the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Sep 2024
Shortwave Radiative Impacts of the Asian Tropopause Aerosol Layer (ATAL) using Balloon-borne In-situ measurements at three distinct locations in India
Abstract. The recurring presence of the Asian Tropopause Aerosol Layer (ATAL) in the Upper Troposphere Lower Stratosphere (UTLS) region, strongly linked with the Asian Summer Monsoon Anticyclone (ASMA), has garnered significant attention over the past decade. However, despite advances in instrumentation, studies quantifying the radiative impacts of ATAL aerosols in terms of radiative forcing and heating rates remain limited. This study aims to address this gap by evaluating the direct radiative effects of ATAL aerosols in the UTLS using in-situ measurements from the Balloon measurement of the Asian Tropopause Aerosol Layer (BATAL) campaigns conducted between 2014 and 2019 over three distinct locations in India: Gadanki (13.48° N, 79.18° E), Hyderabad (17.47° N, 78.58° E), and Varanasi (25.27° N, 82.99° E). The study considers three scenarios where UTLS aerosols are predominantly composed of sulfates, nitrates, or anthropogenic aerosols. Our findings reveal significant changes in aerosol radiative forcing, ranging from -0.015 to 0.03 Wm-2 at the top of the atmosphere, -0.01 Wm-2 to -0.16 Wm-2 at the surface, and 0 to 0.19 Wm-2 within the atmospheric column when transitioning from sulfate to nitrate and anthropogenic aerosol scenarios. UTLS aerosols were found to contribute 0.1 % to 2.3 % of the total columnar atmospheric forcing, with the highest contributions observed under the anthropogenic scenario. Notably, heating rate profiles indicate enhanced aerosol heating under anthropogenic scenarios, with rates reaching up to 0.03 K day-1, particularly over Varanasi, compared to significantly lower rates under sulfate and nitrate scenarios. The study highlights the spatial variability in radiative impacts across different locations, reflecting the structural and dynamic complexities of ATAL within the ASMA region. It emphasizes the need for a comprehensive approach combining in-situ, satellite, and model-based retrievals to overcome current limitations and achieve a more accurate understanding of the net radiative impacts of ATAL aerosols.
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Notice on discussion status
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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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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(876 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Review of “Shortwave Radiative Impacts of the Asian Tropopause Aerosol Layer (ATAL) using Balloon-borne In-situ measurements at three distinct locations in India” by Santhosh et al. (2024)', Anonymous Referee #1, 15 Nov 2024
General Comments:
The goal of this study is to evaluate the direct radiative impacts of the Asian Tropopause Aerosol Layer (ATAL) aerosols in the upper troposphere and lower stratosphere (UTLS) using in-situ measurements from the Balloon measurement of the Asian Tropopause Aerosol Layer (BATAL) campaigns (2014-2019). Detailed analyses of various aspects of the aerosol radiative forcings are presented using extensive sources of measurements and methods. I think this work will have significant contributions to the wide scientific community. I have four major comments in addition to various technical comments for the authors might take into consideration.
-Extensive analyses with various measurements and complicated methodology are presented in this work. The goal of this study should be mentioned clearly along with what the new findings are and why this work is important in the scientific community. In many places, the results are compared with previous studies without emphasizing the unique value of the results presented in this work.
-This study considers three scenarios where UTLS aerosols are predominantly composed of sulfates, nitrates, or anthropogenic aerosols. I am not sure if this is a new approach or has been used in the past. There are detailed explanations about this approach throughout the manuscript, but it is unclear if this method is new to this work or not.
-This work needs more focus. In addition to in-situ measurements, sources including reanalysis (MERRA-2) and a model (HYSPLIT) are also used. It is useful to include many data sources and results from them, but it makes it somewhat harder to focus on the main point of this study.
-Some part of the manuscript includes general statement about the impacts on climate without solid evidence. Reducing those statements would make this study concise and therefore easier to read.
Specific Comments:
L14 (Abstract) - The abstract does not include all the important findings in this work. It needs to emphasize what the new results are without explaining the background information in abstract.
L42 – Needs a reference (references) at the end of the sentence.
L47 - Add more recent references on the Asian monsoon pollution, e.g., von Hobe et al. (2021, ACP).
L52- Add more specific information about how the ATAL impacts earth’s radiative balance based on previous studies, as it is the focus of this paper.
L58 – What do ‘simulations’ mean? Please specify (e.g., global, regional, or trajectory model simulations).
L72 – A brief explanation about what the secondary aerosol formation would be helpful here.
L80 – What does ‘Influence the extinction’ mean? Did it increase or decrease the extinction?
L93- What is ‘STP’?
L100-101 – It would be useful to explain what the complexity of retrieving the aerosol properties are here.
L104 – Is the negative radiative forcing due to scattering by the aerosols?
L108 – Replace ‘simulations with’ to ‘the’.
L111 – Why does the incoming solar radiation increase at the TOA?
L113 – Is there a citation for the changes in surface temperature?
L120 – research aspects -> research questions
L163 – What is the maximum altitude of the measurements?
L175-191 – It is not easy to understand the differences in water vapor and ozone between different measurement locations. The exact values might not be needed here. I am also wondering why ozone and water vapor measurements are included in this work.
L192–199- This paragraph might not necessary here. Without including the details, I do not see much relevance to this work.
L231 – What is the cluster analysis? I think it is important to identify the types of aerosols over these locations and yet, this sentence is too brief to understand the processes.
L232- What does a.m.s.l stand for?
L243 (methodology section, section 4.1) – Is the methodology used in this work is unique and has never been used before?
L290-291- Please explain what ARF and HR are here.
L306 –Does this assumption of three aerosol types (or scenarios) represent all the aerosol types?
L328- It is unclear what ‘which is just beyond the sulfates’ means.
L368-What do the numbers in different colors in Fig. 5 mean?
L431- ‘from 13km to 19km’.
L434-It looks like the increase in aerosols is evident between 16-18 km.
L448-449-This suggests that the aerosol layer seems shallower than the 13-19 km rather than the complexity in my opinion.
L450 (section 5.2)-This section suggests that the results in this study are consistent with previous studies. What is new and different in the results presented in this work that were not known previously?
L500-504 – What do the differences in the estimated radiative forcing mean? Are those significant differences?
L526 – Need a reference for the radiative forcing from increase CO2.
L551-552 – A reference is need for the -2-32 Wm-2 surface forcing per unit AOD here.
L569 – Citation is needed after “various researchers”.
L574-577- It is not clear what the message is in these sentences.
L624-631-Are ATAL and EALs separate phenomena? I am not sure what the purpose of introducing EALs here is.
Citation: https://doi.org/10.5194/egusphere-2024-2861-RC1 - AC2: 'Reply on RC1', Bomidi Lakshmi Madhavan, 04 Apr 2025
-
RC2: 'Comment on egusphere-2024-2861', Anonymous Referee #2, 12 Jan 2025
General Comments:
The paper provides a comprehensive review of the key findings related to the Asian Tropopause Aerosol Layer (ATAL). It utilizes data from balloon measurements conducted at three different locations in India to construct mean profiles of aerosol backscatter, water vapor, ozone, and other parameters for the UTLS region. Additionally, the authors present and discuss the computed radiative forcings and heating rates based on three different aerosol scenarios for ATAL. Overall, the paper serves as a valuable review of the ATAL observed over the Indian region, although it is important to note that the full extent of ATAL is much broader.
Specific Comments:
The major limitation of this study is the lack of detailed information on the size-resolved chemical composition of the ATAL. In the absence of this data, the authors propose three scenarios—sulfates, nitrates, and anthropogenic particles—to represent the composition of ATAL and calculate the corresponding radiative forcing and heating rates. Previous studies have investigated the radiative forcing of ATAL aerosols, focusing on components such as organic carbon, black carbon, and sulfates. However, in reality, ATAL is a mixture of all these aerosol types, and its composition varies from the outer to the central regions. Therefore, characterizing ATAL simply as consisting of nitrates, sulfates, or anthropogenic particles, as done in the present study, oversimplifies the actual complexity of its composition and the obtained radiative forcing and heating rates can be far from reality.
Technical corrections:
L46: The geographic area of the ATAL is described as 10 to 40 deg N and 10 to 140 deg E in page 2 line 46 and in Fig 1 caption it is shown as 15 to 40 deg N and 15 to 105 deg E, whereas Gadanki is at 13.5 deg N which is however shown within the red box in the figure.
L 131: it is mentioned that “These campaigns involved over a hundred balloon flights..” whereas Table 1 shows a total of 21 flights.
Fig 4: ASY for nitrate shows a dip at 100% RH which is difficult to comprehend.
L 181-184: It is mentioned that the measured water vapour values over Varanasi are higher than that over Hyderabad and Gadanki. However, it is difficult to appreciate this fact in Figure 2c, unless log scale is used for the concentration values.
Table 2: Aerosol types within boundary layer for Varanasi, Urban (60%) and Continental Average (20%) doesn’t add to 100%.
L 431: “13 km to 19 km” repeated twice.
Equ 16: Since DARFx is the difference between relatively two large numbers it can be within the uncertainty of the computed ARF.
Citation: https://doi.org/10.5194/egusphere-2024-2861-RC2 - AC1: 'Reply on RC2', Bomidi Lakshmi Madhavan, 04 Apr 2025
Interactive discussion
Status: closed
-
RC1: 'Review of “Shortwave Radiative Impacts of the Asian Tropopause Aerosol Layer (ATAL) using Balloon-borne In-situ measurements at three distinct locations in India” by Santhosh et al. (2024)', Anonymous Referee #1, 15 Nov 2024
General Comments:
The goal of this study is to evaluate the direct radiative impacts of the Asian Tropopause Aerosol Layer (ATAL) aerosols in the upper troposphere and lower stratosphere (UTLS) using in-situ measurements from the Balloon measurement of the Asian Tropopause Aerosol Layer (BATAL) campaigns (2014-2019). Detailed analyses of various aspects of the aerosol radiative forcings are presented using extensive sources of measurements and methods. I think this work will have significant contributions to the wide scientific community. I have four major comments in addition to various technical comments for the authors might take into consideration.
-Extensive analyses with various measurements and complicated methodology are presented in this work. The goal of this study should be mentioned clearly along with what the new findings are and why this work is important in the scientific community. In many places, the results are compared with previous studies without emphasizing the unique value of the results presented in this work.
-This study considers three scenarios where UTLS aerosols are predominantly composed of sulfates, nitrates, or anthropogenic aerosols. I am not sure if this is a new approach or has been used in the past. There are detailed explanations about this approach throughout the manuscript, but it is unclear if this method is new to this work or not.
-This work needs more focus. In addition to in-situ measurements, sources including reanalysis (MERRA-2) and a model (HYSPLIT) are also used. It is useful to include many data sources and results from them, but it makes it somewhat harder to focus on the main point of this study.
-Some part of the manuscript includes general statement about the impacts on climate without solid evidence. Reducing those statements would make this study concise and therefore easier to read.
Specific Comments:
L14 (Abstract) - The abstract does not include all the important findings in this work. It needs to emphasize what the new results are without explaining the background information in abstract.
L42 – Needs a reference (references) at the end of the sentence.
L47 - Add more recent references on the Asian monsoon pollution, e.g., von Hobe et al. (2021, ACP).
L52- Add more specific information about how the ATAL impacts earth’s radiative balance based on previous studies, as it is the focus of this paper.
L58 – What do ‘simulations’ mean? Please specify (e.g., global, regional, or trajectory model simulations).
L72 – A brief explanation about what the secondary aerosol formation would be helpful here.
L80 – What does ‘Influence the extinction’ mean? Did it increase or decrease the extinction?
L93- What is ‘STP’?
L100-101 – It would be useful to explain what the complexity of retrieving the aerosol properties are here.
L104 – Is the negative radiative forcing due to scattering by the aerosols?
L108 – Replace ‘simulations with’ to ‘the’.
L111 – Why does the incoming solar radiation increase at the TOA?
L113 – Is there a citation for the changes in surface temperature?
L120 – research aspects -> research questions
L163 – What is the maximum altitude of the measurements?
L175-191 – It is not easy to understand the differences in water vapor and ozone between different measurement locations. The exact values might not be needed here. I am also wondering why ozone and water vapor measurements are included in this work.
L192–199- This paragraph might not necessary here. Without including the details, I do not see much relevance to this work.
L231 – What is the cluster analysis? I think it is important to identify the types of aerosols over these locations and yet, this sentence is too brief to understand the processes.
L232- What does a.m.s.l stand for?
L243 (methodology section, section 4.1) – Is the methodology used in this work is unique and has never been used before?
L290-291- Please explain what ARF and HR are here.
L306 –Does this assumption of three aerosol types (or scenarios) represent all the aerosol types?
L328- It is unclear what ‘which is just beyond the sulfates’ means.
L368-What do the numbers in different colors in Fig. 5 mean?
L431- ‘from 13km to 19km’.
L434-It looks like the increase in aerosols is evident between 16-18 km.
L448-449-This suggests that the aerosol layer seems shallower than the 13-19 km rather than the complexity in my opinion.
L450 (section 5.2)-This section suggests that the results in this study are consistent with previous studies. What is new and different in the results presented in this work that were not known previously?
L500-504 – What do the differences in the estimated radiative forcing mean? Are those significant differences?
L526 – Need a reference for the radiative forcing from increase CO2.
L551-552 – A reference is need for the -2-32 Wm-2 surface forcing per unit AOD here.
L569 – Citation is needed after “various researchers”.
L574-577- It is not clear what the message is in these sentences.
L624-631-Are ATAL and EALs separate phenomena? I am not sure what the purpose of introducing EALs here is.
Citation: https://doi.org/10.5194/egusphere-2024-2861-RC1 - AC2: 'Reply on RC1', Bomidi Lakshmi Madhavan, 04 Apr 2025
-
RC2: 'Comment on egusphere-2024-2861', Anonymous Referee #2, 12 Jan 2025
General Comments:
The paper provides a comprehensive review of the key findings related to the Asian Tropopause Aerosol Layer (ATAL). It utilizes data from balloon measurements conducted at three different locations in India to construct mean profiles of aerosol backscatter, water vapor, ozone, and other parameters for the UTLS region. Additionally, the authors present and discuss the computed radiative forcings and heating rates based on three different aerosol scenarios for ATAL. Overall, the paper serves as a valuable review of the ATAL observed over the Indian region, although it is important to note that the full extent of ATAL is much broader.
Specific Comments:
The major limitation of this study is the lack of detailed information on the size-resolved chemical composition of the ATAL. In the absence of this data, the authors propose three scenarios—sulfates, nitrates, and anthropogenic particles—to represent the composition of ATAL and calculate the corresponding radiative forcing and heating rates. Previous studies have investigated the radiative forcing of ATAL aerosols, focusing on components such as organic carbon, black carbon, and sulfates. However, in reality, ATAL is a mixture of all these aerosol types, and its composition varies from the outer to the central regions. Therefore, characterizing ATAL simply as consisting of nitrates, sulfates, or anthropogenic particles, as done in the present study, oversimplifies the actual complexity of its composition and the obtained radiative forcing and heating rates can be far from reality.
Technical corrections:
L46: The geographic area of the ATAL is described as 10 to 40 deg N and 10 to 140 deg E in page 2 line 46 and in Fig 1 caption it is shown as 15 to 40 deg N and 15 to 105 deg E, whereas Gadanki is at 13.5 deg N which is however shown within the red box in the figure.
L 131: it is mentioned that “These campaigns involved over a hundred balloon flights..” whereas Table 1 shows a total of 21 flights.
Fig 4: ASY for nitrate shows a dip at 100% RH which is difficult to comprehend.
L 181-184: It is mentioned that the measured water vapour values over Varanasi are higher than that over Hyderabad and Gadanki. However, it is difficult to appreciate this fact in Figure 2c, unless log scale is used for the concentration values.
Table 2: Aerosol types within boundary layer for Varanasi, Urban (60%) and Continental Average (20%) doesn’t add to 100%.
L 431: “13 km to 19 km” repeated twice.
Equ 16: Since DARFx is the difference between relatively two large numbers it can be within the uncertainty of the computed ARF.
Citation: https://doi.org/10.5194/egusphere-2024-2861-RC2 - AC1: 'Reply on RC2', Bomidi Lakshmi Madhavan, 04 Apr 2025
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Vadassery Neelamana Santhosh
Bomidi Lakshmi Madhavan
Sivan Thankamani Akhil Raj
Madineni Venkat Ratnam
Jean-Paul Vernier
Frank Gunther Wienhold
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2537 KB) - Metadata XML
-
Supplement
(876 KB) - BibTeX
- EndNote
- Final revised paper