the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 18 May 2022
Detection of Stratospheric Air Intrusion Events From Ground-based High-resolution 10Be / 7Be by Accelerator Mass Spectrometry
Abstract. Locally rapid stratospheric air intrusions facilitate the transport of stratospheric material to the troposphere. Long-term continuous monitoring of such events by traditional techniques, such as sounding technology, is challenging. Beryllium-7 (7Be) and beryllium-10 (10Be) offer an alternative. These isotopes are formed by cosmic rays and are mainly produced in the lower stratosphere and upper troposphere. Due to their similar geochemical properties and substantial difference in half-lives favor relatively high 10Be / 7Be ratios in the stratosphere, as compared to the troposphere. Monitoring surface 10Be / 7Be ratios affords a potential means to identify stratospheric air intrusions. However, high temporal resolution 10Be / 7Be observational records must be taken and corrected for dust-borne 10Be to identify stratospheric air intrusions. In this study, we use Accelerator Mass Spectrometry to measure both 7Be and 10Be in rain and aerosol (down to ~ 200 cubic meters air) with an error of ~ 1.5 %. We correct for dust-borne 10Be using soil Al. This method provides precise measurements with daily resolution. We present annual beryllium isotopes (7Be, 10Be, and 10Be / 7Be ratio) record for the Chinese Loess Plateau that includes several regional sites. We show that for the city of Xi'an, the proportion of dust-borne (resuspended) 10Be was ~24 % in 2020/21. Our results confirm that stratospheric air intrusion events in the Loess Plateau are frequent and rapid throughout the year and are strongest in the spring (March–July), when 10Be / 7Be values were observed to increase about a factor of 3. Even in winter, weaker stratospheric air intrusion events can be detected. Calculated Δ(10Be / 7Be) values in winter suggest stratospheric ozone transport can lead to an ~25 % cumulative increase the surface ozone.
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RC1: 'Comment on acp-2022-282', Anonymous Referee #1, 23 May 2022
Review of “Detection of stratospheric air intrusion events from ground-based high-resolution 10Be/7Be by accelerator mass spectrometry” by X K Liu et al.
In this paper, the authors derive 10Be and 7Be measurements from collected aerosol and rainwater samples from 7 locations in central China. A large amount of data is presented. I will return to the question of the data coverage in my comments. The results are interesting and should be eventually published in final form, however, some details seems to be glossed over and need to be addressed.
In my view, the paper needs major revision.
- abstract, line 30-32. Here, it says that 24% of 10Be in Xi’an (XA) air was dust-borne, yet the various figures 2 and 3 show considerable variability.
- line 48 delete “hard-to-capture”. I am not sure what is meant here, but I assume you mean that it is difficult to quantify the intrusion events. Perhaps rewrite the sentence.
- line 57 “intrusions”
- line 64 replace “it is generally believed..”with “it has been suggested..”
- line 74 delete “the” before “very different”
- Line 82-87. Here, it is stated that 7Be was done by AMS. This is not correct. Some of the measurements were done by AMS. In the supplementary data and lines 166-169, it is stated that “some .. membranes were selected and ¼ of them were measured by AMS. The 7Be in the remaining ¾ filter membranes…were analyzed by high-purity germanium (HpGe) detector(s)..and analyzed a 477.6KeV..”. Maybe this was only a fraction of the samples, but please rewrite and explain what was actually done.
- Line 105-106. It is stated here that “an annual record with daily resolution” was obtained. This is most true for site XA (Xi’an) and QL (Qinling) but even there, it’s not actually daily, there are missing values.
- Section 2.1 Samples from the other sites were only measured at a few times in October 2020, Jan 2021 and April 2021.
- Section 2.3 lines 148-151 and supplement. 1-2. Here, it is stated that the “transmission after the second stripping foil” was improved to ~24%. If this is into 10Be4+, this is a remarkable improvement. Most labs get lower yields even into 3+. Also, what is the location of the second stripping foil? I assume it is after the analyzing magnet and before an ESA, but no details of the AMS setup are given. The discussion in the reference Zhang and Fu (2017) is not completely helpful. First, in that paper, the yield from Be2+ to Be3+ is given as 31% and from Be3+ to Be4+ is 3%. If some other improvement was done, it is not clear from this paper. Also, much of the paper of Zhang and Fu (2017) discusses other methods, such as using BeF3- as an injection beam. Hence, we still don’t know from the paper presented here by Liu et al. which method was used.
- Line 182-188. Here, the values from previous work on 10Be have errors, it would be good to quote them here.
- Line 234. “material”
- Line 236. I think “atmospheric movement information” isn’t a good term, please use something like “atmospheric circulation”
- Line 247. I think the accepted value of the half-life is 1.38Myr.
- Line 250. “cannot”
- Line 265 “aridity” not “dryness”
- Figures 2,3 and 4 have small font sizes and they can be hard to read. I suggest scaling up the figures in the revised version.
- Line 333-334. What are the “V” events and don’t you have meteorological data about what happened on those days at XA and QL?
- Line 402-406 restates what has already been said and can be deleted.
- Line 369. This seems to be a new subject here. It appears the authors try to argue that the ozone in the ground-based measurements at XA are not due to photochemical effects (e.g. due to pollution) and the ozone is due to stratospheric injection. This seems like a long shot, especially in a city like XA with considerable anthropogenic air quality problems, although I agree others (e.g. Langford) have assert similar effects elsewhere.
- Figure 4b. How are the data in figure 4b compared to fig. 4a? Are all the data used? 4b refers only to XA, but 4a also includes QL data.
- Line 455. “STE is an important channel…”. This sentence needs rewriting and makes little sense at present. Perhaps STE are important processes that can quickly transmit chemical material from the stratosphere into the lower atmospheric environment..”
Citation: https://doi.org/10.5194/acp-2022-282-RC1 - AC1: 'Reply on RC1', Xuke Liu, 28 Jun 2022
-
RC2: 'Comment on acp-2022-282', Anonymous Referee #2, 24 Jun 2022
Review of ACP-2022-282
“Detection of Stratospheric Air Intrusion Events From Ground-based High-resolution 10Be/7Be by Accelerator Mass Spectrometry” by Liu et al.
This paper describes the acquisition, analysis, and validation of a year-long record of the Be-10/Be-7 ratio in rainwater and air samples from the Chinese Loess Plateau, and uses these measurements to estimate the importance of stratosphere to troposphere transport (STT) in this region. The authors analyze the samples with accelerator mass spectrometry, which improves the sensitivity and reduces the sampling time to about 1 day, and use the Be-10/Be-7 ratio to decrease the impact of surface contamination. The technical aspects of the measurements appear to be thoroughly considered with considerable attention devoted to the difficult problem of correcting for the large background created by surface dust.
The details of the measurements will no doubt be of interest to some, but unfortunately the study really doesn’t tell us anything new about STT or atmospheric processes in general and is therefore not suitable for publication in ACP. The measurements confirm the well-established fact that STT occurs year-round with a peak in the spring at northern midlatitudes, and that it occurs primarily through discrete intrusion event such as tropopause folding that occur on timescales ranging from a few hours to several days, although the sampling time of the measurements described here is still too long to tell us anything about the dynamics of specific events. It has also been established that STT is responsible for roughly half of the free tropospheric ozone budget (Royal Society, 2008), but the conclusions about surface ozone presented here are not directly supported by the Be-10/Be-7 measurements.
Royal Society (2008), Ground-level ozone in the 21st century: future trends, impacts and policy implications, 148 pp.
Citation: https://doi.org/10.5194/acp-2022-282-RC2 -
AC2: 'Reply on RC2', Xuke Liu, 28 Jun 2022
We would like to thank reviewer #2 for feedback on the interest and comments on our paper. First, thank the reviewers for acknowledging our work. As the reviewers put it: “The authors analyze the samples with accelerator mass spectrometry, which improves the sensitivity and reduces the sampling time to about 1 day, and use the Be-10/Be-7 ratio to decrease the impact of surface contamination. The technical aspects of the measurements appear to be thoroughly considered with considerable attention devoted to the difficult problem of correcting for the large background created by surface dust.”
We believe this work suitable for publication in the ACP. In this work, long-term observational record obtained by in field measurements of radioisotopes (7Be and 10Be) in the atmosphere and used to understand atmospheric behavior (stratospheric air intrusion). This is in line with the definition of the ACP's main subject area. At present, the acquisition of observational data for 7Be and 10Be is interfered by measurement methods and natural factors. Our work addresses this issue, as described in the manuscript abstract. The main attempt is to obtain high temporal resolution 7Be and 10Be data by accelerator mass spectrometry, and then remove the 10Be interference from resuspension dust. In this way, we obtain long-term 7Be and 10Be observational records and use them to track stratospheric air intrusion processes on the ground only, especially localized intrusion events (such as tropopause folding that occur on timescales ranging from a few hours to several days). For the findings based on this method, as we reported, stratospheric air intrusion events in the Chinese Loess Plateau are frequent and rapid throughout the year and are strongest in the spring (March-July), when 10Be/7Be values were observed to increase about a factor of 3. Even in winter, weaker stratospheric air intrusion events can be detected. Calculated Δ(10Be/7Be) values in winter suggest stratospheric ozone transport can lead to an ~25% cumulative increase the surface ozone in Xi'an on the Loess Plateau, China.
Citation: https://doi.org/10.5194/acp-2022-282-AC2
-
AC2: 'Reply on RC2', Xuke Liu, 28 Jun 2022
-
CC1: 'Comment on acp-2022-282', Yongjing Guan, 27 Jun 2022
Review of “Detection of Stratospheric Air Intrusion Events From Ground-based High-resolution 10Be/7Be by Accelerator Mass Spectrometry” by liu et al.
It is a relatively new research perspective in atmospheric environmental science to study the stratosphere-troposphere exchange by testing the cosmogenic nuclides 10Be and 7Be. In this paper, ground-based aerosol and rain samples were collected, and accelerator mass spectrometry was used to achieve a more efficient and accurate analysis of 10Be and 7Be. This provides an analytical method with higher temporal resolution and more accuracy. Compared to past 10Be/7Be aerosol samples, this is a great improvement for the analysis where 7Be is confined with gamma spectroscopy. In this way, the authors report the concentrations of 10Be and 7Be at daily intervals throughout the year at multiple observation sites on the Chinese Loess Plateau, as well as the more indicative 10Be/7Be ratio. This is a new, more complete high-resolution record of 10Be and 7Be, with detailed data that lays a solid foundation for follow-up research. Overall, this is a paper of significant research value and should be published in ACP to attract more researchers' attention to this research area. There are a few minor issues:
(1) The description of how accelerator mass spectrometry measures 7Be is not detailed enough. 7Be does not have a standard sample, how to measure it, and how to calculate it, it is not clear.
(2) The work in the article involves two regions, two samples, one year of collection and isotopic beryllium analysis. This is not the case in actual work, not every day, and part of the time data is not available and needs to be clearly described.
(3) Are suspended particles in rainwater removed prior to analysis? Why the rain sample does not contain the re-suspending dust 0.5h hours after the initiated? Both STE exchange derived and tropospheric generated 10Be are associated to air particles, not as gas, where the resuspension dust is also particles, which might be also diffused to a few thousands meters height, is there any evident showing that re-suspension particles (dust) can be removed in the first half hour rain precipitation, but not the particles that TSE originated do? Although these issues are mentioned in the manuscript, a clear description will help improve the quality of the manuscript.
Citation: https://doi.org/10.5194/acp-2022-282-CC1 - AC3: 'Reply on CC1', Xuke Liu, 28 Jun 2022
Status: closed
-
RC1: 'Comment on acp-2022-282', Anonymous Referee #1, 23 May 2022
Review of “Detection of stratospheric air intrusion events from ground-based high-resolution 10Be/7Be by accelerator mass spectrometry” by X K Liu et al.
In this paper, the authors derive 10Be and 7Be measurements from collected aerosol and rainwater samples from 7 locations in central China. A large amount of data is presented. I will return to the question of the data coverage in my comments. The results are interesting and should be eventually published in final form, however, some details seems to be glossed over and need to be addressed.
In my view, the paper needs major revision.
- abstract, line 30-32. Here, it says that 24% of 10Be in Xi’an (XA) air was dust-borne, yet the various figures 2 and 3 show considerable variability.
- line 48 delete “hard-to-capture”. I am not sure what is meant here, but I assume you mean that it is difficult to quantify the intrusion events. Perhaps rewrite the sentence.
- line 57 “intrusions”
- line 64 replace “it is generally believed..”with “it has been suggested..”
- line 74 delete “the” before “very different”
- Line 82-87. Here, it is stated that 7Be was done by AMS. This is not correct. Some of the measurements were done by AMS. In the supplementary data and lines 166-169, it is stated that “some .. membranes were selected and ¼ of them were measured by AMS. The 7Be in the remaining ¾ filter membranes…were analyzed by high-purity germanium (HpGe) detector(s)..and analyzed a 477.6KeV..”. Maybe this was only a fraction of the samples, but please rewrite and explain what was actually done.
- Line 105-106. It is stated here that “an annual record with daily resolution” was obtained. This is most true for site XA (Xi’an) and QL (Qinling) but even there, it’s not actually daily, there are missing values.
- Section 2.1 Samples from the other sites were only measured at a few times in October 2020, Jan 2021 and April 2021.
- Section 2.3 lines 148-151 and supplement. 1-2. Here, it is stated that the “transmission after the second stripping foil” was improved to ~24%. If this is into 10Be4+, this is a remarkable improvement. Most labs get lower yields even into 3+. Also, what is the location of the second stripping foil? I assume it is after the analyzing magnet and before an ESA, but no details of the AMS setup are given. The discussion in the reference Zhang and Fu (2017) is not completely helpful. First, in that paper, the yield from Be2+ to Be3+ is given as 31% and from Be3+ to Be4+ is 3%. If some other improvement was done, it is not clear from this paper. Also, much of the paper of Zhang and Fu (2017) discusses other methods, such as using BeF3- as an injection beam. Hence, we still don’t know from the paper presented here by Liu et al. which method was used.
- Line 182-188. Here, the values from previous work on 10Be have errors, it would be good to quote them here.
- Line 234. “material”
- Line 236. I think “atmospheric movement information” isn’t a good term, please use something like “atmospheric circulation”
- Line 247. I think the accepted value of the half-life is 1.38Myr.
- Line 250. “cannot”
- Line 265 “aridity” not “dryness”
- Figures 2,3 and 4 have small font sizes and they can be hard to read. I suggest scaling up the figures in the revised version.
- Line 333-334. What are the “V” events and don’t you have meteorological data about what happened on those days at XA and QL?
- Line 402-406 restates what has already been said and can be deleted.
- Line 369. This seems to be a new subject here. It appears the authors try to argue that the ozone in the ground-based measurements at XA are not due to photochemical effects (e.g. due to pollution) and the ozone is due to stratospheric injection. This seems like a long shot, especially in a city like XA with considerable anthropogenic air quality problems, although I agree others (e.g. Langford) have assert similar effects elsewhere.
- Figure 4b. How are the data in figure 4b compared to fig. 4a? Are all the data used? 4b refers only to XA, but 4a also includes QL data.
- Line 455. “STE is an important channel…”. This sentence needs rewriting and makes little sense at present. Perhaps STE are important processes that can quickly transmit chemical material from the stratosphere into the lower atmospheric environment..”
Citation: https://doi.org/10.5194/acp-2022-282-RC1 - AC1: 'Reply on RC1', Xuke Liu, 28 Jun 2022
-
RC2: 'Comment on acp-2022-282', Anonymous Referee #2, 24 Jun 2022
Review of ACP-2022-282
“Detection of Stratospheric Air Intrusion Events From Ground-based High-resolution 10Be/7Be by Accelerator Mass Spectrometry” by Liu et al.
This paper describes the acquisition, analysis, and validation of a year-long record of the Be-10/Be-7 ratio in rainwater and air samples from the Chinese Loess Plateau, and uses these measurements to estimate the importance of stratosphere to troposphere transport (STT) in this region. The authors analyze the samples with accelerator mass spectrometry, which improves the sensitivity and reduces the sampling time to about 1 day, and use the Be-10/Be-7 ratio to decrease the impact of surface contamination. The technical aspects of the measurements appear to be thoroughly considered with considerable attention devoted to the difficult problem of correcting for the large background created by surface dust.
The details of the measurements will no doubt be of interest to some, but unfortunately the study really doesn’t tell us anything new about STT or atmospheric processes in general and is therefore not suitable for publication in ACP. The measurements confirm the well-established fact that STT occurs year-round with a peak in the spring at northern midlatitudes, and that it occurs primarily through discrete intrusion event such as tropopause folding that occur on timescales ranging from a few hours to several days, although the sampling time of the measurements described here is still too long to tell us anything about the dynamics of specific events. It has also been established that STT is responsible for roughly half of the free tropospheric ozone budget (Royal Society, 2008), but the conclusions about surface ozone presented here are not directly supported by the Be-10/Be-7 measurements.
Royal Society (2008), Ground-level ozone in the 21st century: future trends, impacts and policy implications, 148 pp.
Citation: https://doi.org/10.5194/acp-2022-282-RC2 -
AC2: 'Reply on RC2', Xuke Liu, 28 Jun 2022
We would like to thank reviewer #2 for feedback on the interest and comments on our paper. First, thank the reviewers for acknowledging our work. As the reviewers put it: “The authors analyze the samples with accelerator mass spectrometry, which improves the sensitivity and reduces the sampling time to about 1 day, and use the Be-10/Be-7 ratio to decrease the impact of surface contamination. The technical aspects of the measurements appear to be thoroughly considered with considerable attention devoted to the difficult problem of correcting for the large background created by surface dust.”
We believe this work suitable for publication in the ACP. In this work, long-term observational record obtained by in field measurements of radioisotopes (7Be and 10Be) in the atmosphere and used to understand atmospheric behavior (stratospheric air intrusion). This is in line with the definition of the ACP's main subject area. At present, the acquisition of observational data for 7Be and 10Be is interfered by measurement methods and natural factors. Our work addresses this issue, as described in the manuscript abstract. The main attempt is to obtain high temporal resolution 7Be and 10Be data by accelerator mass spectrometry, and then remove the 10Be interference from resuspension dust. In this way, we obtain long-term 7Be and 10Be observational records and use them to track stratospheric air intrusion processes on the ground only, especially localized intrusion events (such as tropopause folding that occur on timescales ranging from a few hours to several days). For the findings based on this method, as we reported, stratospheric air intrusion events in the Chinese Loess Plateau are frequent and rapid throughout the year and are strongest in the spring (March-July), when 10Be/7Be values were observed to increase about a factor of 3. Even in winter, weaker stratospheric air intrusion events can be detected. Calculated Δ(10Be/7Be) values in winter suggest stratospheric ozone transport can lead to an ~25% cumulative increase the surface ozone in Xi'an on the Loess Plateau, China.
Citation: https://doi.org/10.5194/acp-2022-282-AC2
-
AC2: 'Reply on RC2', Xuke Liu, 28 Jun 2022
-
CC1: 'Comment on acp-2022-282', Yongjing Guan, 27 Jun 2022
Review of “Detection of Stratospheric Air Intrusion Events From Ground-based High-resolution 10Be/7Be by Accelerator Mass Spectrometry” by liu et al.
It is a relatively new research perspective in atmospheric environmental science to study the stratosphere-troposphere exchange by testing the cosmogenic nuclides 10Be and 7Be. In this paper, ground-based aerosol and rain samples were collected, and accelerator mass spectrometry was used to achieve a more efficient and accurate analysis of 10Be and 7Be. This provides an analytical method with higher temporal resolution and more accuracy. Compared to past 10Be/7Be aerosol samples, this is a great improvement for the analysis where 7Be is confined with gamma spectroscopy. In this way, the authors report the concentrations of 10Be and 7Be at daily intervals throughout the year at multiple observation sites on the Chinese Loess Plateau, as well as the more indicative 10Be/7Be ratio. This is a new, more complete high-resolution record of 10Be and 7Be, with detailed data that lays a solid foundation for follow-up research. Overall, this is a paper of significant research value and should be published in ACP to attract more researchers' attention to this research area. There are a few minor issues:
(1) The description of how accelerator mass spectrometry measures 7Be is not detailed enough. 7Be does not have a standard sample, how to measure it, and how to calculate it, it is not clear.
(2) The work in the article involves two regions, two samples, one year of collection and isotopic beryllium analysis. This is not the case in actual work, not every day, and part of the time data is not available and needs to be clearly described.
(3) Are suspended particles in rainwater removed prior to analysis? Why the rain sample does not contain the re-suspending dust 0.5h hours after the initiated? Both STE exchange derived and tropospheric generated 10Be are associated to air particles, not as gas, where the resuspension dust is also particles, which might be also diffused to a few thousands meters height, is there any evident showing that re-suspension particles (dust) can be removed in the first half hour rain precipitation, but not the particles that TSE originated do? Although these issues are mentioned in the manuscript, a clear description will help improve the quality of the manuscript.
Citation: https://doi.org/10.5194/acp-2022-282-CC1 - AC3: 'Reply on CC1', Xuke Liu, 28 Jun 2022
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