the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 May 2024
Vertical variability of aerosol properties and trace gases over a remote marine region: A case study over Bermuda
Abstract. Remote marine regions comprise a high fraction of Earth’s surface, but in-situ vertically-resolved measurements over these locations remain scarce. Here we use airborne data during 15 vertical spiral soundings (0.15 – 8.5 km) over Bermuda during the NASA Aerosol Cloud meTeorology Interactions over the western ATlantic Experiment (ACTIVATE) to investigate the impact of different source regions on the vertical structure of trace gases, aerosol particles, and meteorological variables over 1000 km offshore of the U.S. East Coast. Results reveal significant differences in vertical profiles of variables between three different air mass source categories (North America, Ocean, Caribbean/North Africa) identified using the HYSPLIT model: (i) the strongest/weakest pollution signature from North America/Ocean category; (ii) North American air has the highest levels of CO, CH4, submicron particle number concentration, AMS mass, and highest organic mass fraction along with smoke layers in free troposphere (FT); (iii) Ocean air has the highest relative amount of nitrate, non-sea-salt sulfate, and oxalate, which are key acidic species participating in chloride depletion; (iv) pronounced coarse aerosol signature in the FT and reduced aerosol hygroscopicity in air masses from the Caribbean/North Africa associated with dust transport; and (v) considerable vertical heterogeneity for almost all variables examined, including higher O3 and submicron particle concentrations with altitude, suggestive that the FT is a potential contributor of both constituents in the marine boundary layer. This study highlights the importance of considering air mass source origin and vertical resolution to capture aerosol and trace gas properties over remote marine areas.
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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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Preprint
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Supplement
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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
(1994 KB) - Metadata XML
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Supplement
(451 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-1065', Anonymous Referee #1, 16 May 2024
Ajayi et al report observations of trace gases, aerosol properties, and meteorological variables during 15 aircraft spirals near Bermuda in June of 2022. This study provides information on the vertical distribution of these observations at a location with a history of surface-based observations. This vertical information is unique for this area and will aid interpretation of surface and satellite-based observations. The paper mainly reports the observations, describing what they observed, without much detailed analysis or interpretation. However, this is a unique and relatively large data set that may be valuable for interpretation or reinterpretation of past and future studies in the Bermuda area, as well as for understanding satellite observations of trace gases and aerosol over the oceans. The vertical information was provided by 2 separate aircraft, one flying at higher altitudes and the other flying in spirals between 0.15 to 8 km altitude. The aircraft had multiple instruments to measure meteorological parameters, aerosol properties, and trace gas concentrations. The higher-flying aircraft deployed dropsondes to measure vertical profiles of temperature, relative humidity, and wind speed.
They categorize the different vertical soundings into three source regions using the HYSPLIT model. The three regions, North America, Ocean, and North Africa/Caribbean, identified by HYSLPIT are confirmed with the observed trace gases and aerosol chemical composition. They found considerable vertical variability in all three categories, with generally higher trace gas concentrations with increasing altitude (especially for ozone). Sub-micron particle concentrations also increased with altitude suggesting new particle formation in the free troposphere. Super-micron concentrations were highest near the surface and negligible above the boundary layer. Organics tended to dominate aerosol mass in the FT while sulfate and chloride was more important closer to the surface.
This paper is suitable for publication in ACP. This data could have comprised several papers that include a more detailed analysis of the observations. The data is high quality and will be useful for such future studies and thus warrants publication. A few minor comments to improve clarity are below.
Line 224: Is it 2-3 days or 2-3 hours? I think days but I’m not sure why “hours” is there.
The short paragraph beginning on line 272 states differences in CO2 concentrations between the MBL and FT but zero analysis is given. Are these differences significant? Are they expected? Why are they different?
Section 3.6: Remind the reader the aerosol size distribution that the AMS samples at the beginning of this section. Mean numbers are given in this section. It would be good to also state the variability in some way, such as the standard deviation of the mean.
Table 6 caption: “total mass threshold > 0.4…” Threshold for what? Is this the detection limit?
Paragraph beginning on line 509: Please provide information on the variability about the mean for the Cl/Na ratio.
Citation: https://doi.org/10.5194/egusphere-2024-1065-RC1 -
RC2: 'Comment on egusphere-2024-1065', Anonymous Referee #2, 11 Jun 2024
The manuscript "Vertical variability of aerosol properties and trace gases over a remote marine region: A case study over Bermuda" presents an analysis of airborne data collected during 15 vertical spiral soundings over Bermuda as part of the NASA ACTIVATE field campaign. The study focuses on understanding the vertical distribution of trace gases and aerosol properties from different air mass source regions (North America, Ocean, Caribbean/North Africa). The data from this paper is valuable to the community, as such vertical measurements of the marine atmosphere are rare.
I do not have any major concerns about this paper. There are some minor suggestions and comments:
- Abstract: When describing the major findings, the structure of the five bullet points is inconsistent. Some are complete sentences, while others are not. I suggest using the same sentence structure throughout.
- There are many abbreviations in this paper. I suggest summarizing them in a table for clarity.
- Based on Figure 3, the wind speed at ~8000 m is only 5-10 m/s. Why is the wind speed so low? Additionally, I recommend not using red and green to distinguish different markers as they can be difficult to differentiate for colorblind readers.
- Figure 5: What is the type of aerosol diameter used in Figure 5? Is it electrical mobility diameter or aerodynamic diameter?
- Figure 8: I suggest adding a legend to the figure to explain the color representations.
- Why does the sulfate concentration decrease with increasing altitude?
- Figure 9: How do you calculate MForangic? Sea spray contains a lot of NaCl, which is refractory material to the AMS. I suggest using AMS organic mass/PM1 to get MForangic.
Citation: https://doi.org/10.5194/egusphere-2024-1065-RC2 -
AC1: 'Comment on egusphere-2024-1065', Taiwo Ajayi, 18 Jun 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1065/egusphere-2024-1065-AC1-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-1065', Anonymous Referee #1, 16 May 2024
Ajayi et al report observations of trace gases, aerosol properties, and meteorological variables during 15 aircraft spirals near Bermuda in June of 2022. This study provides information on the vertical distribution of these observations at a location with a history of surface-based observations. This vertical information is unique for this area and will aid interpretation of surface and satellite-based observations. The paper mainly reports the observations, describing what they observed, without much detailed analysis or interpretation. However, this is a unique and relatively large data set that may be valuable for interpretation or reinterpretation of past and future studies in the Bermuda area, as well as for understanding satellite observations of trace gases and aerosol over the oceans. The vertical information was provided by 2 separate aircraft, one flying at higher altitudes and the other flying in spirals between 0.15 to 8 km altitude. The aircraft had multiple instruments to measure meteorological parameters, aerosol properties, and trace gas concentrations. The higher-flying aircraft deployed dropsondes to measure vertical profiles of temperature, relative humidity, and wind speed.
They categorize the different vertical soundings into three source regions using the HYSPLIT model. The three regions, North America, Ocean, and North Africa/Caribbean, identified by HYSLPIT are confirmed with the observed trace gases and aerosol chemical composition. They found considerable vertical variability in all three categories, with generally higher trace gas concentrations with increasing altitude (especially for ozone). Sub-micron particle concentrations also increased with altitude suggesting new particle formation in the free troposphere. Super-micron concentrations were highest near the surface and negligible above the boundary layer. Organics tended to dominate aerosol mass in the FT while sulfate and chloride was more important closer to the surface.
This paper is suitable for publication in ACP. This data could have comprised several papers that include a more detailed analysis of the observations. The data is high quality and will be useful for such future studies and thus warrants publication. A few minor comments to improve clarity are below.
Line 224: Is it 2-3 days or 2-3 hours? I think days but I’m not sure why “hours” is there.
The short paragraph beginning on line 272 states differences in CO2 concentrations between the MBL and FT but zero analysis is given. Are these differences significant? Are they expected? Why are they different?
Section 3.6: Remind the reader the aerosol size distribution that the AMS samples at the beginning of this section. Mean numbers are given in this section. It would be good to also state the variability in some way, such as the standard deviation of the mean.
Table 6 caption: “total mass threshold > 0.4…” Threshold for what? Is this the detection limit?
Paragraph beginning on line 509: Please provide information on the variability about the mean for the Cl/Na ratio.
Citation: https://doi.org/10.5194/egusphere-2024-1065-RC1 -
RC2: 'Comment on egusphere-2024-1065', Anonymous Referee #2, 11 Jun 2024
The manuscript "Vertical variability of aerosol properties and trace gases over a remote marine region: A case study over Bermuda" presents an analysis of airborne data collected during 15 vertical spiral soundings over Bermuda as part of the NASA ACTIVATE field campaign. The study focuses on understanding the vertical distribution of trace gases and aerosol properties from different air mass source regions (North America, Ocean, Caribbean/North Africa). The data from this paper is valuable to the community, as such vertical measurements of the marine atmosphere are rare.
I do not have any major concerns about this paper. There are some minor suggestions and comments:
- Abstract: When describing the major findings, the structure of the five bullet points is inconsistent. Some are complete sentences, while others are not. I suggest using the same sentence structure throughout.
- There are many abbreviations in this paper. I suggest summarizing them in a table for clarity.
- Based on Figure 3, the wind speed at ~8000 m is only 5-10 m/s. Why is the wind speed so low? Additionally, I recommend not using red and green to distinguish different markers as they can be difficult to differentiate for colorblind readers.
- Figure 5: What is the type of aerosol diameter used in Figure 5? Is it electrical mobility diameter or aerodynamic diameter?
- Figure 8: I suggest adding a legend to the figure to explain the color representations.
- Why does the sulfate concentration decrease with increasing altitude?
- Figure 9: How do you calculate MForangic? Sea spray contains a lot of NaCl, which is refractory material to the AMS. I suggest using AMS organic mass/PM1 to get MForangic.
Citation: https://doi.org/10.5194/egusphere-2024-1065-RC2 -
AC1: 'Comment on egusphere-2024-1065', Taiwo Ajayi, 18 Jun 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1065/egusphere-2024-1065-AC1-supplement.pdf
Peer review completion
Journal article(s) based on this preprint
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Taiwo Adedayo Ajayi
Yonghoon Choi
Ewan C. Crosbie
Joshua P. DiGangi
Glenn S. Diskin
Marta A. Fenn
Richard A. Ferrare
Johnathan W. Hair
Miguel Ricardo A. Hilario
Chris A. Hostetler
Simon Kirschler
Richard H. Moore
Taylor J. Shingler
Michael A. Shook
Cassidy Soloff
Kenneth L. Thornhill
Christiane Voigt
Edward L. Winstead
Luke Ziemba
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1994 KB) - Metadata XML
-
Supplement
(451 KB) - BibTeX
- EndNote
- Final revised paper