-D-16-0005.1.
Schumann, U., I. Poll, R. Teoh, R. Koelle, E. Spinielli, J. Molloy, G. S. Koudis, R. Baumann, L. Bugliaro, M. Stettler, and C. Voigt (2021). Air traffic and contrail changes over Europe during COVID-19: A model study. Atmos. Chem. Phys., 21(10), 7429–7450, doi: 10.5194/acp-21-7429-2021.
Teoh, R., Z. Engberg, M. Shapiro, L. Dray, and M. E. J. Stettler (2023). A high-resolution Global Aviation emissions Inventory based on ADS-B (GAIA) for 2019 – 2021. EGUsphere, preprint, https://doi.org/10.5194/egusphere-2023-724.
Urbanek, B., S. Groß, M. Wirth, C. Rolf, M. Krämer, and C. Voigt (2018). High depolarization ratios of naturally occurring cirrus clouds near air traffic regions over Europe. Geophys. Res. Lett., 45, 13166-13172, doi: 10.1029/2018GL079345.
Vázquez-Navarro, M., H. Mannstein, and S. Kox (2015). Contrail life cycle and properties from 1 year of MSG/SEVIRI rapid-scan images. Atmos. Chem. Phys., 15, 8739-8749, doi: 10.5194/acp-15-8739-2015.

Citation: https://doi.org/10.5194/amt-2023-134-CC1
- AC2: 'Reply on CC1', Cristina Gil Díaz, 24 Oct 2023
  
  Dear Dr. Schumann,
  Thank you very much for the time spent reading the paper and for you contribution to it. I attach a pdf document with more detailed answers to your questions.
  Best regards,
  Cristina Gil.
  
  Citation: https://doi.org/10.5194/amt-2023-134-AC2
RC2:
'Comment on amt-2023-134', Anonymous Referee #3, 22 Nov 2023

The paper of Gil-Diaz et al., presents a statistical study of cirrus geometrical and optical properties based on 5 years of continuous groundbased lidar measurements with the Barcelona (Spain) Micro Pulse Lidar (MPL). An overview of the cirrus properties from literature is also presented, along with the dataset from Barcelona. The main results of the study could be of interest. However, the manuscript needs further work and improvements. The authors should point out the novelty of their study and re-organizing the structure of the paper that is not well structured. The following general and specific comments must be addressed before accepting the manuscript for publication.
General comment
According to authors, the detection of the cirrus clouds is made to fulfill two criteria, one about the temperature at the cloud top height and the other about the cloud base height. What about the signal to noise ratio, before applying the cirrus detection? The SNR should also be checked.
What about the smoothing that the authors apply to the lidar signal?
How can authors explain the detection of cirrus clouds with depolarization values less than 0.1? Figure 5 (right) is depicting linear cloud depolarization ratio in the bin between 0 and 0.1? Have you checked the SNR of these causes? The depolarization values are really surprising for cirrus clouds. Moreover, the 1-min temporal resolution could have restricted the accuracy of the depolarization ratio. Do the authors apply any integration for the cloud retrievals?
Authors claim that “For example, one of the major advantages of this new approach of the method is that it is only necessary to assume a Rayleigh zone both above and below the cirrus cloud, without making any priori optical and/or microphysical hypotheses about the cirrus Cloud”. The authors should provide more details and even calculations about the errors introducing in their statistics with this approach in detecting cirrus clouds.
Line 17. The authors claim that: «Together with results from other sites, a possible latitudinal dependence of lidar ratio is detected: the lidar ratio increases with increasing latitude.» This sentence is not supported from the study retrievals. It must be removed.
How is the calibration of the polar and cross-polar channel made?
In the equation #6, the η factor is equal to 1 in your study. You should state this assumption.
How CALIPSO accounts for the multiple scattering effect of the ice crystals?
Table 1 and its description is now included in the section of results. It should be moved before Section 4. I propose a reconstruction of the text.
The title of Section 4.4 “Cirrus correlation” is misleading. It must be changed.
Line 80-85. The novelty of the work needs to be discussed and detailed.
Specific comments
Page 2 line 44-45. Reference is missing.
Page 27, Line 590. Replace “Depolarizationratio” with “Depolarization ratio”.

Citation: https://doi.org/10.5194/amt-2023-134-RC2
- AC4: 'Reply on RC2', Cristina Gil Díaz, 19 Dec 2023
  
  Dear reviewer,
  I attach a pdf with detailed responses to your reviews.
  Thank you very much for the time spent in revising the manuscript.
  Best regards,
  Cristina Gil.
  
  Citation: https://doi.org/10.5194/amt-2023-134-AC4

Peer review completion

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

AR by Cristina Gil Díaz on behalf of the Authors (19 Dec 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (02 Jan 2024) by Alexander Kokhanovsky

AR by Cristina Gil Díaz on behalf of the Authors (08 Jan 2024)

Short summary

In this paper, a statistical study of cirrus geometrical and optical properties based on 4 years of continuous ground-based lidar measurements with the Barcelona (Spain) Micro Pulse Lidar (MPL) is analysed. The cloud optical depth, effective column lidar ratio and linear cloud depolarisation ratio have been calculated by a new approach to the two-way transmittance method, which is valid for both ground-based and spaceborne lidar systems. Their associated errors are also provided.