the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 20 May 2025
Inversion of vertical mass concentration of non-spherical aerosols using multi-wavelength lidar
Abstract. A method of inversion the vertical mass concentration of non-spherical aerosols is proposed in this paper and the effect of particle shape, complex refraction index and wavelength on the inversion is investigated. The experiment of multi-wavelength polarized lidar indicates that the aerosols with depolarization ratios of 0.22–0.37 have non-spherical characteristics. Given the non-spherical character of dust aerosols, the optical properties with different shapes, wavelengths, and complex refraction index are calculated using discrete dipole approximation. Based on previous studies, dust aerosol particles were assumed to be ellipsoidal and rectangular in this study. In several non-spherical shapes we studied, it found that when the shape parameter of non-spherical particles is D=1 rectangular, the mass concentration difference between non-spherical and spherical aerosol is the largest, and the maximum difference can reach 19.08 %. It was found that in the detection of aerosol mass concentration by multi-wavelength lidar, the larger the wavelength, the smaller the aerosol mass concentration. It was also found that the larger the real part of the complex refraction index, the smaller the mass concentration and the smaller the maximum difference between the three wavelengths. The vertical mass concentrations inversed using this method are 2.83 mg/m3, 2.51 mg/m3, and 4.2 mg/m3 at 2:03, 7:28, and 12:36 on March 16, 2021, at the altitude of 1.5 km respectively. The inverted vertical mass concentrations were compared with the near-ground monitored at the observatory. The results show that there is same correspondence between the changes in aerosol mass concentrations near the ground and at high altitudes at the same moment.
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Status: closed (peer review stopped)
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CC1: 'Comment on egusphere-2025-401', Tetiana Kalinichenko, 21 May 2025
Dear Authors,
My name is Tetiana Kalinichenko, and I have carefully read your article "Inversion of vertical mass concentration of non-spherical aerosols using multi-wavelength lidar." I truly appreciate your valuable contribution to atmospheric science.
I would like to kindly ask for clarification regarding the measurement units used in your study:
-
What unit of "aerozol density of dust" was used in your calculations? Please check 119-120 rows. I just inspected reference (Li
et al., 2021) and didn't find it. -
Am I correct in understanding that the dust mass concentration is expressed in mg/m³? Many environmental and health-related studies commonly use μg/m³, so I would appreciate confirmation to ensure accurate interpretation and comparison with other data sources.
- I didn't find Equiation 9.
Thank you in advance for your time and assistance. Your clarification will help me better understand and align your findings with international standards.
Sincerely,
Tetiana Kalinichenko
Citation: https://doi.org/10.5194/egusphere-2025-401-CC1 -
CC2: 'Reply on CC1', H. Zhao, 26 May 2025
Dear Professor Tetiana Kalinichenko,
Thank you very much. The suggestions you gave me for my article are very good and I have benefited a lot from them. I'm very glad to answer the questions you raised. The answers to each question are as follows:
- What unit of "aerozol density of dust" was used in your calculations? Please check 119-120 rows. I just inspected reference (Li et al., 2021) and didn't find it.
Answer: I'm very sorry. Due to my negligence, I wrote the unit as μm/m ³ and the references provided were also inappropriate, which caused you a misunderstanding. The unit of the density of dust aerosol in my article is g/cm ³, which has been verified in the following two references. I will cite these two references. In both of these two literatures, the unit of dust aerosol density is used as g/cm ³.
Reference1: Veselovskii, I., Barchunov, B., et al.: Retrieval and analysis of the composition of an aerosol mixture through Mie–Raman–fluorescence lidar observations, Atmospheric Measurement Techniques, 17: 4137-4152, doi: 10.5194/amt-17-4137-2024, 2024.
Download：https://amt.copernicus.org/articles/17/4137/2024/amt-17-4137-2024.pdf
Reference2: Ansmann, A., Seifert, P., Tesche, M., Wandinger, U.: Profiling of fine and coarse particle mass: case studies of Saharan dust and Eyjafjallajokull/Grimsvotn volcanic plumes, Atmos. Chem. Phys., 12: 9399-9415, https://doi.org/10.5194/acp-12-9399-2012, 2012.
Download：https://www.researchgate.net/publication/258564791_Profiling_of_fine_and_coarse_particle_mass_case_studies_of_Saharan_dust_and_EyjafjallajokullGrimsvotn_volcanic_plumes
- Am I correct in understanding that the dust mass concentration is expressed in mg/m³? Many environmental and health-related studies commonly use μg/m³, so I would appreciate confirmation to ensure accurate interpretation and comparison with other data sources.
Answer: Thank you for your very good suggestion. Your understanding is correct. In this article, the mass concentration of dust is expressed in mg/m³. This paper studied the mass concentration of dust aerosol during a strong dust storm in March 2021 in Yinchuan. Therefore, the mass concentration was relatively high this time, and thus the unit of mass concentration, mg/m³, was used. You're right. The commonly used unit for aerosol mass concentration is μg/m³. In this paper, mg/m³ is used. This shows that during a sandstorm, the mass concentration of dust aerosols in the atmosphere is many times higher than usual.
- I didn't find Equiation 9.
Answer: Thank you for your very good suggestion. I carefully checked the paper. It was my mistake. It should be Formula 8 (200 rows).
Sincerely,
Hu Zhao
-
- RC1: 'Comment on egusphere-2025-401', Anonymous Referee #1, 22 Jun 2025
-
RC2: 'Comment on egusphere-2025-401', Anonymous Referee #2, 31 Jul 2025
This study employs the Discrete Dipole Approximation (DDA) method to determine the extinction factors of dust particles under varying input parameters, from which the dust extinction coefficients and mass concentrations are subsequently derived. The primary concern arises during the calibration of the depolarization ratio and the validation of the results. The background value, attributable to Rayleigh scattering, is seemly approximately 0.1, which exceeds the expected level. This discrepancy indicates that the authors need to conduct a more thorough examination of the lidar system, as it can severely bias the transformation of extinction coefficients and mass concentrations. The writing in the entire manuscript needs to be enhanced for readability and to prevent any potential misunderstandings. Here are my detailed comments and suggestions.
1) The DDA method has been utilized to compute the light scattering properties of ellipsoidal and rectangular particles, with a total of 63461 dipoles employed in the calculations. However, when using software like DDSCAT or ADDA to model particles with radii exceeding 2 microns, the number of dipoles currently adopted is insufficient, potentially leading to substantial computational inaccuracies. The authors are encouraged to provide a well-reasoned explanation for this limitation.
2) Figure 3 illustrates the profiles of the extinction coefficient and depolarization ratio. However, it is important to note that the data range from 0 to 1.6 km is invalid due to the field-of-view. The authors are encouraged to clearly indicate this specific height range directly on the figure to avoid potential confusion. Furthermore, the maximum detection range of the system, which is closely tied to the signal-to-noise ratio, should be explicitly defined to provide a clearer understanding of the system's limitations. In Figure 3, an interesting observation arises: the depolarization ratio exceeds 0.2 within the altitude range of 1.6 to 7.5 km, while the extinction coefficient is nearly zero above 6.5 km. The authors should provide a detailed explanation for this phenomenon, as it could significantly impact the interpretation of the results.
3) Figure 4 presents simulation results corresponding to a size parameter x=15, which translates to a particle radius of 0.8 microns. To ensure broader applicability and accuracy, it is advisable to extend simulations to cover an effective radius range of at least 0–3 microns. This adjustment would enhance the robustness and reliability of the findings.
4) Since the returned lidar signal was influenced by the field-of-view within the range of 0 to 1.6 km, Figure 5 and the subsequent figures should commence from at least 1.6 km in altitude.
5) In figure 5, the authors assigned a fixed refractive index of 1.51+0.002i for dust particles across three distinct wavelengths. Nevertheless, it is important to note that the refractive index exhibits considerable variation as a function of wavelength. Consequently, utilizing a fixed refractive index value for all wavelengths is not advisable. Also, the explanations for the difference of these profiles are not convincible.
6) The more critical issue lies in the validation and evaluation of the retrieval results. Ground-based PM2.5 and PM10 measurements are unsuitable for both comparison and correlation analysis. This is because the measurement site is located far from the lidar's position, with significant altitude differences. Additionally, the samples were dried after collection, further complicating their direct applicability.Citation: https://doi.org/10.5194/egusphere-2025-401-RC2
Status: closed (peer review stopped)
-
CC1: 'Comment on egusphere-2025-401', Tetiana Kalinichenko, 21 May 2025
Dear Authors,
My name is Tetiana Kalinichenko, and I have carefully read your article "Inversion of vertical mass concentration of non-spherical aerosols using multi-wavelength lidar." I truly appreciate your valuable contribution to atmospheric science.
I would like to kindly ask for clarification regarding the measurement units used in your study:
-
What unit of "aerozol density of dust" was used in your calculations? Please check 119-120 rows. I just inspected reference (Li
et al., 2021) and didn't find it. -
Am I correct in understanding that the dust mass concentration is expressed in mg/m³? Many environmental and health-related studies commonly use μg/m³, so I would appreciate confirmation to ensure accurate interpretation and comparison with other data sources.
- I didn't find Equiation 9.
Thank you in advance for your time and assistance. Your clarification will help me better understand and align your findings with international standards.
Sincerely,
Tetiana Kalinichenko
Citation: https://doi.org/10.5194/egusphere-2025-401-CC1 -
CC2: 'Reply on CC1', H. Zhao, 26 May 2025
Dear Professor Tetiana Kalinichenko,
Thank you very much. The suggestions you gave me for my article are very good and I have benefited a lot from them. I'm very glad to answer the questions you raised. The answers to each question are as follows:
- What unit of "aerozol density of dust" was used in your calculations? Please check 119-120 rows. I just inspected reference (Li et al., 2021) and didn't find it.
Answer: I'm very sorry. Due to my negligence, I wrote the unit as μm/m ³ and the references provided were also inappropriate, which caused you a misunderstanding. The unit of the density of dust aerosol in my article is g/cm ³, which has been verified in the following two references. I will cite these two references. In both of these two literatures, the unit of dust aerosol density is used as g/cm ³.
Reference1: Veselovskii, I., Barchunov, B., et al.: Retrieval and analysis of the composition of an aerosol mixture through Mie–Raman–fluorescence lidar observations, Atmospheric Measurement Techniques, 17: 4137-4152, doi: 10.5194/amt-17-4137-2024, 2024.
Download：https://amt.copernicus.org/articles/17/4137/2024/amt-17-4137-2024.pdf
Reference2: Ansmann, A., Seifert, P., Tesche, M., Wandinger, U.: Profiling of fine and coarse particle mass: case studies of Saharan dust and Eyjafjallajokull/Grimsvotn volcanic plumes, Atmos. Chem. Phys., 12: 9399-9415, https://doi.org/10.5194/acp-12-9399-2012, 2012.
Download：https://www.researchgate.net/publication/258564791_Profiling_of_fine_and_coarse_particle_mass_case_studies_of_Saharan_dust_and_EyjafjallajokullGrimsvotn_volcanic_plumes
- Am I correct in understanding that the dust mass concentration is expressed in mg/m³? Many environmental and health-related studies commonly use μg/m³, so I would appreciate confirmation to ensure accurate interpretation and comparison with other data sources.
Answer: Thank you for your very good suggestion. Your understanding is correct. In this article, the mass concentration of dust is expressed in mg/m³. This paper studied the mass concentration of dust aerosol during a strong dust storm in March 2021 in Yinchuan. Therefore, the mass concentration was relatively high this time, and thus the unit of mass concentration, mg/m³, was used. You're right. The commonly used unit for aerosol mass concentration is μg/m³. In this paper, mg/m³ is used. This shows that during a sandstorm, the mass concentration of dust aerosols in the atmosphere is many times higher than usual.
- I didn't find Equiation 9.
Answer: Thank you for your very good suggestion. I carefully checked the paper. It was my mistake. It should be Formula 8 (200 rows).
Sincerely,
Hu Zhao
-
- RC1: 'Comment on egusphere-2025-401', Anonymous Referee #1, 22 Jun 2025
-
RC2: 'Comment on egusphere-2025-401', Anonymous Referee #2, 31 Jul 2025
This study employs the Discrete Dipole Approximation (DDA) method to determine the extinction factors of dust particles under varying input parameters, from which the dust extinction coefficients and mass concentrations are subsequently derived. The primary concern arises during the calibration of the depolarization ratio and the validation of the results. The background value, attributable to Rayleigh scattering, is seemly approximately 0.1, which exceeds the expected level. This discrepancy indicates that the authors need to conduct a more thorough examination of the lidar system, as it can severely bias the transformation of extinction coefficients and mass concentrations. The writing in the entire manuscript needs to be enhanced for readability and to prevent any potential misunderstandings. Here are my detailed comments and suggestions.
1) The DDA method has been utilized to compute the light scattering properties of ellipsoidal and rectangular particles, with a total of 63461 dipoles employed in the calculations. However, when using software like DDSCAT or ADDA to model particles with radii exceeding 2 microns, the number of dipoles currently adopted is insufficient, potentially leading to substantial computational inaccuracies. The authors are encouraged to provide a well-reasoned explanation for this limitation.
2) Figure 3 illustrates the profiles of the extinction coefficient and depolarization ratio. However, it is important to note that the data range from 0 to 1.6 km is invalid due to the field-of-view. The authors are encouraged to clearly indicate this specific height range directly on the figure to avoid potential confusion. Furthermore, the maximum detection range of the system, which is closely tied to the signal-to-noise ratio, should be explicitly defined to provide a clearer understanding of the system's limitations. In Figure 3, an interesting observation arises: the depolarization ratio exceeds 0.2 within the altitude range of 1.6 to 7.5 km, while the extinction coefficient is nearly zero above 6.5 km. The authors should provide a detailed explanation for this phenomenon, as it could significantly impact the interpretation of the results.
3) Figure 4 presents simulation results corresponding to a size parameter x=15, which translates to a particle radius of 0.8 microns. To ensure broader applicability and accuracy, it is advisable to extend simulations to cover an effective radius range of at least 0–3 microns. This adjustment would enhance the robustness and reliability of the findings.
4) Since the returned lidar signal was influenced by the field-of-view within the range of 0 to 1.6 km, Figure 5 and the subsequent figures should commence from at least 1.6 km in altitude.
5) In figure 5, the authors assigned a fixed refractive index of 1.51+0.002i for dust particles across three distinct wavelengths. Nevertheless, it is important to note that the refractive index exhibits considerable variation as a function of wavelength. Consequently, utilizing a fixed refractive index value for all wavelengths is not advisable. Also, the explanations for the difference of these profiles are not convincible.
6) The more critical issue lies in the validation and evaluation of the retrieval results. Ground-based PM2.5 and PM10 measurements are unsuitable for both comparison and correlation analysis. This is because the measurement site is located far from the lidar's position, with significant altitude differences. Additionally, the samples were dried after collection, further complicating their direct applicability.Citation: https://doi.org/10.5194/egusphere-2025-401-RC2
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