OMPS-LP Aerosol Extinction Coefficients And Their Applicability in GloSSAC

Kovilakam, Mahesh; Thomason, Larry; Verkerk, Magali; Aubry, Thomas; Knepp, Travis

doi:https://doi.org/10.5194/egusphere-2024-2409

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https://doi.org/10.5194/egusphere-2024-2409

Preprints

02 Aug 2024

| 02 Aug 2024

OMPS-LP Aerosol Extinction Coefficients And Their Applicability in GloSSAC

Mahesh Kovilakam, Larry Thomason, Magali Verkerk, Thomas Aubry, and Travis Knepp

Abstract. The Global Space-based Stratospheric Aerosol Climatology (GloSSAC) is essential for understanding and modeling the climatic impacts of stratospheric aerosols. It primarily relies on data from the Stratospheric Aerosol Gas Experiment (SAGE) satellite series, supplemented by the Optical Spectrograph and Infrared Imaging System (OSIRIS) and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). GloSSAC currently provides stratospheric aerosol extinction coefficients and aerosol optical depths at 525 and 1020 nm. With CALIPSO decommissioned and OSIRIS nearing the end of its operational life, SAGE III/ISS will soon become the sole data source for GloSSAC, but it will only be available as long as the International Space Station (ISS) is operational, around 2030. Therefore, incorporating other measurements, such as those from the Ozone Mapping and Profiler Suite limb profiler (OMPS-LP), is critical. OMPS-LP has provided continuous aerosol extinction coefficient measurements since 2012 with a retrieval algorithm developed by NASA (OMPS(NASA)). However, OMPS(NASA) has been shown to overestimate aerosol extinction coefficients, particularly after the 2022 Hunga Tonga eruption, compared to the tomographic retrieval of OMPS developed by the University of Saskatchewan (OMPS(SASK)) and SAGE III/ISS. Our analysis shows that OMPS(NASA) indeed exhibits a consistently high bias (>50 %) following large volcanic eruptions and pyrocumulonimbus plumes from intense wildfires, while OMPS(SASK) shows reasonable agreement with SAGE III/ISS between 40° S and 40° N. This overestimation by OMPS(NASA) leads to an overestimation of the aerosol effective radiative forcing (ERF) and the associated model-simulated global surface temperature response by about a factor of two.

Received: 30 Jul 2024 – Discussion started: 02 Aug 2024

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Mahesh Kovilakam, Larry Thomason, Magali Verkerk, Thomas Aubry, and Travis Knepp

Status: closed

RC1:
'Comment on egusphere-2024-2409', Anonymous Referee #1, 24 Sep 2024

General Comments:
The manuscript titled "OMPS-LP Aerosol Extinction Coefficients And Their Applicability in GloSSAC" by Kovilakam et al. evaluates and compares two different aerosol extinction coefficient products from the Ozone Mapping and Profiler Suite (OMPS) — OMPS(NASA) and OMPS(SASK) — along with other available space-based measurements (such as OSIRIS and SAGE III/ISS). The article aims to assess the performance of these products, particularly following significant stratospheric aerosol events like volcanic eruptions, and to determine the best retrieval approach for integrating OMPS data into the Global Space-based Stratospheric Aerosol Climatology (GloSSAC). Additionally, the article seeks to identify potential limitations of using these datasets for understanding future volcanic and smoke events and their impacts on climate.
Their findings help inform decisions about which aerosol data products are suitable for integration into the GloSSAC, ensuring that the climatology remains robust and reliable.The article identifies potential limitations and areas for improvement in aerosol retrieval methods, guiding future research efforts to enhance data accuracy and reliability.It is recommended for publication after considering minor suggestions.

Specific Comments:

Page 1, L14, and here after: Update any instances of "40⁰S" and "40⁰N" to "40°S" and "40°N" throughout the document to accurately represent geographical coordinates using degree symbols.
Page 9, L223, 224, Review and modify all occurrences of "2.13 x 10^-2" and similar expressions. Replace them with "2.13×10^–2", ensuring consistent use of the multiplication symbol (×) and superscript for exponents for clear scientific notation.
Page 23, L372, “overestimation of extinction coefficient poleward of 40⁰S and 40⁰N as shown in Figure 3d”. Is it in Figure 3d? It seems the OMPS(SASK) data are shown in Figure 3b.
If it is misreferenced, update it to refer to the correct figure.
And, it would be beneficial to expand on the discussion related to Figure 3, incorporating insights about the "overestimation of extinction coefficient poleward of 40°S and 40°N." This could involve explaining what the overestimation indicates and any relevant implications in this area.
Page 24, check Figure 9 for panel markings. Add labels such as (a), (b), (c), etc., to each panel if they are not already present.

Citation: https://doi.org/10.5194/egusphere-2024-2409-RC1
- AC1: 'Reply on RC1', Mahesh Kovilakam, 08 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2409/egusphere-2024-2409-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2409-AC1
RC2:
'Comment on egusphere-2024-2409', Anonymous Referee #2, 24 Sep 2024

General comments:
The manuscript presents a comprehensive comparison between aerosol extinction coefficients as derived from the OMPS-LP data set and other established data sets within the GloSSAC framework. In particular, the NASA product deriving the aerosol extinction coefficients at different wavelengths as well as a second product of the University of Saskatchewan (SASK) are utilized and compared to data from OSIRIS and SAGE III/ISS measurements. In conclusion, the OMPS-LP data exhibits a clear overestimation of the aerosol extinction coefficients compared to other data (exceeding +-20%). It becomes clear from the manuscript that the NASA product cannot be used to benefit the GloSSAC framework, while there are ambitions to improve the SASK product and extend its retrieval to further wavelengths necessary to retrieve aerosol particle size information.
The discussions of the parameters presented are all comprehensive and well described. However, they slightly lack an overarching structure which could be overcome by inserting a brief outline at the end of the introduction summarizing the following studies.
The evaluation of the effective radiative forcing and associated surface temperature response helps to bring the previously discussed features into the context of climate modelling which is addressed again in the conclusions.
Specific comments:
In Section 3.2, the aerosol extinction coefficients at various wavelengths (510, 745, 864 and 997 nm) are assessed and an inconsistent behavior is found across the spectrum. Is this effect understood (particularly the deviation of the 997 nm data from the other data)? If so, please add an explanation to the text.
Section 3.3 evaluates the usability of OMPS(NASA) data in the context of the GloSSAC framework. The comparison in this section is limited to the time period of SAGE III measurements and thus partly redundant to the previous direct comparison of OMPS(NASA) and SAGE III data. I suggest to shorten this part considerably to improve readability. This could be achieved by merging Fig. 7 and 8 and shortening the text to the necessary minimum; or moving the figures into an appendix and adding all relevant information in the text of the preceding section.
Technical corrections:
Please revise the text with special attention to the correct representation of units (e.g., usage of the degree sign °N and °S), consistent naming (e.g., the Hunga Tonga eruption instead of Tonga eruption, OMPS(SASK) instead of SASK or OMPS-SASK) and the usage of articles (e.g., the aerosol extinction coefficient).
---
l.47: stratosphere aerosol levels -> stratospheric aerosol levels
l.99: known as OMPS(SASK) -> I suggest ‘in the following referred to as OMPS(SASK)’ since this is not an official abbreviation of the data set but a naming convention within this manuscript.
l.230: ‘zonally averaged gridded data into 5 degree latitude bands’ is not completely clear to me. Please consider to extend the description of the shown parameter to enhance the understanding.
l.285: I suggest to write ’important information’ instead of ‘valuable information’ to really stress the importance of direct multi-wavelength aerosol extinction coefficient measurements.
l.306: I suggest to use ‘An important finding’ instead of ‘An important difference between these two plots’
l.374: As I understand the OMPS(NASA) ERF is – 0.73 Wm^-2at its peak while the other data are at about –0.2 Wm^-2 which means that the number is by a factor 3 lower. Please consider rewriting ‘a factor of 3 stronger’ instead of ‘higher’.
l.380 and 389: You mention the numbers for the cooling twice. Please rephrase and avoid the repetition. Also, from the text it is not completely clear if you refer to the cooling at the peak ERF (August’22) or the peak cooling (December’22).
l.433: Same as in l. 374: the ERF is ‘three times stronger’ instead of ‘higher’
---
Fig. 1: Please enlarge the legends in each plot. Please consider adapting your color scheme. I suggest to use orange for the difference of OMPS to SASK and green for the difference of OMPS to OSIRIS and so on to match with the respective SASK and OSIRIS color in the extinction plots. You may also think about renaming OMPS -> OMPS(NASA) and SASK -> OMPS(SASK) to be consistent with the text.
Fig. 2: Please ensure consistent labeling on the x-axis (60 °S to 60 °N versus -60 to +60) and add a label on the y-axis. For subplots e) to g) add the brackets (OMPS(NASA)-SASK)/SASK and again rethink consistent naming conventions.
Fig. 3 to 8: Please correct the position of the brackets and add y-axis labels (see comment above). In Fig. 6 also the color bar label is missing as well as the exact description of the shown parameter in the figure caption.
Fig. 8: You may think of adding the subplots e) and f) to Fig. 7 and skipping Fig. 8 because Fig. 8 a) to d) is just the same as Fig. 7 a) to d) with a modified time axis.
Fig. 9: Please add the panel labels a), b) and c) in the plots or refer to it as the upper, middle and lower panel in the text.

Citation: https://doi.org/10.5194/egusphere-2024-2409-RC2
- AC2: 'Reply on RC2', Mahesh Kovilakam, 08 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2409/egusphere-2024-2409-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2409-AC2

Status: closed

RC1:
'Comment on egusphere-2024-2409', Anonymous Referee #1, 24 Sep 2024

General Comments:
The manuscript titled "OMPS-LP Aerosol Extinction Coefficients And Their Applicability in GloSSAC" by Kovilakam et al. evaluates and compares two different aerosol extinction coefficient products from the Ozone Mapping and Profiler Suite (OMPS) — OMPS(NASA) and OMPS(SASK) — along with other available space-based measurements (such as OSIRIS and SAGE III/ISS). The article aims to assess the performance of these products, particularly following significant stratospheric aerosol events like volcanic eruptions, and to determine the best retrieval approach for integrating OMPS data into the Global Space-based Stratospheric Aerosol Climatology (GloSSAC). Additionally, the article seeks to identify potential limitations of using these datasets for understanding future volcanic and smoke events and their impacts on climate.
Their findings help inform decisions about which aerosol data products are suitable for integration into the GloSSAC, ensuring that the climatology remains robust and reliable.The article identifies potential limitations and areas for improvement in aerosol retrieval methods, guiding future research efforts to enhance data accuracy and reliability.It is recommended for publication after considering minor suggestions.

Specific Comments:

Page 1, L14, and here after: Update any instances of "40⁰S" and "40⁰N" to "40°S" and "40°N" throughout the document to accurately represent geographical coordinates using degree symbols.
Page 9, L223, 224, Review and modify all occurrences of "2.13 x 10^-2" and similar expressions. Replace them with "2.13×10^–2", ensuring consistent use of the multiplication symbol (×) and superscript for exponents for clear scientific notation.
Page 23, L372, “overestimation of extinction coefficient poleward of 40⁰S and 40⁰N as shown in Figure 3d”. Is it in Figure 3d? It seems the OMPS(SASK) data are shown in Figure 3b.
If it is misreferenced, update it to refer to the correct figure.
And, it would be beneficial to expand on the discussion related to Figure 3, incorporating insights about the "overestimation of extinction coefficient poleward of 40°S and 40°N." This could involve explaining what the overestimation indicates and any relevant implications in this area.
Page 24, check Figure 9 for panel markings. Add labels such as (a), (b), (c), etc., to each panel if they are not already present.

Citation: https://doi.org/10.5194/egusphere-2024-2409-RC1
- AC1: 'Reply on RC1', Mahesh Kovilakam, 08 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2409/egusphere-2024-2409-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2409-AC1
RC2:
'Comment on egusphere-2024-2409', Anonymous Referee #2, 24 Sep 2024

General comments:
The manuscript presents a comprehensive comparison between aerosol extinction coefficients as derived from the OMPS-LP data set and other established data sets within the GloSSAC framework. In particular, the NASA product deriving the aerosol extinction coefficients at different wavelengths as well as a second product of the University of Saskatchewan (SASK) are utilized and compared to data from OSIRIS and SAGE III/ISS measurements. In conclusion, the OMPS-LP data exhibits a clear overestimation of the aerosol extinction coefficients compared to other data (exceeding +-20%). It becomes clear from the manuscript that the NASA product cannot be used to benefit the GloSSAC framework, while there are ambitions to improve the SASK product and extend its retrieval to further wavelengths necessary to retrieve aerosol particle size information.
The discussions of the parameters presented are all comprehensive and well described. However, they slightly lack an overarching structure which could be overcome by inserting a brief outline at the end of the introduction summarizing the following studies.
The evaluation of the effective radiative forcing and associated surface temperature response helps to bring the previously discussed features into the context of climate modelling which is addressed again in the conclusions.
Specific comments:
In Section 3.2, the aerosol extinction coefficients at various wavelengths (510, 745, 864 and 997 nm) are assessed and an inconsistent behavior is found across the spectrum. Is this effect understood (particularly the deviation of the 997 nm data from the other data)? If so, please add an explanation to the text.
Section 3.3 evaluates the usability of OMPS(NASA) data in the context of the GloSSAC framework. The comparison in this section is limited to the time period of SAGE III measurements and thus partly redundant to the previous direct comparison of OMPS(NASA) and SAGE III data. I suggest to shorten this part considerably to improve readability. This could be achieved by merging Fig. 7 and 8 and shortening the text to the necessary minimum; or moving the figures into an appendix and adding all relevant information in the text of the preceding section.
Technical corrections:
Please revise the text with special attention to the correct representation of units (e.g., usage of the degree sign °N and °S), consistent naming (e.g., the Hunga Tonga eruption instead of Tonga eruption, OMPS(SASK) instead of SASK or OMPS-SASK) and the usage of articles (e.g., the aerosol extinction coefficient).
---
l.47: stratosphere aerosol levels -> stratospheric aerosol levels
l.99: known as OMPS(SASK) -> I suggest ‘in the following referred to as OMPS(SASK)’ since this is not an official abbreviation of the data set but a naming convention within this manuscript.
l.230: ‘zonally averaged gridded data into 5 degree latitude bands’ is not completely clear to me. Please consider to extend the description of the shown parameter to enhance the understanding.
l.285: I suggest to write ’important information’ instead of ‘valuable information’ to really stress the importance of direct multi-wavelength aerosol extinction coefficient measurements.
l.306: I suggest to use ‘An important finding’ instead of ‘An important difference between these two plots’
l.374: As I understand the OMPS(NASA) ERF is – 0.73 Wm^-2at its peak while the other data are at about –0.2 Wm^-2 which means that the number is by a factor 3 lower. Please consider rewriting ‘a factor of 3 stronger’ instead of ‘higher’.
l.380 and 389: You mention the numbers for the cooling twice. Please rephrase and avoid the repetition. Also, from the text it is not completely clear if you refer to the cooling at the peak ERF (August’22) or the peak cooling (December’22).
l.433: Same as in l. 374: the ERF is ‘three times stronger’ instead of ‘higher’
---
Fig. 1: Please enlarge the legends in each plot. Please consider adapting your color scheme. I suggest to use orange for the difference of OMPS to SASK and green for the difference of OMPS to OSIRIS and so on to match with the respective SASK and OSIRIS color in the extinction plots. You may also think about renaming OMPS -> OMPS(NASA) and SASK -> OMPS(SASK) to be consistent with the text.
Fig. 2: Please ensure consistent labeling on the x-axis (60 °S to 60 °N versus -60 to +60) and add a label on the y-axis. For subplots e) to g) add the brackets (OMPS(NASA)-SASK)/SASK and again rethink consistent naming conventions.
Fig. 3 to 8: Please correct the position of the brackets and add y-axis labels (see comment above). In Fig. 6 also the color bar label is missing as well as the exact description of the shown parameter in the figure caption.
Fig. 8: You may think of adding the subplots e) and f) to Fig. 7 and skipping Fig. 8 because Fig. 8 a) to d) is just the same as Fig. 7 a) to d) with a modified time axis.
Fig. 9: Please add the panel labels a), b) and c) in the plots or refer to it as the upper, middle and lower panel in the text.

Citation: https://doi.org/10.5194/egusphere-2024-2409-RC2
- AC2: 'Reply on RC2', Mahesh Kovilakam, 08 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2409/egusphere-2024-2409-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-2409-AC2

Mahesh Kovilakam, Larry Thomason, Magali Verkerk, Thomas Aubry, and Travis Knepp

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Short summary

The Global Space-based Stratospheric Aerosol Climatology (GloSSAC) is essential for understanding and modeling the climatic impacts of stratospheric aerosols, comprising data from various space-based measurements. Here, we examine and evaluate the Ozone Mapping and Profiler Suite limb profiler (OMPS) against other datasets, particularly SAGE III/ISS, to discern differences and explore the applicability of OMPS data within the GloSSAC framework.


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