Potential modulation of Indian Ocean basin mode on the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone

Wang, Jing; Liu, Yanju; Cheng, Fei; Song, Chengyu; Li, Qiaoping; Ding, Yihui; Xu, Xiangde

doi:https://doi.org/10.5194/egusphere-2023-1529

Preprints

https://doi.org/10.5194/egusphere-2023-1529

Preprints

19 Sep 2023

| 19 Sep 2023

Potential modulation of Indian Ocean basin mode on the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone

Jing Wang, Yanju Liu, Fei Cheng, Chengyu Song, Qiaoping Li, Yihui Ding, and Xiangde Xu

Abstract. Based on long-term observational and reanalysis datasets from 1901 through 2014, this study investigates the characteristics and physical causes of the interdecadal variations in the summer precipitation over the East Asian monsoon boundary zone (EAMBZ). Observational evidence reveals that the EAMBZ precipitation featured prominent interdecadal fluctuations, e.g., with dry summers during the periods preceding 1927, 1968–1982, and 1998–2010, and wet summers during the periods of 1928–1938, 1946–1967, and 2011 onwards. Further analyses identify that the Indian Ocean basin mode (IOBM) is an important oceanic modulator responsible for the interdecadal variations of the EAMBZ precipitation. When the cold phase of the IOBM occurs, an anomalous cyclonic circulation is excited around the northeast corner of the tropical Indian Ocean, which further induces a “north-low–south-high” meridional seesaw pattern over the Northeast China–subtropical western Pacific (SWP) sector. Such seesaw pattern is conducive to the enhanced EAMBZ precipitation through linking favorable environments for the transportation of water vapor from the SWP and the convergence over EAMBZ at interdecadal timescales. For this reason, a physical-empirical model for the EAMBZ precipitation is developed in terms of the IOBM cooling, which can well capture its interdecadal fluctuations and reflect their steady relationship. The key physical pathway connecting the IOBM cooling with the interdecadal variations of the summer EAMBZ precipitation is supported by the numerical results based on the large ensemble experiment and the Indian Ocean pacemaker experiment. Our findings may provide new insights into the understanding of the causes of the interdecadal variations in the summer EAMBZ precipitation, which may favor the long-term policy decision making for the local hydrometeorological planning.

Received: 06 Jul 2023 – Discussion started: 19 Sep 2023

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Journal article(s) based on this preprint

30 Apr 2024

Role of the Indian Ocean basin mode in driving the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone

Jing Wang, Yanju Liu, Fei Cheng, Chengyu Song, Qiaoping Li, Yihui Ding, and Xiangde Xu

Atmos. Chem. Phys., 24, 5099–5115, https://doi.org/10.5194/acp-24-5099-2024,https://doi.org/10.5194/acp-24-5099-2024, 2024

Short summary

Jing Wang, Yanju Liu, Fei Cheng, Chengyu Song, Qiaoping Li, Yihui Ding, and Xiangde Xu

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-1529', Anonymous Referee #1, 17 Oct 2023

This paper uses observations, re-analysis output and model simulations to examine interdecadal variability in the East Asian monsoon boundary zone, particularly in precipitation. The authors find that the cold phase of the Indian Ocean basin mode prompts anomalous cyclonic circulation over the north-eastern Indian Ocean, which ultimately enhances moisture transport from the Pacific Ocean to the boundary zone. I apologise to the authors for the delay in submitting this review.
I have a few a few comments about this paper, primarily about the presentation and discussion. I recommend major revisions.
This paper uses far too many acronyms: I counted 30 in total. While some are fine to keep – if they are mentioned more than five or so times – others are used sparingly. Unfortunately, this makes large sections of the paper very difficult to follow: I spent a great deal of time trying to remember what each acronym was, or flicking backwards to look it up again. Consequently, I found the science message was often unclear. (And as something of an aside, a couple of acronyms were poorly chosen: EU commonly means European Union, and P-E could be confused with “precipitation minus evaporation”, particularly to an audience of atmospheric scientists.)
The coastlines plotted on the figures are very faint: it is difficult to pick out the important features when it’s unclear where they are. Also, axes and colour bars should be labelled on the figures as well as in the captions. And in Figure 6, hatching is used to indicate significance, whereas in other figures the authors use dots: please use just one for consistency.
I think the authors need to include more details about the model simulations described in Section 2.6 They subtract one set of simulations from the other, but it is not clear to me how this achieves the authors’ stated goal (line 205). Please. Explain make clear how the two sets of simulations are different: why is internal variability arising from Indian Ocean SSTs unique to one simulation and not the other? And indeed – and I apologise if I have missed something – it is unclear how these models are used subsequently. I think it would be helpful to note, as the results are discussed, which data sets are being used at each point.
The physical-based empirical model (Section 3.4) appears to be behind a key result of the paper: it is mentioned in the abstract. But this section feels rather brief. Could the authors perhaps discuss the implications of their model a bit further? They say it captures some of the observed interdecadal variability: what about its shortcomings? How is this result helpful?
And related to the above point, I think the discussion (Section 4) could be improved. At present, it summarises the results – which are they summarised again in the Conclusion – but gives little sense of how the results fit into existing knowledge. How does this work move the field forward? What questions arise from it?

Citation: https://doi.org/10.5194/egusphere-2023-1529-RC1
- AC1: 'Reply on RC1', Jing Wang, 12 Dec 2023
  
  Response to Reviewer # 1
  
  Citation: https://doi.org/10.5194/egusphere-2023-1529-AC1
RC2:
'Comment on egusphere-2023-1529', Anonymous Referee #2, 13 Nov 2023
Review of “Potential modulation of Indian Ocean basin mode on the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone” by Jing Wang et al.

This study looks into the link between the Indian Ocean Basin mode (IOBM) and the summer precipitation over the East Asian monsoon boundary zone (EAMBZ). The authors discusses, during cold phase of IOBM, the EAMBZ has enhanced precipitation. This is through the formation of an anomalous cycolonic circulation in the North-East corner of tropical Indian Ocean driving a North-low-South-high pattern taking place in the interdecadal timescales.
Overall, this study attempts to understand the features of precipitation over EAMBZ on interdecadal timescales. I would recommend this study for major revision and has to address below queries:
Major comments:
The title is not clear. It seems to not highlight that this study investigates how modulation of IOBM causes a a change in precipitation in the EAMBZ on interdecadal timescales. The title could be changed to “Modulation of Indian Ocean basin mode potentially drives the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone”. The authors ought to think on this and clarify.

The study primarily provides mechanistic explanation on the link between IOBM and precipitation over EAMBZ during the cold phase only. The authors need to provide and discuss the processes during the IOBM warm phase and corresponding precipitation over EAMBZ, or is it that the authors discuss this somewhere and I have missed it.

I would urge the authors to make clear discussion on past studies (it is there already but somehow the present structure mingles them) which investigates the interannual variations of precipitation over EAMBZ. I recommend the literature review made in the “Introduction" to be more structured. Right now it reads unclear and less motivating to read through. Section 2 in the manuscript for instance, is very well structured and written. Another concern, far too many acronyms are used.

IN addition, as the authors have discussed several processes that are interlinked and connects the IOBM and EAMBZ precipitation. It is necessary that they provide a schematic and/or flowchart showing the interlinkages and processes. This is would be very helpful for the readers .

Minor Comments:
Figure 1- Improve the resolution. It is a key figure.
P2L82-83: I would urge the authors to be elaborate here.
P6L241: I also find dry summers around 1940. Authors mention about Si et al. 2021 here. Please write the context, since that paper looks into Northeast Asian summer monsoon and AMO.
P8L320: “localised atmospheric responses” Please explain.
Equation5: The P-E model, please discuss the possible inabilities of this model. Also, is this model developed for this study (as mentioned in abstract) or does it follows from past studies such as Jeong et al. 2021. Please make this clear.
Citation: https://doi.org/10.5194/egusphere-2023-1529-RC2
- AC2: 'Reply on RC2', Jing Wang, 12 Dec 2023
  
  Response to Reviewer # 2
  
  Citation: https://doi.org/10.5194/egusphere-2023-1529-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-1529', Anonymous Referee #1, 17 Oct 2023

This paper uses observations, re-analysis output and model simulations to examine interdecadal variability in the East Asian monsoon boundary zone, particularly in precipitation. The authors find that the cold phase of the Indian Ocean basin mode prompts anomalous cyclonic circulation over the north-eastern Indian Ocean, which ultimately enhances moisture transport from the Pacific Ocean to the boundary zone. I apologise to the authors for the delay in submitting this review.
I have a few a few comments about this paper, primarily about the presentation and discussion. I recommend major revisions.
This paper uses far too many acronyms: I counted 30 in total. While some are fine to keep – if they are mentioned more than five or so times – others are used sparingly. Unfortunately, this makes large sections of the paper very difficult to follow: I spent a great deal of time trying to remember what each acronym was, or flicking backwards to look it up again. Consequently, I found the science message was often unclear. (And as something of an aside, a couple of acronyms were poorly chosen: EU commonly means European Union, and P-E could be confused with “precipitation minus evaporation”, particularly to an audience of atmospheric scientists.)
The coastlines plotted on the figures are very faint: it is difficult to pick out the important features when it’s unclear where they are. Also, axes and colour bars should be labelled on the figures as well as in the captions. And in Figure 6, hatching is used to indicate significance, whereas in other figures the authors use dots: please use just one for consistency.
I think the authors need to include more details about the model simulations described in Section 2.6 They subtract one set of simulations from the other, but it is not clear to me how this achieves the authors’ stated goal (line 205). Please. Explain make clear how the two sets of simulations are different: why is internal variability arising from Indian Ocean SSTs unique to one simulation and not the other? And indeed – and I apologise if I have missed something – it is unclear how these models are used subsequently. I think it would be helpful to note, as the results are discussed, which data sets are being used at each point.
The physical-based empirical model (Section 3.4) appears to be behind a key result of the paper: it is mentioned in the abstract. But this section feels rather brief. Could the authors perhaps discuss the implications of their model a bit further? They say it captures some of the observed interdecadal variability: what about its shortcomings? How is this result helpful?
And related to the above point, I think the discussion (Section 4) could be improved. At present, it summarises the results – which are they summarised again in the Conclusion – but gives little sense of how the results fit into existing knowledge. How does this work move the field forward? What questions arise from it?

Citation: https://doi.org/10.5194/egusphere-2023-1529-RC1
- AC1: 'Reply on RC1', Jing Wang, 12 Dec 2023
  
  Response to Reviewer # 1
  
  Citation: https://doi.org/10.5194/egusphere-2023-1529-AC1
RC2:
'Comment on egusphere-2023-1529', Anonymous Referee #2, 13 Nov 2023
Review of “Potential modulation of Indian Ocean basin mode on the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone” by Jing Wang et al.

This study looks into the link between the Indian Ocean Basin mode (IOBM) and the summer precipitation over the East Asian monsoon boundary zone (EAMBZ). The authors discusses, during cold phase of IOBM, the EAMBZ has enhanced precipitation. This is through the formation of an anomalous cycolonic circulation in the North-East corner of tropical Indian Ocean driving a North-low-South-high pattern taking place in the interdecadal timescales.
Overall, this study attempts to understand the features of precipitation over EAMBZ on interdecadal timescales. I would recommend this study for major revision and has to address below queries:
Major comments:
The title is not clear. It seems to not highlight that this study investigates how modulation of IOBM causes a a change in precipitation in the EAMBZ on interdecadal timescales. The title could be changed to “Modulation of Indian Ocean basin mode potentially drives the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone”. The authors ought to think on this and clarify.

The study primarily provides mechanistic explanation on the link between IOBM and precipitation over EAMBZ during the cold phase only. The authors need to provide and discuss the processes during the IOBM warm phase and corresponding precipitation over EAMBZ, or is it that the authors discuss this somewhere and I have missed it.

I would urge the authors to make clear discussion on past studies (it is there already but somehow the present structure mingles them) which investigates the interannual variations of precipitation over EAMBZ. I recommend the literature review made in the “Introduction" to be more structured. Right now it reads unclear and less motivating to read through. Section 2 in the manuscript for instance, is very well structured and written. Another concern, far too many acronyms are used.

IN addition, as the authors have discussed several processes that are interlinked and connects the IOBM and EAMBZ precipitation. It is necessary that they provide a schematic and/or flowchart showing the interlinkages and processes. This is would be very helpful for the readers .

Minor Comments:
Figure 1- Improve the resolution. It is a key figure.
P2L82-83: I would urge the authors to be elaborate here.
P6L241: I also find dry summers around 1940. Authors mention about Si et al. 2021 here. Please write the context, since that paper looks into Northeast Asian summer monsoon and AMO.
P8L320: “localised atmospheric responses” Please explain.
Equation5: The P-E model, please discuss the possible inabilities of this model. Also, is this model developed for this study (as mentioned in abstract) or does it follows from past studies such as Jeong et al. 2021. Please make this clear.
Citation: https://doi.org/10.5194/egusphere-2023-1529-RC2
- AC2: 'Reply on RC2', Jing Wang, 12 Dec 2023
  
  Response to Reviewer # 2
  
  Citation: https://doi.org/10.5194/egusphere-2023-1529-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Jing Wang on behalf of the Authors (12 Dec 2023) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (12 Dec 2023) by Peer Nowack

RR by Anonymous Referee #2 (15 Jan 2024)

Suggestions for revision or reasons for rejection

The revised manuscript has improved and the authors have addressed the comments. I thank the authors to include the schematic Figure 12 in the revised manuscript. However, yet at this revision as well I believe that the authors have not clearly stated what is new in this study and different from past studies. Ambiguity exists. I recommend for major revision, I have listed my comments below and request the authors to address them.

Major comments:
P3L100-103: The authors seek to address two questions 1) if there is interdecadal variations in the JJA EAMBZ precipitation? 2) if this is there then how IOBM and EAMBZ precipitation are interlinked? There are past studies such as Si et al. 2021(in their Figure 2) which showed the interdecadal fluctuations based on CRU-TS3.26 from 1900-2012 and also some station data from near Yangtze River which typically answers the first question this study is asking. This study uses the same CRU dataset but from 1901- 2014. Similarly, for the second question, past studies such as Zhang et al. 2018 did discuss and study the connection between IOBM and EAMBZ precipitation.

Although this study cite both Si et al. 2021 and Zhang et al. 2018, but the authors did not clarify what is new in this study compared to the past ones.

Zhang, Z., Sun, X. and Yang, X.-Q., 2018: Understanding the interdecadal variability of East Asian summer monsoon Understanding the Interdecadal Variability of East Asian Summer Monsoon Precipitation: Joint Influence of Three Oceanic Signals DOI: 10.1175/JCLI-D-17-0657.1

Si, D., Jiang, D., Hu, A. and Lang, X., 2021:Variations in northeast Asian summer precipitation driven by the Atlantic multidecadal oscillation DOI: 10.1002/joc.6912

Abstract-L18-20: from observations, the interdecadal variations in the summer precipitation over EAMBZ has been shown by past studies and not a new finding. The authors could cite past studies or may include “as previously shown”…

Abstract-L20-22:The IOBM connection to EAMBZ has been discussed by past studies such as Zhang et al. 2018, also cited by the authors. Here, it is important to clearly separate out the past findings and mention clearly the findings of this new study.

Abstract-L26-28:The physical-empirical model has its own limitations, so again clarifying that as included by the authors in this revised manuscript.

Minor Comments:
P2L61-182: Is this discussion on the interannual variability in the summer EAMBZ precipitation really needed? The authors may want remove this paragraph.

P3L90: Please replace “as well as” to “while”

The authors write “oceanic interdecadal signals” in P3L92-93 and in the next sentence P3L95, they say referring to same as “interdecadal oceanic forcing”. Generally, “signal” refers to response to some forcing. Please clarify.

Similarly, in P6L214: Please rephrase “external radiative forcing signals”. I believe the authors mean “the radiative forcing due to external perturbations such as GHGs”

P6L215-219: This is not clear. Taking an ensemble mean removes the internal variability and gives an estimate of forced response. So taking the ensemble mean from both CESM1_LENS and CESM1_IOPES would remove the variability. Please clarify.

P8L307-308: At this point please explain here how this study is different from the past studies looking at the connection between IOBM and EAMBZ precipitation.

Hide

RR by Anonymous Referee #1 (15 Jan 2024)

ED: Reconsider after major revisions (18 Jan 2024) by Peer Nowack

AR by Jing Wang on behalf of the Authors (11 Feb 2024) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (29 Feb 2024) by Peer Nowack

RR by Anonymous Referee #2 (19 Mar 2024)

ED: Publish subject to minor revisions (review by editor) (19 Mar 2024) by Peer Nowack

AR by Jing Wang on behalf of the Authors (20 Mar 2024) Author's response Author's tracked changes Manuscript

ED: Publish as is (20 Mar 2024) by Peer Nowack

AR by Jing Wang on behalf of the Authors (22 Mar 2024)

Journal article(s) based on this preprint

30 Apr 2024

Role of the Indian Ocean basin mode in driving the interdecadal variations of summer precipitation over the East Asian monsoon boundary zone

Jing Wang, Yanju Liu, Fei Cheng, Chengyu Song, Qiaoping Li, Yihui Ding, and Xiangde Xu

Atmos. Chem. Phys., 24, 5099–5115, https://doi.org/10.5194/acp-24-5099-2024,https://doi.org/10.5194/acp-24-5099-2024, 2024

Short summary

Jing Wang, Yanju Liu, Fei Cheng, Chengyu Song, Qiaoping Li, Yihui Ding, and Xiangde Xu

Supplement

https://doi.org/10.5194/egusphere-2023-1529-supplement

Jing Wang, Yanju Liu, Fei Cheng, Chengyu Song, Qiaoping Li, Yihui Ding, and Xiangde Xu

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Based on long-term observational, reanalysis, and numerical model simulation datasets from 1901 through 2014, this study identify that precipitation over the East Asian monsoon boundary zone featured prominent interdecadal changes, with dry summers during the periods preceding 1927, 1968–1982, and 1998–2010, and wet summers during the periods of 1928–1938, 1946–1967, and 2011 onwards. The Indian Ocean basin mode is an important oceanic modulator responsible for its interdecadal variations.


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