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https://doi.org/10.5194/egusphere-2023-112
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2023-112
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
28 Feb 2023
| 28 Feb 2023
A Comparative Analysis of In-Situ Measurements of High Altitude Cirrus in the Tropics
Abstract. We analyze cirrus cloud measurements from two dual-instrument cloud spectrometers, two hygrometers and a backscattersonde in view to connect cirrus optical parameters usually accessible by remote sensing with microphysical size resolved and bulk properties accessible in situ. Specifically, we compare the particle backscattering coefficient and depolarization ratio to the particle size distribution, effective and mean radius, surface area density, particle aspherical fraction and ice water content. Data have been acquired by instruments on board the M55 Geophysica research aircraft during July and August 2017 during the Asian Monsoon campaign based in Kathmandu, Nepal, in the framework of the StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) project. Cirrus have been observed over the Hymalaian region between 10 km and the tropopause, situated at 17–18 km. The observed particle number densities varied between 10 and 10-4 cm-3 in the dimensional range from 1.5 to 468.5 μm in radius. Correspondingly, backscatter ratios from one tenth up to 50 have been observed.
Optical scattering theory has been used to compare the backscattering coefficient computed from measured particle size distribution with those directly observed by the backscattersonde. The aspect ratio of the particles, modeled as spheroids for the T-matrix approach, was left as a free parameter to match the calculations to the optical measures. The computed backscattering coefficient can be set in good agreement with the observed one, but the match between simulated and determined depolarization ratios is insufficient, however. Relationships between ice particle concentration, mean and effective radius, surface area density and ice water content with the measured backscattering coefficient are investigated for an estimate of the bulk microphysical parameters of cirrus clouds from remote sensing lidar data. The comparison between particle depolarization and aspherical fraction as measured by one of the cloud spectrometers equipped with a detector for polarization, represents a novelty since it was the first time the two instruments are operated simultaneously on aircraft. The analysis shows the difficulty of establishing an univocal link between depolarization values and the presence and amount of aspherical scatterers. This suggests the need of further investigation that could take into consideration not only the fraction of aspheric particles but also their predominant morphology.
How to cite. Cairo, F., Krämer, M., Afchine, A., Di Liberto, L., Khaykin, S., Lucaferri, L., Mitev, V., Port, M., Rolf, C., Snels, M., Spelten, N., Weigel, R., and Borrmann, S.: A Comparative Analysis of In-Situ Measurements of High Altitude Cirrus in the Tropics, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-112, 2023.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Journal article(s) based on this preprint
27 Oct 2023
A comparative analysis of in situ measurements of high-altitude cirrus in the tropics
Francesco Cairo, Martina Krämer, Armin Afchine, Guido Di Donfrancesco, Luca Di Liberto, Sergey Khaykin, Lorenza Lucaferri, Valentin Mitev, Max Port, Christian Rolf, Marcel Snels, Nicole Spelten, Ralf Weigel, and Stephan Borrmann
Atmos. Meas. Tech., 16, 4899–4925, https://doi.org/10.5194/amt-16-4899-2023, https://doi.org/10.5194/amt-16-4899-2023, 2023
Short summary
Short summary
Cirrus clouds have been observed over the Himalayan region between 10 km and the tropopause at 17–18 km. Data from backscattersonde, hygrometers, and particle cloud spectrometers have been compared to assess their consistency. Empirical relationships between optical parameters accessible with remote sensing lidars and cloud microphysical parameters (such as ice water content, particle number and surface area density, and particle aspherical fraction) have been established.
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
| : Report abuse
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RC1: 'Comment on egusphere-2023-112', Anonymous Referee #1, 17 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-112/egusphere-2023-112-RC1-supplement.pdf
- AC1: 'Reply on RC1', Francesco Cairo, 29 May 2023
-
RC2: 'fascinating results', Anonymous Referee #2, 24 Apr 2023
In this article, the authors present measurements performed in-situ from many airborne probes that flew within high-altitude cirrus clouds over South Asia during 7 hours over 7 flights. Among those probes, the most interesting was admittedly a backscattersonde called MAS which provided in-situ measurements in extremely close vincinity to the M55 plane (with near-zero overlap). The authors feed the Particle Size Distributions found by the in-situ probes into optical calculations to compute the Backscatter Ratio (BR) that would be observed considering a large range of possible particle Aspect Ratios (AR). By matching at each time frame the observed BR to the computed ones, the authors derive the particulate AR. Their results show it is possible to reproduce the measured BR with high fidelity and document the AR. They find that the measured BR is almost directly proportional to the ice crystal concentration. Finally, they also contrast the BR and derived particulate AR to the depolarization ratio observed in-situ by the MAS, but these efforts are frustratingly met with less success.In this paper the authors provide simultaneous in-situ and lidar-like measurements of ice crystals within cirrus clouds. This is amazing and, to my knowledge, unique. I was delighted to learn of the existence of the MAS backscattersonde. Having this kind of measurements and results (again, it's a bit hard for me to believe they do exist) published is very, very useful for people who wish to interpret lidar measurements within ice clouds. The work done and presented here is very important and useful. I share the authors' frustration with the difficulty to interprete depolarization measurements, but their results (even though inconclusive) provide important information and shed new light on the interpretation of depolarization measurements. I completely support this paper for publication. I have a few minor remarks below that the authors could take into account.
Minor comments
- l. 90 - "modelling of the optical properties of cirrus clouds is a formidable problem..." I share the authors' pain. The rest of the paragraph provides a nice review of previous efforts tackling this problem, but I'm not sure it brings a lot to the current discussion.
- section 2 -- the number of instruments is a bit large, and a table or a figure summarizing them would be nice.
- l. 132 - "the resolution is 10 s" -- I was surprised by this (relatively) very long sampling interval. It is worse than the 5 s mentioned in Cairo and al 2011. This means the MAS samples one point every 1 or 2km, which is quite a large distance. Are there ways to improve this?
- Figure 1 (1) : it is unclear to me why in Figure 1 the highest concentrations of points are not located at BR=1 ? Since clouds show up on 7 hours from the entire 35 hours of measurement, I would expect most of the points sampled by the MAS to be cloud-free, and thus to produce a BR=1 measurement. Could you please clarify my misunderstanding?
- Figure 1 (2) : could you specify in the legend the total number of data points?
- l. 158: "a negative trend with respect to temperature can be discerned" this is also reportedly the case in CALIPSO data, Sassen et al 2009 -- but I agree this trend is frustratingly hard to document quantitatively.
- In Methods : couldn't the CCP probes provide info about the particle aspect ratio? Such info could then be compared to the AR retrieved from the beta fit. Or do you think the aspect ratios from probes are too uncertain?
- l. 250: there is something wrong with the URL, I'm guessing the underscores were swallowed by the formatting system.
- l. 255: clicking the URL here brought me to the American Express website.
- l. 263-266: there is a problem with formatting here
- l. 272: missing period
- l. 371: this paragraph suddently mentions beta NC. I think this is the first time in the paper that beta NC is mentioned, and I don't think it is defined. Is beta NC the best match for the measured beta among the simulated beta AR NC ?
- Figure 3 (1): have you tried to create a scatterplot of depolarization vs AF? vs AR? of AF vs AR? Could you perhaps write the various labels of the vertical axis in the same color as their associated plot? It would make it easier to parse the figure.
- Figure 3 (2): is the AR retrieval at each time stamp completely independent from the previous retrievals? In some parts of the plot it looks like the retrievals are "stuck" at AR=3.
- Figure 3 (3): Figure 3, like most of the figures, is a bit on the small / crude side. This makes reading the figure harder than it should. Could you please produce higher-res versions of figures next time?
- Figure 3: I understand this is a bit outside the scope of the paper, but it would be very interesting to document the spatial scales over which depolarization is homogeneous.
- l. 400: "(19000s and 21000s)" what are those numbers? Can they be found somewhere on a figure? On Figure 3 times only go from 33000 to 38000.
- l. 400-405: Are the MAS/MAL depolarization ratios similarly correlated? Does the results from figure 4 suggest it is possible to use MAL measurements instead of MAS when more practical?
- Figure 4: Using a square aspect ratio in Figure 4 would make sense
- Figure 5 and 6: Having both as subplots of the same figure would help the reader. In Figure 5 I find it confusing that the y-axis says "Backscatter coefficient NIXE-CAPS" -- the NIXE-CAPS does not measure the backscatter coefficient. Same for figure 6.
- l. 419: "From the inspection of Figure 6 we can see an attempt to achieve a 1-1 correlation between the two datasets". I don't understand this sentence.
- l. 421: "the optical modelling completely fails" -- completely is perhaps a strong word, sometimes the retrieval is correct. But I agree it's perhaps worse than chance, the performance is very poor.
- l. 444 : "most of them are so called irregulars" how do you know this? Is this based on CCP imagery?
- l. 476: "We remind again that" perhaps with some editing it would be possible to avoid two reminders
- l. 477-485: This discussion is great. Based on Figure 12, wouldn't it be possible to combine the measured volume depolarization ratio and BR to retrieve the particulate/aerosol depolarization ratio (by extending the "line" these two measurements fall on all the way to the right), and use it instead of the volume depolarization ratio throughout your study? You might find better correlation with the AR time series.
- l. 490-493: It is not clear to me what is learned from Figure 13. The strong correlation between BR and Nice has already been shown before.
- Figure 15 is fascinating. Could you comment on whether particle orientation could have an effect on the volume depolarization ratio measured by the MAS, considering the specific MAS setup? Electric charging linked to lightning activity could lead to vertically-oriented particles, that would show planar faces to the MAS. Do you have any idea if the variable dynamic conditions (lines 500-504) could be disambiguated somehow by observation?
- l. 508: "a measured aspect ratio would be an obvious candidate" -- I was under the impression imagery from the CCP could provide this kind of retrieval.
- l. 579: From the start, it is not clear to me what is to be gained from following this path. Could you expand a bit on what you hoped to achieve with this?
- l. 590: "this may induce an unquantified bias in our presented statistics" -- I'm not sure I understand the point this paragraph is trying to make. Do you wish to state that the results you present here are not necessarily representative of all cirrus that can be observed from space? This could be said in a more straightforward way. Also, this is not a knock against your study -- 7 hours of in-situ sampling cannot be expected to cover the entire range of cloud variabilities.
Technical comments
- l. 408: "rangeis"
- l .441: "are hardly change"
- l. 461: "as instance" -- for instance?
- l. 475: "and and"
- l. 537: "MAS,."
- many references contain two URLs, one for the DOI (see next comment) and one that leads directly at the publisher's website. The DOI link should (in theory) always resolve to the publisher's website, so both are duplicates, and one could be omitted without loss.
- many DOI links appear as https://doi.org//https://etc (i.e. https:// appears twice). Clicking them goes to the right place, so I'm guessing this is a display issue.
Citation: https://doi.org/10.5194/egusphere-2023-112-RC2 - AC2: 'Reply on RC2', Francesco Cairo, 29 May 2023
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
| : Report abuse
-
RC1: 'Comment on egusphere-2023-112', Anonymous Referee #1, 17 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-112/egusphere-2023-112-RC1-supplement.pdf
- AC1: 'Reply on RC1', Francesco Cairo, 29 May 2023
-
RC2: 'fascinating results', Anonymous Referee #2, 24 Apr 2023
In this article, the authors present measurements performed in-situ from many airborne probes that flew within high-altitude cirrus clouds over South Asia during 7 hours over 7 flights. Among those probes, the most interesting was admittedly a backscattersonde called MAS which provided in-situ measurements in extremely close vincinity to the M55 plane (with near-zero overlap). The authors feed the Particle Size Distributions found by the in-situ probes into optical calculations to compute the Backscatter Ratio (BR) that would be observed considering a large range of possible particle Aspect Ratios (AR). By matching at each time frame the observed BR to the computed ones, the authors derive the particulate AR. Their results show it is possible to reproduce the measured BR with high fidelity and document the AR. They find that the measured BR is almost directly proportional to the ice crystal concentration. Finally, they also contrast the BR and derived particulate AR to the depolarization ratio observed in-situ by the MAS, but these efforts are frustratingly met with less success.In this paper the authors provide simultaneous in-situ and lidar-like measurements of ice crystals within cirrus clouds. This is amazing and, to my knowledge, unique. I was delighted to learn of the existence of the MAS backscattersonde. Having this kind of measurements and results (again, it's a bit hard for me to believe they do exist) published is very, very useful for people who wish to interpret lidar measurements within ice clouds. The work done and presented here is very important and useful. I share the authors' frustration with the difficulty to interprete depolarization measurements, but their results (even though inconclusive) provide important information and shed new light on the interpretation of depolarization measurements. I completely support this paper for publication. I have a few minor remarks below that the authors could take into account.
Minor comments
- l. 90 - "modelling of the optical properties of cirrus clouds is a formidable problem..." I share the authors' pain. The rest of the paragraph provides a nice review of previous efforts tackling this problem, but I'm not sure it brings a lot to the current discussion.
- section 2 -- the number of instruments is a bit large, and a table or a figure summarizing them would be nice.
- l. 132 - "the resolution is 10 s" -- I was surprised by this (relatively) very long sampling interval. It is worse than the 5 s mentioned in Cairo and al 2011. This means the MAS samples one point every 1 or 2km, which is quite a large distance. Are there ways to improve this?
- Figure 1 (1) : it is unclear to me why in Figure 1 the highest concentrations of points are not located at BR=1 ? Since clouds show up on 7 hours from the entire 35 hours of measurement, I would expect most of the points sampled by the MAS to be cloud-free, and thus to produce a BR=1 measurement. Could you please clarify my misunderstanding?
- Figure 1 (2) : could you specify in the legend the total number of data points?
- l. 158: "a negative trend with respect to temperature can be discerned" this is also reportedly the case in CALIPSO data, Sassen et al 2009 -- but I agree this trend is frustratingly hard to document quantitatively.
- In Methods : couldn't the CCP probes provide info about the particle aspect ratio? Such info could then be compared to the AR retrieved from the beta fit. Or do you think the aspect ratios from probes are too uncertain?
- l. 250: there is something wrong with the URL, I'm guessing the underscores were swallowed by the formatting system.
- l. 255: clicking the URL here brought me to the American Express website.
- l. 263-266: there is a problem with formatting here
- l. 272: missing period
- l. 371: this paragraph suddently mentions beta NC. I think this is the first time in the paper that beta NC is mentioned, and I don't think it is defined. Is beta NC the best match for the measured beta among the simulated beta AR NC ?
- Figure 3 (1): have you tried to create a scatterplot of depolarization vs AF? vs AR? of AF vs AR? Could you perhaps write the various labels of the vertical axis in the same color as their associated plot? It would make it easier to parse the figure.
- Figure 3 (2): is the AR retrieval at each time stamp completely independent from the previous retrievals? In some parts of the plot it looks like the retrievals are "stuck" at AR=3.
- Figure 3 (3): Figure 3, like most of the figures, is a bit on the small / crude side. This makes reading the figure harder than it should. Could you please produce higher-res versions of figures next time?
- Figure 3: I understand this is a bit outside the scope of the paper, but it would be very interesting to document the spatial scales over which depolarization is homogeneous.
- l. 400: "(19000s and 21000s)" what are those numbers? Can they be found somewhere on a figure? On Figure 3 times only go from 33000 to 38000.
- l. 400-405: Are the MAS/MAL depolarization ratios similarly correlated? Does the results from figure 4 suggest it is possible to use MAL measurements instead of MAS when more practical?
- Figure 4: Using a square aspect ratio in Figure 4 would make sense
- Figure 5 and 6: Having both as subplots of the same figure would help the reader. In Figure 5 I find it confusing that the y-axis says "Backscatter coefficient NIXE-CAPS" -- the NIXE-CAPS does not measure the backscatter coefficient. Same for figure 6.
- l. 419: "From the inspection of Figure 6 we can see an attempt to achieve a 1-1 correlation between the two datasets". I don't understand this sentence.
- l. 421: "the optical modelling completely fails" -- completely is perhaps a strong word, sometimes the retrieval is correct. But I agree it's perhaps worse than chance, the performance is very poor.
- l. 444 : "most of them are so called irregulars" how do you know this? Is this based on CCP imagery?
- l. 476: "We remind again that" perhaps with some editing it would be possible to avoid two reminders
- l. 477-485: This discussion is great. Based on Figure 12, wouldn't it be possible to combine the measured volume depolarization ratio and BR to retrieve the particulate/aerosol depolarization ratio (by extending the "line" these two measurements fall on all the way to the right), and use it instead of the volume depolarization ratio throughout your study? You might find better correlation with the AR time series.
- l. 490-493: It is not clear to me what is learned from Figure 13. The strong correlation between BR and Nice has already been shown before.
- Figure 15 is fascinating. Could you comment on whether particle orientation could have an effect on the volume depolarization ratio measured by the MAS, considering the specific MAS setup? Electric charging linked to lightning activity could lead to vertically-oriented particles, that would show planar faces to the MAS. Do you have any idea if the variable dynamic conditions (lines 500-504) could be disambiguated somehow by observation?
- l. 508: "a measured aspect ratio would be an obvious candidate" -- I was under the impression imagery from the CCP could provide this kind of retrieval.
- l. 579: From the start, it is not clear to me what is to be gained from following this path. Could you expand a bit on what you hoped to achieve with this?
- l. 590: "this may induce an unquantified bias in our presented statistics" -- I'm not sure I understand the point this paragraph is trying to make. Do you wish to state that the results you present here are not necessarily representative of all cirrus that can be observed from space? This could be said in a more straightforward way. Also, this is not a knock against your study -- 7 hours of in-situ sampling cannot be expected to cover the entire range of cloud variabilities.
Technical comments
- l. 408: "rangeis"
- l .441: "are hardly change"
- l. 461: "as instance" -- for instance?
- l. 475: "and and"
- l. 537: "MAS,."
- many references contain two URLs, one for the DOI (see next comment) and one that leads directly at the publisher's website. The DOI link should (in theory) always resolve to the publisher's website, so both are duplicates, and one could be omitted without loss.
- many DOI links appear as https://doi.org//https://etc (i.e. https:// appears twice). Clicking them goes to the right place, so I'm guessing this is a display issue.
Citation: https://doi.org/10.5194/egusphere-2023-112-RC2 - AC2: 'Reply on RC2', Francesco Cairo, 29 May 2023
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Francesco Cairo on behalf of the Authors (01 Jun 2023)
Author's response
Author's tracked changes
Manuscript
ED: Referee Nomination & Report Request started (03 Jul 2023) by Gabriele Stiller
RR by Anonymous Referee #2 (17 Aug 2023)
ED: Publish as is (29 Aug 2023) by Gabriele Stiller
AR by Francesco Cairo on behalf of the Authors (05 Sep 2023)
Journal article(s) based on this preprint
27 Oct 2023
A comparative analysis of in situ measurements of high-altitude cirrus in the tropics
Francesco Cairo, Martina Krämer, Armin Afchine, Guido Di Donfrancesco, Luca Di Liberto, Sergey Khaykin, Lorenza Lucaferri, Valentin Mitev, Max Port, Christian Rolf, Marcel Snels, Nicole Spelten, Ralf Weigel, and Stephan Borrmann
Atmos. Meas. Tech., 16, 4899–4925, https://doi.org/10.5194/amt-16-4899-2023, https://doi.org/10.5194/amt-16-4899-2023, 2023
Short summary
Short summary
Cirrus clouds have been observed over the Himalayan region between 10 km and the tropopause at 17–18 km. Data from backscattersonde, hygrometers, and particle cloud spectrometers have been compared to assess their consistency. Empirical relationships between optical parameters accessible with remote sensing lidars and cloud microphysical parameters (such as ice water content, particle number and surface area density, and particle aspherical fraction) have been established.
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Latest update: 30 Aug 2024
Istituto di Scienze dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, Rome, Italy
Martina Krämer
Institute of Energy and Climate Research – IEK7, Forschungszentrum Jülich, Jülich, Germany
Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
Armin Afchine
Institute of Energy and Climate Research – IEK7, Forschungszentrum Jülich, Jülich, Germany
Luca Di Liberto
Istituto di Scienze dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, Rome, Italy
Sergey Khaykin
Laboratoire Atmosphères, Observations Spatiales (LATMOS), UVSQ, Sorbonne Université, CNRS, IPSL, Guyancourt, France
Lorenza Lucaferri
Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata”, Rome, Italy
Valentin Mitev
Centre Suisse d’Electronique et de Microtechnique, Neuchâtel, Switzerland
Max Port
Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
now at: Montessori Zentrum Hofheim, Hofheim, Germany
Christian Rolf
Institute of Energy and Climate Research – IEK7, Forschungszentrum Jülich, Jülich, Germany
Marcel Snels
Istituto di Scienze dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, Rome, Italy
Nicole Spelten
Institute of Energy and Climate Research – IEK7, Forschungszentrum Jülich, Jülich, Germany
Ralf Weigel
Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
Stephan Borrmann
Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Short summary
Cirrus clouds have been observed over the Hymalaian region between 10 km and the tropopause at 17–18 km. Data from backscattersonde, hygrometers and particle cloud spectrometers have been compared to assess their consistency. Empirical relationships between optical parameters accessible with remote sensing lidars, and cloud microphysical parameters, as Ice Water Content, Particle Number and Surface Area Density, and particle aspherical fraction, have been established.
Cirrus clouds have been observed over the Hymalaian region between 10 km and the tropopause at...