the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Feb 2024
Does the Asian Summer Monsoon Play a Role in the Stratospheric Aerosol Budget of the Arctic?
Abstract. The southeast Asian monsoon has a strong convectional component, with which aerosols are able to be lifted up into the lower stratosphere. Due to usually long lifetimes and long-range transport aerosols remain there much longer than in the troposphere and are also able to be advected around the globe. Our aim of this study is a synergy between modelled tropical aerosol tracers by Chemical Lagrangian Model of the Stratosphere (CLaMS) and KARL (Koldewey Aerosol Raman Lidar) at AWIPEV, Ny-Ålesund in the Arctic, by comparing back- and forward trajectories with exemplary days of Lidar measurements as well as analyse the stratospheric aerosol background. We use global 3-dimensional Lagrangian transport simulations including surface origin tracers as well as back-trajectories to identify source regions of the aerosol particles measured over Ny-Ålesund. We analysed Lidar data for the year 2021 and found the stratosphere generally clear, without obvious aerosol layers from volcanic eruptions or forest fires. Still an obvious annual cycle of the backscatter coefficient with higher values in late summer to autumn and lower values in late winter have been found. Results from CLaMS model simulations indicate that from late summer to early autumn filaments with high fractions of air which originate in South Asia – one of the most polluted regions in the world – reach the Arctic in altitudes between 360 K and 380 K potential temperature. We found a coinciding measurement between the overpass of such a filament and Lidar observations, we estimated that backscatter and depolarisation increased by roughly 15 % during this event compared to the background aerosol concentration. Hence we demonstrate that the Asian summer monsoon is a weak but measurable source for Arctic stratospheric aerosol in late summer to early autumn.
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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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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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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-124', Kerstin Stebel, 24 Mar 2024
- AC2: 'Reply on RC1', Sandra Graßl, 22 Apr 2024
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RC2: 'Comment on egusphere-2024-124', Anonymous Referee #1, 29 Mar 2024
This paper discusses lidar stratospheric aerosol observations in the Arctic for the year 2021 when there were no significant events of volcanic eruptions and forest files. By combining with artificial tracer and backward trajectory calculations, the authors conclude that slight increases of lidar aerosol signals around August come from the Asian Tropopause Aerosol Layer (ATAL). At the same time, the authors describe the characteristics of ATAL originating aerosols over the Arctic region in terms of lidar variables.
I think that the methodology and data analysis are sound, and that the interpretation of the analysis results is reasonable. Therefore, the manuscript will be acceptable for publication in the Atmospheric Chemistry and Physics after considering the following comments and suggestions.
One remaining question is, what are the signals around May. While this should not be of ATAL origin and thus could be out of the scope of this research, it would be nice to have some hypotheses.
Some minor points:
The authors use both “southeast” Asian monsoon and “south” Asian monsoon through the manuscript. Probably, using only “Asian summer monsoon” would be good.
Line 103: Remove “calculations of the”
Lines 132-124: Please specify either parallel or perpendicular for “signal” (two places)
Line 241: p_0 is usually taken as 1000 hPa, rather than 1013 hPa. Probably, the choice here depends on the definition in CLaMS and trajectory calculations.
Figure 5 looks strange, because the values in January and in December should usually be similar, so that we have a seasonal “cycle”. Instead, Figure 5 shows a linearly increasing-trend component.
Line 346 and other places (e.g. line 450): The authors use the terms “aged” and “young”. Please give a rough idea of the time period for both in the context of this work.
Line 404: Aitken?
Line 472: I am afraid that I cannot see this in Figure 15. There are quite many gray curves.
Citation: https://doi.org/10.5194/egusphere-2024-124-RC2 -
AC1: 'Reply on RC2', Sandra Graßl, 16 Apr 2024
Dear anonymous referee,
thank you for reviewing the manuscript. Within your comments we added our responses within your comments.
Best regareds
Some minor points:
- The authors use both “southeast” Asian monsoon and “south” Asian monsoon through the manuscript. Probably, using only “Asian summer monsoon” would be good. => Thank you for pointing it out. We exchanged everything to "Asian summer monsoon"
- Line 103: Remove “calculations of the” => changed
- Lines 132-124: Please specify either parallel or perpendicular for “signal” (two places) => thank you for this note, I added the information that it applies to both orientations of polarisation
- Line 241: p_0 is usually taken as 1000 hPa, rather than 1013 hPa. Probably, the choice here depends on the definition in CLaMS and trajectory calculations. => Thank you for pointing it out. We have checked the difference between a potential temperature calculated with 1000hPa and 1013 hPa. The difference in height is <100m at a exemplary height of 15km
- Figure 5 looks strange, because the values in January and in December should usually be similar, so that we have a seasonal “cycle”. Instead, Figure 5 shows a linearly increasing-trend component. => Thank you for pointing this fact out. When you compare Figure 5 with Figure 10 you have for two selected altitudes also 25th and 75th percentile as well as mean and median. There you can see that December and January are different and the "gap" between December and January is within the error bars. All in all this does not effect our results of this manuscript.
- Line 346 and other places (e.g. line 450): The authors use the terms “aged” and “young”. Please give a rough idea of the time period for both in the context of this work. => In other publications (like Ohneiser et al., 2023) a clear and distinct layer was found in the Arctic stratosphere. In our case we don't have such an easy visable layer rather a faint increased backscatter coefficient, which might have originated from a distinct layer but due to several different processes this layer lost its borders.
- Line 404: Aitken? => thank you, corrected
- Line 472: I am afraid that I cannot see this in Figure 15. There are quite many gray curves. => This figure shall give an overview of a many different pathways from the Arctic to the position, where the air parcel first touches the ground, which is then marked with a coloured circle. We want to emphasize the accumulation of contact points with the boundary layer and the propagation time. The propagation paths are just an additional information about generally the back-trajectories
Citation: https://doi.org/10.5194/egusphere-2024-124-AC1
-
AC1: 'Reply on RC2', Sandra Graßl, 16 Apr 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-124', Kerstin Stebel, 24 Mar 2024
- AC2: 'Reply on RC1', Sandra Graßl, 22 Apr 2024
-
RC2: 'Comment on egusphere-2024-124', Anonymous Referee #1, 29 Mar 2024
This paper discusses lidar stratospheric aerosol observations in the Arctic for the year 2021 when there were no significant events of volcanic eruptions and forest files. By combining with artificial tracer and backward trajectory calculations, the authors conclude that slight increases of lidar aerosol signals around August come from the Asian Tropopause Aerosol Layer (ATAL). At the same time, the authors describe the characteristics of ATAL originating aerosols over the Arctic region in terms of lidar variables.
I think that the methodology and data analysis are sound, and that the interpretation of the analysis results is reasonable. Therefore, the manuscript will be acceptable for publication in the Atmospheric Chemistry and Physics after considering the following comments and suggestions.
One remaining question is, what are the signals around May. While this should not be of ATAL origin and thus could be out of the scope of this research, it would be nice to have some hypotheses.
Some minor points:
The authors use both “southeast” Asian monsoon and “south” Asian monsoon through the manuscript. Probably, using only “Asian summer monsoon” would be good.
Line 103: Remove “calculations of the”
Lines 132-124: Please specify either parallel or perpendicular for “signal” (two places)
Line 241: p_0 is usually taken as 1000 hPa, rather than 1013 hPa. Probably, the choice here depends on the definition in CLaMS and trajectory calculations.
Figure 5 looks strange, because the values in January and in December should usually be similar, so that we have a seasonal “cycle”. Instead, Figure 5 shows a linearly increasing-trend component.
Line 346 and other places (e.g. line 450): The authors use the terms “aged” and “young”. Please give a rough idea of the time period for both in the context of this work.
Line 404: Aitken?
Line 472: I am afraid that I cannot see this in Figure 15. There are quite many gray curves.
Citation: https://doi.org/10.5194/egusphere-2024-124-RC2 -
AC1: 'Reply on RC2', Sandra Graßl, 16 Apr 2024
Dear anonymous referee,
thank you for reviewing the manuscript. Within your comments we added our responses within your comments.
Best regareds
Some minor points:
- The authors use both “southeast” Asian monsoon and “south” Asian monsoon through the manuscript. Probably, using only “Asian summer monsoon” would be good. => Thank you for pointing it out. We exchanged everything to "Asian summer monsoon"
- Line 103: Remove “calculations of the” => changed
- Lines 132-124: Please specify either parallel or perpendicular for “signal” (two places) => thank you for this note, I added the information that it applies to both orientations of polarisation
- Line 241: p_0 is usually taken as 1000 hPa, rather than 1013 hPa. Probably, the choice here depends on the definition in CLaMS and trajectory calculations. => Thank you for pointing it out. We have checked the difference between a potential temperature calculated with 1000hPa and 1013 hPa. The difference in height is <100m at a exemplary height of 15km
- Figure 5 looks strange, because the values in January and in December should usually be similar, so that we have a seasonal “cycle”. Instead, Figure 5 shows a linearly increasing-trend component. => Thank you for pointing this fact out. When you compare Figure 5 with Figure 10 you have for two selected altitudes also 25th and 75th percentile as well as mean and median. There you can see that December and January are different and the "gap" between December and January is within the error bars. All in all this does not effect our results of this manuscript.
- Line 346 and other places (e.g. line 450): The authors use the terms “aged” and “young”. Please give a rough idea of the time period for both in the context of this work. => In other publications (like Ohneiser et al., 2023) a clear and distinct layer was found in the Arctic stratosphere. In our case we don't have such an easy visable layer rather a faint increased backscatter coefficient, which might have originated from a distinct layer but due to several different processes this layer lost its borders.
- Line 404: Aitken? => thank you, corrected
- Line 472: I am afraid that I cannot see this in Figure 15. There are quite many gray curves. => This figure shall give an overview of a many different pathways from the Arctic to the position, where the air parcel first touches the ground, which is then marked with a coloured circle. We want to emphasize the accumulation of contact points with the boundary layer and the propagation time. The propagation paths are just an additional information about generally the back-trajectories
Citation: https://doi.org/10.5194/egusphere-2024-124-AC1
-
AC1: 'Reply on RC2', Sandra Graßl, 16 Apr 2024
Peer review completion
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Christoph Ritter
Ines Tritscher
Bärbel Vogel
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(4855 KB) - Metadata XML