the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Jul 2024
Measurement report: Analysis of aerosol optical depth variation at Zhongshan Station in Antarctica
Abstract. Our understanding of aerosol optical depth (AOD) in Antarctica remains limited due to the scarcity of ground observation stations and limited daylight days. Utilizing data from the CE318-T photometer spanning from January 2020 to April 2023 at Zhongshan Station, we analysed the seasonal, monthly, and diurnal variations in AOD and Ångström exponent (AE). AOD median values increased from spring (0.033) to winter (0.115), while AE peaked during summer (1.010) and autumn (1.034), declining in winter (0.381), indicating a transition in dominant aerosol particle size from fine to coarse mode between summer and winter. Monthly mean AOD variation closely paralleled the proportion of AE<1, suggesting fluctuations in coarse mode particle proportions drive AOD variation. Increases in AOD during spring and winter correlated with decreases in fine mode fraction, while increases during summer and winter related to fine mode particle growth and aging. We observed a peak in AOD (~0.06) at 14:00 local time at Zhongshan Station, possibly associated with a slight decrease in boundary layer height (BLH). Additionally, higher (lower) wind speeds corresponded to lower (higher) AOD values, indicating the diffusion (accumulation) effect. The temperature and AOD showed an insignificant positive correlation between (R = 0.22, p = 0.40), relative humidity exhibited a significant negative correlation with AOD (R = -0.59, p = 0.02). Backward trajectory analysis revealed that coarse particles from the ocean predominantly contributed to high AOD daily mean values in summer, while fine particles on low AOD days originated mainly from the air mass over the Antarctic Plateau.
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RC1: 'Comment on egusphere-2024-798', Anonymous Referee #1, 01 Aug 2024
This study is too simple and may be well-suited as a measurement report. Undoubtedly, the aerosols in that location are very important to study, but the paper lacks enough depth to it.
However, I have some minor comments
“The increase in AOD during spring and winter correlates with a reduction in the fine mode fraction, whereas the increase observed in summer and autumn may be attributed to the growth and aging of fine particles.” How can both increase? Please correct
“Increases in AOD during spring and winter correlated with decreases in fine mode fraction, while increases during summer and winter related to fine mode particle growth and aging.” This line is very confusing with the usage of ‘increase’’
The last line in abstract only talks about the origins of particles in the summer. Why specifically summer? Why not other seasons?
The abstract is incomplete. I suggest you to add a conclusion line to your abstract as to why this study is important or how it can help others?
How is DMS found in the plateau? Does it come from transportation from ocean? But you have mentioned about katabatic winds that drive from interior to coastal
“AOD675 nm is associated with the declining 𝜂”….. introduce 𝜂 before using it
Citation: https://doi.org/10.5194/egusphere-2024-798-RC1 - AC1: 'Reply on RC1', Lijing Chen, 19 Aug 2024
- AC2: 'Reply on RC1', Lijing Chen, 13 Sep 2024
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RC2: 'Comment on egusphere-2024-798', Anonymous Referee #2, 07 Sep 2024
The study offers a comprehensive analysis of AOD and AE variations at Zhongshan Station in Antarctica (where is unnoticed area in the community), providing valuable insights into seasonal and diurnal trends of these aerosol parameters. The authors have effectively utilized multiple data sources and analysis techniques to draw conclusions about the influence of meteorological factors, aerosol sources, and particle size dynamics on AOD and AE. Although the analysis looks simple, this research provide new in situ data and an important advancement on aerosol behavior in the Antarctic region, where the observation is very sparse and very hard to carry out. Thus I suggest acceptance after minor revision
Major:
1. The authors provide valuable insights into the relationship between particle size and AOD across different seasons. To strengthen the paper’s cohesiveness, it would be beneficial to elaborate on the apparent seasonal differences in AOD variations. Specifically, clarifying how fine mode particles contribute to low AOD ranges while coarse mode particles are associated with high AOD values, and how this relationship evolves across seasons, would provide a more comprehensive understanding of the complex aerosol dynamics in the Antarctic environment.
2. The study offers an intriguing analysis of the influence of wind speed on aerosol dispersal, noting that higher wind speeds generally lead to lower AOD values. However, the authors also highlight the role of blowing snow over sea ice in generating sea salt aerosols, contributing to winter peaks in sea salt aerosols. To further enrich the discussion, it would be valuable to expand on the interplay between wind speed and AOD during winter, considering both the dispersal and production of aerosols. This additional context would provide a more nuanced understanding of the complex relationships at play in this unique environment.
3. Expanding the Discussion section to elaborate on how the observed AOD and AE variations relate to radiative forcing, cloud formation, and potential impacts on snow and ice melt in Antarctica. This would strengthen the study’s significance by connecting the findings to broader climate-related processes.
4. Addressing the potential impact of missing measurements and instrument downtime on the correlation analysis of AOD and AE with meteorological variables. Quantifying measurement uncertainty and discussing its implications for the interpretation of correlation coefficients would further enhance the study’s rigor.
Minor:
1. Line 54-55, line 122, and line 314: when describing the values of AOD and AE, it is suggested to unify the number of decimal places to improve accuracy.
2. It is suggested to retain three decimal places for the values in Table 1 to ensure consistency with the number of decimal places used inthe manuscript.
3. There is an error in the reference of Figure 5 in line 224, and it is suggested to be corrected as (Fig.5).
4. Please correct the notation of Celsius (℃) in line 84 and Figure 7.
5. In Section 3.2, the authors can make a more natural transition from a discussion of high concentrations of sea salt aerosols in winter as the cause of high AOD to thediscussion of DMS and MSA in summer. It is suggested to make some adjustments to the statement.
6. When describing Figure 4, the author should explain what the parameters in the figure represent, such as and , it helps the readers understand the following analysis.
7. In Section 3.3, the authorsdiscussed the relationship between temperature and relative humidity and the diurnal variation of AOD. Is there a physical mechanism to explain the positive or negative impact of temperature and relative humidity changes on aerosol load at Zhongshan Station?
8. There are still some grammatical errors in the manuscript. Please revise carefully. For example:
Line 99-100: change “eliminate” to “eliminated” for correct tense. Change “exceeding” to “exceedingly” for correct adverb form.
Line 225-226: “from 5:00 to 12:00 to the lowest value” can be changed to “from 5:00 to 12:00, reaching the lowest value.”
Line 240: “average speeds range from 2 to 9 m s-1” should be changed to “average speeds ranging from 2 to 9 m s-1”.
Line 252: “by influencing the air convection and influences the formation” should be “by influencing the air convection and influencing the formation”.
9. Some expressions in the manuscript could be further streamlined to enhance the quality of the article.For example:
Line 126-129: The statements “The annual mean ± SD values of the AOD500 nm were 0.074±0.090, 0.051±0.066, 0.071±0.117, and 0.053±0.031 in 2020, 2021, 2022, and 2023, respectively (Table 1)” and “The annual mean ± SD values of the AE440-870 nm were 1.134±0.411, 0.953±0.338, 0.883±0.374, 0.753±0.206 in 2020, 2021, 2022, and 2023” can be combined into one sentence to reduce redundancy.
Line 270-280: “In addition to meteorological conditions that can affect the diurnal variation characteristics of AOD, we believe that aerosol sources may be another influencing factor” can be simplified to “Besides meteorological conditions, aerosol sources may also influence the diurnal variation characteristics of AOD”.
10. The summarysection should not rehash the detailed reasons for seasonal variations in AOD and AE, as these have been discussed in the results section. Simplification is recommended.
Citation: https://doi.org/10.5194/egusphere-2024-798-RC2 -
AC3: 'Reply on RC2', Lijing Chen, 30 Sep 2024
Thank you very much for your positive evaluation and comments on our research. We greatly appreciate your valuable suggestions and will carefully consider them during the revision process. Your inputs will contribute to enhancing the quality and depth of our study, particularly in the challenging context of sparse observations in the Antarctic region. Our research provides new in situ data and represents an important advancement in understanding aerosol behavior. Our detailed responses are in the supplement file.
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AC3: 'Reply on RC2', Lijing Chen, 30 Sep 2024
Data sets
Analysis of aerosol optical depth variation at Zhongshan Station in Antarctica L. Chen https://doi.org/10.5281/zenodo.10983097
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