the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Jan 2024
Impact of Asian aerosols on the summer monsoon strongly modulated by regional precipitation biases
Abstract. Reliable attribution of Asian summer monsoon variations to aerosol forcing is critical to reducing uncertainties in future projections of regional water availability, which is of utmost importance for risk management and adaptation planning in this densely populated region. Yet, simulating the monsoon remains a challenge for climate models which suffer from long-standing biases, undermining their reliability in attributing anthropogenically-forced changes. We analyse a suite of climate model experiments to identify a link between model biases and monsoon responses to Asian aerosols, and the physical mechanism underpinning this link, including the role of large-scale circulation changes. The aerosol impact on monsoon precipitation and circulation is strongly influenced by a model’s ability to simulate the spatial distribution and temporal variability of the climatological monsoon winds, clouds and precipitation across Asia, which critically modulates the magnitude and efficacy of aerosol-cloud-precipitation interactions, the predominant driver of the total aerosol response. There is a strong interplay between South and East Asia monsoon precipitation biases and their relative predominance in driving the overall monsoon response. We found a striking contrast between the early and late summer aerosol-driven changes ascribable to opposite signs and seasonal evolution of the biases in the two regions. A realistic simulation of the evolution of the large-scale atmospheric circulation is crucial to realise the full extent of the aerosol impact over Asia. These findings provide important implications to better understand and constrain the diversity and inconsistencies of model responses to aerosol changes over Asia in historical simulations and future projections.
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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
(8417 KB) - Metadata XML
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Supplement
(10659 KB) - BibTeX
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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-2023-3136', Anonymous Referee #1, 02 Feb 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-3136/egusphere-2023-3136-RC1-supplement.pdf
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AC1: 'Reply on RC1', Zhen Liu, 18 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-3136/egusphere-2023-3136-AC1-supplement.pdf
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AC1: 'Reply on RC1', Zhen Liu, 18 Apr 2024
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RC2: 'Comment on egusphere-2023-3136', Anonymous Referee #2, 02 Feb 2024
This study examines the link between monsoon biases relative to observations and monsoon response to anthropogenic aerosols in Asia in terms of monsoonal precipitation, circulations, moisture budget using numerical experiments. The paper tries to address an important question: how do modelled precipitation biases influence anthropogenic aerosol-induced monsoon changes. Overall, it is an interesting paper with detailed analysis. At the same time, it is a very long paper: 8 figures in the main text plus 15 figures in the supplementary materials. The authors should include as many figures as possible in the main text rather than in the supplementary. The figures are not clearly labelled (some figure captions are misleading); some figures in the supplementary materials can be combined with the figures in the main text. I suggest the authors include all simulations/experiments in Table 1 with clear description. The result part contains too much discussion of previous studies, which significantly distract the audience’s attention. The discussion can be replaced to a new Discussion section close to the end of the paper. Moreover, the sections in the Result 3.1 and 3.2 now are too long and may be divided into subsections. Overall, it is hard to follow the entire paper (I have to often refer to the supplementary figures). I hope by reorganizing the result sections, redesigning some of the figures, correcting figure captions, the authors could improve the quality of the manuscript in a significant way to meet the standards of ACP.
Major comments
In several places, the authors mentioned that aerosol–cloud interactions dominate the aerosol-induced monsoonal changes, for example, Line 512. In my understanding, aerosol–radiation interactions also play an important role in modulating monsoon rainfall, sometime even a bigger role than aerosol–cloud interactions. I saw the authors analyzed the cloud responses to anthropogenic aerosols. However, without a direct comparison of monsoonal precipitation responses to aerosol–cloud interactions and aerosol–radiation interactions, the authors should be careful with their wording. I am wondering if the authors could separate the two interactions in their analysis/model, which would provide very interesting analysis and results and improve the scientific implication of this paper.
- Line 47: It is not clear what trends are driven by aerosols?
- Line 98: What is the GLOMAP scheme? Spell out its full name.
- 1b: Caption is not clear: why emissions can be negative, should be emission differences.
- Line 181–182: Northern India should be deleted because precipitation increases is not statistically significant.
- 2b–2c: grid cells with statistically significant changes represented by shadings should be highlighted as in Fig. 2a.
- Lines 183–184: “The simultaneous northwestward shift and strengthening of the Mascarene High over the equatorial Indian” is not shown in Fig. 2. The white colors represent close-to-zero changes in SLP.
- What’s the difference between Fig. 1 and Fig. S9?
- S1 can be combined with Fig. 2 with 3 rows and 2 columns.
- Line 201: should be “aerosol-driven rainfall difference pattern.”
- 3a: Why not use the same period for model and observations: 2003–2012? Monsoon precipitation shows strong interannual and decadal variations, which should be considered when comparing model and observations.
- Titles of Figs 3b–3h are misleading, they should be responses not the variables themselves
- Line 505: delete “also”
- Line 512: “The aerosol influence on the monsoon, driven by the magnitude of aerosol–cloud interactions”: How about aerosol–radiation interactions?
Citation: https://doi.org/10.5194/egusphere-2023-3136-RC2 -
AC2: 'Reply on RC2', Zhen Liu, 18 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-3136/egusphere-2023-3136-AC2-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-3136', Anonymous Referee #1, 02 Feb 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-3136/egusphere-2023-3136-RC1-supplement.pdf
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AC1: 'Reply on RC1', Zhen Liu, 18 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-3136/egusphere-2023-3136-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Zhen Liu, 18 Apr 2024
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RC2: 'Comment on egusphere-2023-3136', Anonymous Referee #2, 02 Feb 2024
This study examines the link between monsoon biases relative to observations and monsoon response to anthropogenic aerosols in Asia in terms of monsoonal precipitation, circulations, moisture budget using numerical experiments. The paper tries to address an important question: how do modelled precipitation biases influence anthropogenic aerosol-induced monsoon changes. Overall, it is an interesting paper with detailed analysis. At the same time, it is a very long paper: 8 figures in the main text plus 15 figures in the supplementary materials. The authors should include as many figures as possible in the main text rather than in the supplementary. The figures are not clearly labelled (some figure captions are misleading); some figures in the supplementary materials can be combined with the figures in the main text. I suggest the authors include all simulations/experiments in Table 1 with clear description. The result part contains too much discussion of previous studies, which significantly distract the audience’s attention. The discussion can be replaced to a new Discussion section close to the end of the paper. Moreover, the sections in the Result 3.1 and 3.2 now are too long and may be divided into subsections. Overall, it is hard to follow the entire paper (I have to often refer to the supplementary figures). I hope by reorganizing the result sections, redesigning some of the figures, correcting figure captions, the authors could improve the quality of the manuscript in a significant way to meet the standards of ACP.
Major comments
In several places, the authors mentioned that aerosol–cloud interactions dominate the aerosol-induced monsoonal changes, for example, Line 512. In my understanding, aerosol–radiation interactions also play an important role in modulating monsoon rainfall, sometime even a bigger role than aerosol–cloud interactions. I saw the authors analyzed the cloud responses to anthropogenic aerosols. However, without a direct comparison of monsoonal precipitation responses to aerosol–cloud interactions and aerosol–radiation interactions, the authors should be careful with their wording. I am wondering if the authors could separate the two interactions in their analysis/model, which would provide very interesting analysis and results and improve the scientific implication of this paper.
- Line 47: It is not clear what trends are driven by aerosols?
- Line 98: What is the GLOMAP scheme? Spell out its full name.
- 1b: Caption is not clear: why emissions can be negative, should be emission differences.
- Line 181–182: Northern India should be deleted because precipitation increases is not statistically significant.
- 2b–2c: grid cells with statistically significant changes represented by shadings should be highlighted as in Fig. 2a.
- Lines 183–184: “The simultaneous northwestward shift and strengthening of the Mascarene High over the equatorial Indian” is not shown in Fig. 2. The white colors represent close-to-zero changes in SLP.
- What’s the difference between Fig. 1 and Fig. S9?
- S1 can be combined with Fig. 2 with 3 rows and 2 columns.
- Line 201: should be “aerosol-driven rainfall difference pattern.”
- 3a: Why not use the same period for model and observations: 2003–2012? Monsoon precipitation shows strong interannual and decadal variations, which should be considered when comparing model and observations.
- Titles of Figs 3b–3h are misleading, they should be responses not the variables themselves
- Line 505: delete “also”
- Line 512: “The aerosol influence on the monsoon, driven by the magnitude of aerosol–cloud interactions”: How about aerosol–radiation interactions?
Citation: https://doi.org/10.5194/egusphere-2023-3136-RC2 -
AC2: 'Reply on RC2', Zhen Liu, 18 Apr 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-3136/egusphere-2023-3136-AC2-supplement.pdf
Peer review completion
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Massimo Bollasina
Laura Wilcox
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(8417 KB) - Metadata XML
-
Supplement
(10659 KB) - BibTeX
- EndNote
- Final revised paper