the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Dec 2022
Multidecadal variability of the ITCZ from the Last Millennium Extreme Precipitation Changes in Northeastern Brazil
Abstract. Decadal and multidecadal variability of the Intertropical Convergence Zone (ITCZ) is analyzed in space-time using CMIP6 simulations and paleoprecipitation records during the Last Millennium. We investigated the persistence patterns of the CMIP6 ensemble models, using low frequency component analysis (LFCA) to isolate the mechanisms that modulate the ITCZ at the multidecadal scale. The results suggest that the north-south displacement of the ITCZ was related to the oceanic region with the highest sea surface temperature (SST) of the tropical South Atlantic basin. The zonal mode variability is initially associated with the equatorial region (between 5° S and 5° N) and with the northwestern African coast. These observations also contrast with the paleoclimatic records of the region, indicating a northward shift of the ITCZ during the MCA and a southward shift during the LIA. Based on the periodicities observed the 21 years is predominant during the Last Millennium can be associated with the solar cycle influence on the pattern of ITCZ contracted and positioned in the central region of the equator. This relationship suggests that, although ENSO is the main driver in variability over Tropical South America at interannual time scales, this influence can be significantly modulated by longer time scales. The results suggest the existence of a low-frequency variability, modifying the distribution of precipitation and with consequences in the intensity and frequency of droughts/floods events in the NE, indicating that these events are associated with the coupling between the oceans and the atmosphere.
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Status: closed
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RC1: 'Comment on egusphere-2022-785', Anonymous Referee #1, 27 Feb 2023
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AC1: 'Reply on RC1', I. Vásquez, 22 May 2023
Thank you for your comments. We apologize for any difficulties and confusion it may have caused. We appreciate your suggestions. The manuscript has been revised, paying special attention to the clarity of the structure, the main objective of the paper, and the description of the methods. We will also ensure that the English language is reviewed and corrected. Thank you again for your valuable input.
We attach the document with the responses to each of your indications. Thank you
-
AC1: 'Reply on RC1', I. Vásquez, 22 May 2023
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RC2: 'Comment on egusphere-2022-785', Anonymous Referee #2, 27 Feb 2023
Review of “Multidecadal variability of the ITCZ from the Last Millennium Extreme Precipitation Changes in Northeastern Brazil” by Isela L. Vásquez P et al.
Authors have investigated low frequency components of decadal-multidecadal ITCZ variability in the Last Millennium experiment and compared results with some proxy. They found a meridional mode coherent with ITCZ migration and a zonal mode associated with east-west shift of precipitation in the Atlantic. Authors have linked the 21-year periodicity to solar cycle superimposed to longer periodicity. The manuscript is so poorly written that is almost impossible to go through results. The rational structure is not clear as well as the main goal of the paper. Methods are also poorly described and the overall text seems a collection of this and that without focus. I encourage the authors to carefully revise the text putting particular emphasis on the English.
Abstract
Ln 7: what is MCA? Acronyms not spelled before.
Ln 8: LIA as well… I guess it is Little Ice Age, but for many people in the field not focused on paleoclimate, this needs to be spelled it out.
Ln 8-10: The sentence needs some rephrasing. Please consider the following rephrasing:
“Based on our results, the 21-year periodicity associated with solar cycle is predominant during the Last Millennium. It influences the tropical rainfall pattern and favours a contraction and an equatorward shift of the ITCZ.”
Ln 18: remove [meet and], replace [maxima] with [peak].
Ln 20: dynamic -> dynamics
Ln 20 – 34: please revisit the literature considering the energy framework described in:
Broccoli, A. J., K. A. Dahl, and R. J. Stouffer, 2006: Response of the ITCZ to northern hemisphere cooling. Geophysical Research Letters, 33, L01702, doi:10.1029/2005GL024546.
Marshall, J., A. Donohoe, D. Ferreira, and D. McGee, 2013: The ocean’s role in setting the mean position of the atmosphere’s ITCZ. Climate Dynamics, 42, 1967–1979, doi:10.1007/s00382-013-1767-z.
Donohoe, A., J.Marshall, D. Ferreira, andD.McGee, 2013: The relationship between ITCZ location and cross equatorial atmospheric heat transport; from the seasonal cycle to the Last Glacial Maximum. Journal of Climate, 26, 3597–3618, doi:10.1175/JCLI-D-12-00467.1.
Boos, W. R., & Korty, R. L. (2016). Regional energy budget control of the intertropical convergence zone and application to mid-Holocene rainfall. Nature Geoscience, 9(12), 892-897.
In particular it is valuable for this study to connect shifts in the ITCZ with insolation and Net Energy Input at the equator.
Authors might also want to refer to Southern Hemisphere monsoon precipitation in midHolocene and rcp8.5 where ITCZ and tropical precipitation has been linked to changes in net energy input by D’Agostino et al., 2020
D’Agostino, R., Brown, J. R., Moise, A., Nguyen, H., Dias, P. L. S., & Jungclaus, J. (2020). Contrasting southern hemisphere monsoon response: MidHolocene orbital forcing versus future greenhouse gas–induced global warming. Journal of Climate, 33(22), 9595-9613.
Ln 42: what is Neotropics?
Ln 56: what is NEB? Please check that every acronyms have been spelled before invoking them!
Ln 55 – 70. Please revisit the mechanisms accounting for energy variations instead focusing on Sea Surface Temperature anomalies.
Ln 69: what is the difference between Atlantic Meridional Mode and Atlantic Multidecadal Oscillation or Variability? Can you indicate typical latitudes or periodicities?
Table 1: you can indicate the resolution for each model and CMIP phase and eventually indicate if the model has prescribed/dynamic vegetation.
Subsection 4.1: it might be beneficial for the paper including also a brief discussion about the modelled onset and withdrawn of South American monsoon (specifically for North Eastern Brazilian precipitation) that might be delayed given the bias in DJF – MAM with GPCP of the Atlantic ITCZ to which it is strictly connected. The whole section is poorly written.
Ln 140: “Probabilistic The location of the ITCZ”: there must be a typo somewhere.
Ln 144-145: “Our results indicate that the CMIPs models simulate a migration of the ITCZ towards the south in relation to those observed in the DJF and MAM periods.” To those what? Not clear this sentence to me. And afterwards “Atlantic bias greater relative to …” than what? Are your referring to a spatial or temporal comparison??? Not clear and additionally check the English please.
Ln 180: title of section 4.2: something weird in “The Interdecadal Component temporal of the ITCZ latitudinal location” -> check the English: remove temporal!
Ln 181: Furthermore, replace “this study isolates” with “this section is focused on”.
Ln 181-182 “Our analysis identifies the multidecadal Atlantic SST variability over the subpolar North Atlantic.” This sentence is weird. You can either say “The LFCA analysis allows us to extract and isolate multidecadal periodicities in the subpolar North Atlantic SST overall variability” for example, otherwise it sounds odd. Additionally, perhaps I did not get it but did you apply the method to subpolar North Atlantic only or to Atlantic sector?
Ln 190: what is deltaDwax?
Ln 196: what is %Ti?
Results and discussion section:
I found the entire discussion of Results poorly written. It is very hard to follow. The section contains too many acronyms. Somehow also how the results are structured is confusing. I strongly recommend to rewrite the section being more rational in the way the results are described.
Citation: https://doi.org/10.5194/egusphere-2022-785-RC2 -
AC2: 'Reply on RC2', I. Vásquez, 22 May 2023
Thank you for your comments. We apologize for any difficulties and confusion it may have caused. We appreciate your suggestions. The manuscript has been revised, paying special attention to the clarity of the structure, the main objective of the paper, and the description of the methods. We will also ensure that the English language is reviewed and corrected. Thank you again for your valuable input.
We attach the document with the responses to each of your indications. Thank you
-
AC2: 'Reply on RC2', I. Vásquez, 22 May 2023
-
EC1: 'Comment on egusphere-2022-785', Martin Claussen, 23 May 2023
Dear authors,
Thank you very much for your thorough response to the referees’ comments. The referees have raised serious concern regarding the presentation of your method and results. They would like to see a carefully revised manuscript. Therefore, I invite you to submit a revised manuscript which will be reviewed by the referees.
Best regards,
Martin Claussen
Citation: https://doi.org/10.5194/egusphere-2022-785-EC1 - AC3: 'Reply on EC1', I. Vásquez, 29 May 2023
Status: closed
-
RC1: 'Comment on egusphere-2022-785', Anonymous Referee #1, 27 Feb 2023
-
AC1: 'Reply on RC1', I. Vásquez, 22 May 2023
Thank you for your comments. We apologize for any difficulties and confusion it may have caused. We appreciate your suggestions. The manuscript has been revised, paying special attention to the clarity of the structure, the main objective of the paper, and the description of the methods. We will also ensure that the English language is reviewed and corrected. Thank you again for your valuable input.
We attach the document with the responses to each of your indications. Thank you
-
AC1: 'Reply on RC1', I. Vásquez, 22 May 2023
-
RC2: 'Comment on egusphere-2022-785', Anonymous Referee #2, 27 Feb 2023
Review of “Multidecadal variability of the ITCZ from the Last Millennium Extreme Precipitation Changes in Northeastern Brazil” by Isela L. Vásquez P et al.
Authors have investigated low frequency components of decadal-multidecadal ITCZ variability in the Last Millennium experiment and compared results with some proxy. They found a meridional mode coherent with ITCZ migration and a zonal mode associated with east-west shift of precipitation in the Atlantic. Authors have linked the 21-year periodicity to solar cycle superimposed to longer periodicity. The manuscript is so poorly written that is almost impossible to go through results. The rational structure is not clear as well as the main goal of the paper. Methods are also poorly described and the overall text seems a collection of this and that without focus. I encourage the authors to carefully revise the text putting particular emphasis on the English.
Abstract
Ln 7: what is MCA? Acronyms not spelled before.
Ln 8: LIA as well… I guess it is Little Ice Age, but for many people in the field not focused on paleoclimate, this needs to be spelled it out.
Ln 8-10: The sentence needs some rephrasing. Please consider the following rephrasing:
“Based on our results, the 21-year periodicity associated with solar cycle is predominant during the Last Millennium. It influences the tropical rainfall pattern and favours a contraction and an equatorward shift of the ITCZ.”
Ln 18: remove [meet and], replace [maxima] with [peak].
Ln 20: dynamic -> dynamics
Ln 20 – 34: please revisit the literature considering the energy framework described in:
Broccoli, A. J., K. A. Dahl, and R. J. Stouffer, 2006: Response of the ITCZ to northern hemisphere cooling. Geophysical Research Letters, 33, L01702, doi:10.1029/2005GL024546.
Marshall, J., A. Donohoe, D. Ferreira, and D. McGee, 2013: The ocean’s role in setting the mean position of the atmosphere’s ITCZ. Climate Dynamics, 42, 1967–1979, doi:10.1007/s00382-013-1767-z.
Donohoe, A., J.Marshall, D. Ferreira, andD.McGee, 2013: The relationship between ITCZ location and cross equatorial atmospheric heat transport; from the seasonal cycle to the Last Glacial Maximum. Journal of Climate, 26, 3597–3618, doi:10.1175/JCLI-D-12-00467.1.
Boos, W. R., & Korty, R. L. (2016). Regional energy budget control of the intertropical convergence zone and application to mid-Holocene rainfall. Nature Geoscience, 9(12), 892-897.
In particular it is valuable for this study to connect shifts in the ITCZ with insolation and Net Energy Input at the equator.
Authors might also want to refer to Southern Hemisphere monsoon precipitation in midHolocene and rcp8.5 where ITCZ and tropical precipitation has been linked to changes in net energy input by D’Agostino et al., 2020
D’Agostino, R., Brown, J. R., Moise, A., Nguyen, H., Dias, P. L. S., & Jungclaus, J. (2020). Contrasting southern hemisphere monsoon response: MidHolocene orbital forcing versus future greenhouse gas–induced global warming. Journal of Climate, 33(22), 9595-9613.
Ln 42: what is Neotropics?
Ln 56: what is NEB? Please check that every acronyms have been spelled before invoking them!
Ln 55 – 70. Please revisit the mechanisms accounting for energy variations instead focusing on Sea Surface Temperature anomalies.
Ln 69: what is the difference between Atlantic Meridional Mode and Atlantic Multidecadal Oscillation or Variability? Can you indicate typical latitudes or periodicities?
Table 1: you can indicate the resolution for each model and CMIP phase and eventually indicate if the model has prescribed/dynamic vegetation.
Subsection 4.1: it might be beneficial for the paper including also a brief discussion about the modelled onset and withdrawn of South American monsoon (specifically for North Eastern Brazilian precipitation) that might be delayed given the bias in DJF – MAM with GPCP of the Atlantic ITCZ to which it is strictly connected. The whole section is poorly written.
Ln 140: “Probabilistic The location of the ITCZ”: there must be a typo somewhere.
Ln 144-145: “Our results indicate that the CMIPs models simulate a migration of the ITCZ towards the south in relation to those observed in the DJF and MAM periods.” To those what? Not clear this sentence to me. And afterwards “Atlantic bias greater relative to …” than what? Are your referring to a spatial or temporal comparison??? Not clear and additionally check the English please.
Ln 180: title of section 4.2: something weird in “The Interdecadal Component temporal of the ITCZ latitudinal location” -> check the English: remove temporal!
Ln 181: Furthermore, replace “this study isolates” with “this section is focused on”.
Ln 181-182 “Our analysis identifies the multidecadal Atlantic SST variability over the subpolar North Atlantic.” This sentence is weird. You can either say “The LFCA analysis allows us to extract and isolate multidecadal periodicities in the subpolar North Atlantic SST overall variability” for example, otherwise it sounds odd. Additionally, perhaps I did not get it but did you apply the method to subpolar North Atlantic only or to Atlantic sector?
Ln 190: what is deltaDwax?
Ln 196: what is %Ti?
Results and discussion section:
I found the entire discussion of Results poorly written. It is very hard to follow. The section contains too many acronyms. Somehow also how the results are structured is confusing. I strongly recommend to rewrite the section being more rational in the way the results are described.
Citation: https://doi.org/10.5194/egusphere-2022-785-RC2 -
AC2: 'Reply on RC2', I. Vásquez, 22 May 2023
Thank you for your comments. We apologize for any difficulties and confusion it may have caused. We appreciate your suggestions. The manuscript has been revised, paying special attention to the clarity of the structure, the main objective of the paper, and the description of the methods. We will also ensure that the English language is reviewed and corrected. Thank you again for your valuable input.
We attach the document with the responses to each of your indications. Thank you
-
AC2: 'Reply on RC2', I. Vásquez, 22 May 2023
-
EC1: 'Comment on egusphere-2022-785', Martin Claussen, 23 May 2023
Dear authors,
Thank you very much for your thorough response to the referees’ comments. The referees have raised serious concern regarding the presentation of your method and results. They would like to see a carefully revised manuscript. Therefore, I invite you to submit a revised manuscript which will be reviewed by the referees.
Best regards,
Martin Claussen
Citation: https://doi.org/10.5194/egusphere-2022-785-EC1 - AC3: 'Reply on EC1', I. Vásquez, 29 May 2023
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