the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Combined sun-photometer/lidar inversion: lessons learned during the EARLINET/ACTRIS COVID-19 Campaign
Anna Gialitaki
Marco Di Paolantonio
Davide Dionisi
Gian Luigi Liberti
Alnilam Fernandes
Artur Szkop
Aleksander Pietruczuk
Daniel Pérez-Ramírez
Maria J. Granados Muñoz
Juan Luis Guerrero-Rascado
Lucas Alados-Arboledas
Diego Bermejo-Pantaleón
Juan Antonio Bravo-Aranda
Anna Kampouri
Eleni Marinou
Vassilis Amiridis
Michael Sicard
Adolfo Comerón
Constantino Muñoz-Porcar
Alejandro Rodríguez-Gómez
Salvatore Romano
Maria Rita Perrone
Xiaoxia Shang
Mika Komppula
Rodanthi-Elisavet Mamouri
Argyro Nisantzi
Diofantos Hadjimitsis
Francisco Navas-Guzmán
Alexander Haefele
Dominika Szczepanik
Artur Tomczak
Iwona Stachlewska
Livio Belegante
Doina Nicolae
Kalliopi Artemis Voudouri
Dimitris Balis
Athina A. Floutsi
Holger Baars
Linda Miladi
Nicolas Pascal
Oleg Dubovik
Anton Lopatin
Abstract. The European Aerosol Research Lidar Network (EARLINET), part of the Aerosols, Clouds and Trace gases Research Infrastructure (ACTRIS), organized an intensive observational campaign in May 2020, with the objective of monitoring the atmospheric state over Europe during the COVID-19 lockdown and relaxation period. Besides the standard operational processing of the lidar data in EARLINET, for seven EARLINET sites having co-located sun-photometric observations in AERONET, a network exercise was held in order to derive profiles of the concentration and effective-column size distributions of the aerosols in the atmosphere, by applying the GRASP/GARRLiC inversion algorithm. The objective of this network exercise was to explore the possibility to identify the anthropogenic component and to monitor its spatial and temporal characteristics in the COVID-19 lockdown and relaxation period. While the number of cases are far from being statistically significant so as to provide a conclusive description of the atmospheric aerosols over Europe during this period, this network exercise was fundamental to derive a common methodology for applying GRASP/GARRLiC on a network of instruments with different characteristics. The limits of the approach are discussed, in particular the missing information close to the ground in the lidar measurements due to the instrument geometry, and the sensitivity of the GRASP/GARRLiC retrieval to the settings used, especially for cases with low AOD as the ones we show here. We found that this sensitivity is well-characterized in the GRASP/GARRLiC products, since it is included in their retrieval uncertainties.
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Alexandra Tsekeri et al.
Status: closed
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RC1: 'Comment on amt-2023-76', Anonymous Referee #1, 30 Jun 2023
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-76/amt-2023-76-RC1-supplement.pdf
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AC1: 'Reply on RC1', Alexandra Tsekeri, 18 Sep 2023
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-76/amt-2023-76-AC1-supplement.pdf
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AC1: 'Reply on RC1', Alexandra Tsekeri, 18 Sep 2023
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RC2: 'Comment on amt-2023-76', Anonymous Referee #2, 21 Aug 2023
The Authors discuss the application of the GRASP/GARRLiC synergistic algorithm to joint sun-photometer and lidar observations of the aerosol optical properties from the EARLINET/ACTRIS-19 COVID-19 campaign. While the original goal of the study was to characterize the anthropogenic component of atmospheric aerosols during and after the COVID-19 lockdown periods in Europe, the number of observations proved not sufficient for a statistically significant characterization. However, the Authors concentrate on investigating the sensitivity of the retrieval to a number of algorithmic parameters, such as the choice of the first guess and of the smoothing constraints. Whilst the study is rather focused on technical details, its results may still be of interest for people who try to perform synergistic aerosol retrievals from passive and active observations. In general, the paper is generally well written and can be published with minor revisions. Below are my (mostly minor) comments:
- L 56. In this sentence, I suggest replacing "anthropogenic" with "anthropic"
- L62-63, "is comprised by" -> consists of
- L83, remove "the" before "lidars"
- L91. "This is though" -> "However, this is"
- L161. What is the difference between "volume" and "particle" linear depolarization ratio? Can you define these quantities somewhere in the text?
- Figures 5 and 6. Consider inverting the order of the figures, and describe them more precisely in the text (e.g., "Fig. 5 show retrieved size distributions and concentration profiles for the case study etc...., and Fig. 6 shows the agreement betwen observed values of total optical depth, sky radiance and lidar signals, and the values fitted with GARRLic/GRASP).
- Does Fig. 7 add any new information to Fig. 6? If not, you may consider removing it (isn't the optimal solution already highlighted in Fig. 6?)
- L306-307. "This indicates... part of the retrieval uncertainty of the solution". Is this a general statement or does it just hold for the example you are showing?
- L330. "the information content... size distribution" -> "the information content of lidar measurements on the aerosol size distribution"
- L339. Some references are missing here. Are you maybe referring to Fig. 10?
- L340, eq. 1-2, Appendix B. Why do you indicate concentration with VD? Could you use a more intuitive symbol? For example, in eq. 3 you use c...
- L369-372. "h_a (pink)... full overlap height". What do you mean by "taking into account"? How do you actually take those values into account?
- Figs. 14.-15. How do the variables that appear in the plot correlate? Scatter plots may be useful in addition to histograms.
- L426. "depends also" -> "also depends"
- L460. "of the simulated signals against the input ones" -> "between simulated and measured signals"
- L462, "to obtain a quantitative metric" -> "to obtain such a metric", "input" -> "measured" ?
Citation: https://doi.org/10.5194/amt-2023-76-RC2 -
AC2: 'Reply on RC2', Alexandra Tsekeri, 18 Sep 2023
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-76/amt-2023-76-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Alexandra Tsekeri, 18 Sep 2023
Status: closed
-
RC1: 'Comment on amt-2023-76', Anonymous Referee #1, 30 Jun 2023
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-76/amt-2023-76-RC1-supplement.pdf
-
AC1: 'Reply on RC1', Alexandra Tsekeri, 18 Sep 2023
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-76/amt-2023-76-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Alexandra Tsekeri, 18 Sep 2023
-
RC2: 'Comment on amt-2023-76', Anonymous Referee #2, 21 Aug 2023
The Authors discuss the application of the GRASP/GARRLiC synergistic algorithm to joint sun-photometer and lidar observations of the aerosol optical properties from the EARLINET/ACTRIS-19 COVID-19 campaign. While the original goal of the study was to characterize the anthropogenic component of atmospheric aerosols during and after the COVID-19 lockdown periods in Europe, the number of observations proved not sufficient for a statistically significant characterization. However, the Authors concentrate on investigating the sensitivity of the retrieval to a number of algorithmic parameters, such as the choice of the first guess and of the smoothing constraints. Whilst the study is rather focused on technical details, its results may still be of interest for people who try to perform synergistic aerosol retrievals from passive and active observations. In general, the paper is generally well written and can be published with minor revisions. Below are my (mostly minor) comments:
- L 56. In this sentence, I suggest replacing "anthropogenic" with "anthropic"
- L62-63, "is comprised by" -> consists of
- L83, remove "the" before "lidars"
- L91. "This is though" -> "However, this is"
- L161. What is the difference between "volume" and "particle" linear depolarization ratio? Can you define these quantities somewhere in the text?
- Figures 5 and 6. Consider inverting the order of the figures, and describe them more precisely in the text (e.g., "Fig. 5 show retrieved size distributions and concentration profiles for the case study etc...., and Fig. 6 shows the agreement betwen observed values of total optical depth, sky radiance and lidar signals, and the values fitted with GARRLic/GRASP).
- Does Fig. 7 add any new information to Fig. 6? If not, you may consider removing it (isn't the optimal solution already highlighted in Fig. 6?)
- L306-307. "This indicates... part of the retrieval uncertainty of the solution". Is this a general statement or does it just hold for the example you are showing?
- L330. "the information content... size distribution" -> "the information content of lidar measurements on the aerosol size distribution"
- L339. Some references are missing here. Are you maybe referring to Fig. 10?
- L340, eq. 1-2, Appendix B. Why do you indicate concentration with VD? Could you use a more intuitive symbol? For example, in eq. 3 you use c...
- L369-372. "h_a (pink)... full overlap height". What do you mean by "taking into account"? How do you actually take those values into account?
- Figs. 14.-15. How do the variables that appear in the plot correlate? Scatter plots may be useful in addition to histograms.
- L426. "depends also" -> "also depends"
- L460. "of the simulated signals against the input ones" -> "between simulated and measured signals"
- L462, "to obtain a quantitative metric" -> "to obtain such a metric", "input" -> "measured" ?
Citation: https://doi.org/10.5194/amt-2023-76-RC2 -
AC2: 'Reply on RC2', Alexandra Tsekeri, 18 Sep 2023
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-76/amt-2023-76-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Alexandra Tsekeri, 18 Sep 2023
Alexandra Tsekeri et al.
Alexandra Tsekeri et al.
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