the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Drought increased since the mid-20th century in the northern South American Altiplano revealed by a 389-year precipitation record
- 1Laboratorio de Dendrocronología, Universidad Continental, Huancayo, 12000, Peru
- 2Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, CONICET, Mendoza, 5500, Argentina
- 3Laboratorio de Dendrocronología y Cambio Global, Instituto de Conservación Biodiversidad y Territorio, Universidad Austral de Chile, Valdivia, 5110566, Chile
- 4Escuela de Graduados, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile, Valdivia, 5110566, Chile
- 5Center for Climate and Resilience Research (CR)2 , Santiago, 9160000, Chile
- 6Cape Horn International Center (CHIC), Punta Arenas, 6200000, Chile
- 7Lamont-Doherty Earth Observatory of Columbia University, New York, NY10964, United States
- 8CREAF, Bellaterra (Cerdanyola del Vallés), Barcelona, 081093, Spain
- 9ICREA, Pg. Lluís Companys 23, Barcelona, 08010, Spain
- 10Facultad de Ciencias Forestales y del Medio Ambiente, Universidad Nacional del Centro del Perú, Huancayo, Perú, Avenida Mariscal Castilla 3909, Huancayo, 12006, Perú
- 11Missouri Botanical Garden, Pasco, Oxapampa, 19230, Peru
- 1Laboratorio de Dendrocronología, Universidad Continental, Huancayo, 12000, Peru
- 2Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, CONICET, Mendoza, 5500, Argentina
- 3Laboratorio de Dendrocronología y Cambio Global, Instituto de Conservación Biodiversidad y Territorio, Universidad Austral de Chile, Valdivia, 5110566, Chile
- 4Escuela de Graduados, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile, Valdivia, 5110566, Chile
- 5Center for Climate and Resilience Research (CR)2 , Santiago, 9160000, Chile
- 6Cape Horn International Center (CHIC), Punta Arenas, 6200000, Chile
- 7Lamont-Doherty Earth Observatory of Columbia University, New York, NY10964, United States
- 8CREAF, Bellaterra (Cerdanyola del Vallés), Barcelona, 081093, Spain
- 9ICREA, Pg. Lluís Companys 23, Barcelona, 08010, Spain
- 10Facultad de Ciencias Forestales y del Medio Ambiente, Universidad Nacional del Centro del Perú, Huancayo, Perú, Avenida Mariscal Castilla 3909, Huancayo, 12006, Perú
- 11Missouri Botanical Garden, Pasco, Oxapampa, 19230, Peru
Abstract. Given the short span of instrumental precipitation records in the South American Altiplano, long-term hydroclimatic records are needed to understand the nature of climate variability and to improve the predictability of precipitation, a key natural resource for the socio-economic development in the Altiplano and adjacent arid lowlands. In this region grows Polylepis tarapacana, a long-lived tree species that is very sensitive to hydroclimatic changes and have been widely used for tree-ring studies in the central and southern Altiplano. However, in the northern sector of the Peruvian and Chilean Altiplano (16º–19º S) still exist a gap of hydroclimatic tree-ring records. Our study provides an overview of the temporal evolution of annual precipitation for the period 1625–2013 CE at the northern South American Altiplano, allowing for the identification of wet or dry periods based on a regional reconstruction composed by three P. tarapacana chronologies. An increase in the occurrence rate of extreme dry events, together with a decreasing trend in the reconstructed precipitation, have been recorded since the 1970s decade in the northern Altiplano within the context of the last ~four centuries. The average precipitation of the last 17-year stands out as the driest in our 389-years reconstruction. We revealed a temporal and spatial synchrony across the Altiplano region of wet conditions during the first half of the 19th century and the drought conditions since mid 1970s recorded by independent tree-ring based hydroclimate reconstructions and several paleoclimatic records based on other proxies available for the tropical Andes. The rainfall reconstruction provides also valuable information about the ENSO influences in the northern Altiplano precipitation. The spectral properties of the rainfall reconstruction showed strong imprints of ENSO variability at decadal, sub-decadal and inter-annual time-scale, in particular from the Pacific N3 sector. Overall, the remarkable recent reduction in precipitation in comparison with previous centuries, the increase in extreme dry events and the coupling between precipitation and ENSO variability reported by this work is essential information in the context of the growing demand for water resources in the Altiplano that will contribute to a better understanding of the vulnerability/resilience of the region to the projected evapotranspiration increase for the 21st century associated to global warming.
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Mariano S. Morales et al.
Status: closed
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RC1: 'Comment on cp-2022-37', Anonymous Referee #1, 25 May 2022
Dear authors, I read your paper with interest since the topic is super relevant to the dendroclimatology field.
I understand that your main point is to defend the idea of an increased dryness conditions in your study area, based on a tree-ring precipitation reconstruction, however I’m not completely sold on this idea, and you show a brief discussion about it at the end of your discussion in which you mention there are studies (one at least), that show an opposite trend for the same time period, over your study area.
I think one of the key messages would be why would we value the tree-ring based reconstruction of precipitation you are offering over the instrumental data that are currently available. You mention the other paleoclimate proxies, however they have problems like trends that are difficult to remove sometimes.
I raise a few points here, see if you find it interesting to address them.
Abstract:
Lines 35-40: I missed a little explanation of what would be the influences of ENSO in the precipitation in your study area.
In Methods you mention in “Climate data collection and analysis” that you used stations with less than 10% missing data. Why did you make the average of the 7 stations? Did you analyze each station against your chronologies? Or against your regional chronology? Did you try gridded data too?
In line 197, did you try monthly correlations too? I’m confused, did you calculate the average of the entire year?
In line 221, is this your best correlation result? What period is this correlation?
In line 253 you say “stable”, however I think you are comparing this ~ 20 years frequency with the increased frequency you observe in the 20-21th centuries, is that correct? Stable to me sounds like nothing was happening, however it was, but at a lower frequency. I suggest you change the text in this paragraph, there is no such a thing as stable in climate, because it is constantly changing.
In lines 345-347 I ask myself, what are the odds of your chronologies showing decreased growth due to increased temperature and not exactly related to decrease in ppt?
In line 370 you mention 1876/1877, and according to your dated chronology, your 1876 ring is the one that started in November of 1876 and extended to 1877. That would be already when the El Nino happened, and yet you say your 1876 shows as the wettest year.
In line 385 I would suggest you write what BT stands for, I know you already showed in methods, but it’s a long way for the readers to go back and find the abbreviation.
In paragraph 409-416: What is the main source of precipitation in the study area? Is it the Pacific Ocean or the glaciers? Is this drying trend related to losses in ice cover, increased temperature, or both, and are you suggesting increased SST’s activity?
In lines 424-427 you say that these differences in trends could be related to distinct time span, however the instrumental ppt data you are using are also showing negative trend, in opposite to the study published by Segura et al. 2020, is that correct? And in your study, the instrumental data you are also relatively short (~1970-present). Therefore I was asking about why you decided to calculate the average of the 7 stations, even when they had missing data.
Overall, I think this is a great manuscript, the analysis and methodology were well performed. I raised a few questions to you here that I hope can help this narrative. I do think it would be ideal to include more explanation regarding the hydroclimatology in the area, like where does the water come from and the possible explanations for this drying trend.
Below are a few typos I noticed.
Small changes/typos
Introduction:
Line 68: “found”
Line 73: I think you mean to say “by the end of the 2st century”
Line 78-79: I would suggest you only say “changes” instead of “possible current changes”
Line 102: “…the minimum temperature is…”
In “2.7 ENSO signals in the northern Altiplano precipitation” there is a typo when you write NDJ. Right now is written as “NJD”
Discussion
Line 331: “allows”
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AC1: 'Reply on RC1', Mariano Morales, 05 Sep 2022
Dear editor Keely Mills,
Please, find attached our responses to the reviewer 1 comments on our submission to Climate of the Past, entitled “Drought increased since the mid-20th century in the northern South American Altiplano revealed by a 389-year precipitation record”.
We have prepared a new version of the manuscript that addresses most of the comments from the reviewer. In preparing this new version, we have included the two figures that were in the SI to the main text. Figure S1 is now part of Figure 2, while Figure S2 is now Figure 8.
We thank the reviewer for their thoughtful critiques and his time and consideration.
Kind Regards,
Mariano Morales (corresponding author)
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AC1: 'Reply on RC1', Mariano Morales, 05 Sep 2022
-
RC2: 'Comment on cp-2022-37', Anonymous Referee #2, 06 Dec 2022
The paper by Morales et al presents a tree-ring precipitation reconstruction from the northern South American Altiplano that spans the last c. 400 years. The study fills a knowledge gap in the region, whilst simultaneously complementing existing work that has been undertaken a broader scale. I am not a technical expert, so cannot comment on the statistical methodology employed for this paper. In terms of the scientific quality and the "story" from start to finish, this is a very neat and comprehensive piece of research which will be valuable to a range of researchers working on hydroclimate variability in South America. The unique record will add value to disciplines beyond dendrochronology and climate reconstructions - it will be of use to the broader palaeo community and also the archaeological community. The authors often cite the issue of water stress and how this can inform management - and this is alluded to in the text at several points. It could be useful for the authors to articulate exactly how their study can be used in management. It would provide context, but as written can not inform management of water supplies. Perhaps more articulation (in a few sentences) could be included in the discussion section of this paper. Overall the quality of the science and the manuscript is very high. There are a few areas where sentences are a little long, and need to be shortened and/or rephrased to make sure the information is not lost. I attach an annotated manuscript with corrections / edits for the authors to undertake.
-
AC2: 'Reply on RC2', Mariano Morales, 29 Dec 2022
We thank the reviewer for their thoughtful critiques and his time and consideration.
General comments
“The authors often cite the issue of water stress and how this can inform management - and this is alluded to in the text at several points. It could be useful for the authors to articulate exactly how their study can be used in management. It would provide context, but as written can not inform management of water supplies. Perhaps more articulation (in a few sentences) could be included in the discussion section of this paper. Overall the quality of the science and the manuscript is very high. There are a few areas where sentences are a little long, and need to be shortened and/or rephrased to make sure the information is not lost. I attach an annotated manuscript with corrections / edits for the authors to undertake.”
To be more specific about the importance of paleoclimatic records as a source of information potentially useful for decision-makers, we rephrase the following paragraph in the Discussion section:
Droughts are of particular relevance in climate variability for this semi-arid region of the Andes. Therefore, the information provided by this study allows us to understand that mean dry condition dominates the instrumental period and the frequency of occurrence of extreme drought events in the present has no precedent in the past. Under a global warming context, the Altiplano's water resources are fundamental for biodiversity conservation and socioeconomic activities. The projected increase in evapotranspiration as a result of global warming, together with a wide range of variability among the precipitation models projected for the 21st century, may lead to growing demand for water in a region already under water stress. Knowing the long-term hydroclimatic variability in this region, we need to consider whether the current configuration of social and organizational structures are sufficient to provide the resilience and adaptation to successfully address current and future hydroclimatic changes. A better understanding of the future of Altiplano's water resources should be listed as priority for stakeholders and decision-makers to avoid social conflicts at both the local and regional levels. Under this complex political, social and environmental scenario, the results from our study are relevant to plan and implement adaptive strategies to reduce these vulnerabilities in the face of future water shortages.
Specific comments
Line 24. “There are several very long sentences in this abstract. I have tried to split some where possible. Please check that sentences are a little bit shorter - it makes it easier to read.”
The abstract and manuscript were revised in order to shorten, where possible, very long sentences.
Line 29. “CLARIFY - this would need rephrasing - it doesn't quite make sense. What gap? Temporal? Spatial? In our knowledge of hydroclimatic change?”
To be clearer, we rephrase the following sentence:
However, in the northern sector of the Peruvian and Chilean Altiplano (16º-19º S) still exist a gap of hydroclimatic tree-ring records.
By
However, in the northern sector of the Peruvian and Chilean Altiplano (16º-19º S) still exist a gap in our knowledge of high-resolution hydroclimatic change based on tree-ring records.
Line 99 – 102. Do you mean >85% of the rainfall occurs from December to March? If so, you need to clarify this. If not, then it will need to be clarified as I'm not sure I understand. “Can you give actual numbers here - this isn't the best phrasing and has also appeared immediately before”
Thanks for the comment. We rephrase and split the sentence to be shorter and clearer.
The climate is semi-arid with dry-cold winters and rainy-warm summers, with a total annual precipitation that ranges between 290-400 mm. More than 85% of the total annual precipitation occurs during summer (December to March).
Line 300-302. “This description doesn't make sense. Can you rephrase”
To be clearer, we rephrase the following sentence:
Strong correlations (r > -0.42) were recorded centered in the periods 1885-1900, 1940-1955, 1965-1975, while sharp decreases in correlations were found centered in the periods 1910-1935, 1978-2000 (Fig. 6c).
by
Strong negative correlations were recorded centered in the periods 1885-1900, 1940-1955, 1965-1975, while a lost in the relationships was found centered in the periods 1910-1935, 1978-2000 (Fig. 6c).
Line 303-307. “Not sure this makes sense. What explains the high percentage. Need to split sentence into 2 and clarify.”
The following sentence was rephrased:
Both, reconstructed precipitation and SSTs_N3 recorded dominant oscillations modes at decadal (Fig. 6d) and inter-annual (Fig. 6e,f) frequencies explaining high percentage of their variability. A correlation analyses among the main dominant oscillatory modes at decadal 10.2 year (Fig. 6d) and inter-annual frequencies 6.2 year (Fig. 6e) and 3.5 year (Fig. 6f) of the precipitation reconstruction and the SSTs_N3 with 12.7 year, 5.6 year and 3.6 year, respectively, showed in the three cases significant negative correlations.
By
High percentage of the variability in the recorded precipitation reconstruction and the SSTs_N3 is dominated by oscillations modes at decadal (Fig. 6d) and inter-annual (Fig. 6e,f) frequencies. Correlation analyses among the main dominant oscillatory modes of the precipitation reconstruction and the SSTs_N3 at decadal (Fig. 6d) and inter-annual (Fig. 6e,f) ferquencies, showed significant negative correlations. These results highlight the occurrence of common waveforms and demonstrate the ENSO signal in the precipitation reconstruction from the northern South American Altiplano.
Line 367-371. “The phrasing of this doesn't make sense. please clarify”
Original text: The wettest year recorded in our reconstruction is 1876, which is associated with the occurrence of a prolonged cool phase of the central tropical Pacific during 1870–1876 period (La Niña conditions), being the year 1876 the coldest SST record (Singh et al., 2018). This cool La Niña phase conditions reversed to a warm SSTs during the strong 1876/1877 El Niño event (Singh et al., 2018), which is registered in our precipitation reconstruction as an extreme dry year in 1877.
There was a dating error. The Niño event occurred during calendar years 1877/78 (Singh et al. 2018) and not in 1876/77 as stated in the original text. Therefore, the occurrence of the 1877/78 Niño event coincides with the occurrence of an extreme drought event recorded in the 1877 year of our reconstruction. The year 1877 of our reconstruction represents the months corresponding to November and December 1877 and January 1878.
We have changed the date in the new version of the manuscript
Line 380-383. “Can you give actual numbers here - this isn't the best phrasing and has also appeared immediately before”.
The following sentence was rephrased for clarity:
It is important to place this increase in aridity conditions since the late 20th century -beginning 21st century observed in our northern record in the long-term context and the great spatial coherence and synchrony shown by all the other proxies records across the southern tropical Andes (Fig. 7 and Fig. S2), suggesting largescale common atmospheric and ocean forcings over this Andean region
By
In the context of the last four centuries of hydroclimatic variability provided by our reconstruction, the severe aridity conditions since the late 20th century are unprecedented. Due to its large spatial extent and temporal synchronicity, this extraordinary dry event across the Altiplano appears to be modulated by the action of large-scale atmospheric and oceanic forcings common to the entire region
Line 419-422. “Sentence too long and too complex. Please rephrase and clarify.”
Segura et al. (2020) based on instrumental-satellite precipitation data for the southern region of the tropical Andes (12º-20º S; 60º-80º W), evaluate the common pattern of summer rainfall variation for this region during the period 1982-2018, identifying a positive trend specially based in positive anomalies after 2010 that would be influenced by upward motion over the western Amazon.
To be clearer and shorter, we split the sentence as follow:
Segura et al. (2020) based on instrumental-satellite precipitation data for the southern region of the tropical Andes (12º-20º S; 60º-80º W), evaluate the common pattern of summer rainfall variation for this region during the period 1982-2018. They identified a positive trend especially after 2010, which would be influenced by upward motion over the western Amazon.
All typos have been corrected in the new version of our manuscript.
-
AC2: 'Reply on RC2', Mariano Morales, 29 Dec 2022
Status: closed
-
RC1: 'Comment on cp-2022-37', Anonymous Referee #1, 25 May 2022
Dear authors, I read your paper with interest since the topic is super relevant to the dendroclimatology field.
I understand that your main point is to defend the idea of an increased dryness conditions in your study area, based on a tree-ring precipitation reconstruction, however I’m not completely sold on this idea, and you show a brief discussion about it at the end of your discussion in which you mention there are studies (one at least), that show an opposite trend for the same time period, over your study area.
I think one of the key messages would be why would we value the tree-ring based reconstruction of precipitation you are offering over the instrumental data that are currently available. You mention the other paleoclimate proxies, however they have problems like trends that are difficult to remove sometimes.
I raise a few points here, see if you find it interesting to address them.
Abstract:
Lines 35-40: I missed a little explanation of what would be the influences of ENSO in the precipitation in your study area.
In Methods you mention in “Climate data collection and analysis” that you used stations with less than 10% missing data. Why did you make the average of the 7 stations? Did you analyze each station against your chronologies? Or against your regional chronology? Did you try gridded data too?
In line 197, did you try monthly correlations too? I’m confused, did you calculate the average of the entire year?
In line 221, is this your best correlation result? What period is this correlation?
In line 253 you say “stable”, however I think you are comparing this ~ 20 years frequency with the increased frequency you observe in the 20-21th centuries, is that correct? Stable to me sounds like nothing was happening, however it was, but at a lower frequency. I suggest you change the text in this paragraph, there is no such a thing as stable in climate, because it is constantly changing.
In lines 345-347 I ask myself, what are the odds of your chronologies showing decreased growth due to increased temperature and not exactly related to decrease in ppt?
In line 370 you mention 1876/1877, and according to your dated chronology, your 1876 ring is the one that started in November of 1876 and extended to 1877. That would be already when the El Nino happened, and yet you say your 1876 shows as the wettest year.
In line 385 I would suggest you write what BT stands for, I know you already showed in methods, but it’s a long way for the readers to go back and find the abbreviation.
In paragraph 409-416: What is the main source of precipitation in the study area? Is it the Pacific Ocean or the glaciers? Is this drying trend related to losses in ice cover, increased temperature, or both, and are you suggesting increased SST’s activity?
In lines 424-427 you say that these differences in trends could be related to distinct time span, however the instrumental ppt data you are using are also showing negative trend, in opposite to the study published by Segura et al. 2020, is that correct? And in your study, the instrumental data you are also relatively short (~1970-present). Therefore I was asking about why you decided to calculate the average of the 7 stations, even when they had missing data.
Overall, I think this is a great manuscript, the analysis and methodology were well performed. I raised a few questions to you here that I hope can help this narrative. I do think it would be ideal to include more explanation regarding the hydroclimatology in the area, like where does the water come from and the possible explanations for this drying trend.
Below are a few typos I noticed.
Small changes/typos
Introduction:
Line 68: “found”
Line 73: I think you mean to say “by the end of the 2st century”
Line 78-79: I would suggest you only say “changes” instead of “possible current changes”
Line 102: “…the minimum temperature is…”
In “2.7 ENSO signals in the northern Altiplano precipitation” there is a typo when you write NDJ. Right now is written as “NJD”
Discussion
Line 331: “allows”
-
AC1: 'Reply on RC1', Mariano Morales, 05 Sep 2022
Dear editor Keely Mills,
Please, find attached our responses to the reviewer 1 comments on our submission to Climate of the Past, entitled “Drought increased since the mid-20th century in the northern South American Altiplano revealed by a 389-year precipitation record”.
We have prepared a new version of the manuscript that addresses most of the comments from the reviewer. In preparing this new version, we have included the two figures that were in the SI to the main text. Figure S1 is now part of Figure 2, while Figure S2 is now Figure 8.
We thank the reviewer for their thoughtful critiques and his time and consideration.
Kind Regards,
Mariano Morales (corresponding author)
-
AC1: 'Reply on RC1', Mariano Morales, 05 Sep 2022
-
RC2: 'Comment on cp-2022-37', Anonymous Referee #2, 06 Dec 2022
The paper by Morales et al presents a tree-ring precipitation reconstruction from the northern South American Altiplano that spans the last c. 400 years. The study fills a knowledge gap in the region, whilst simultaneously complementing existing work that has been undertaken a broader scale. I am not a technical expert, so cannot comment on the statistical methodology employed for this paper. In terms of the scientific quality and the "story" from start to finish, this is a very neat and comprehensive piece of research which will be valuable to a range of researchers working on hydroclimate variability in South America. The unique record will add value to disciplines beyond dendrochronology and climate reconstructions - it will be of use to the broader palaeo community and also the archaeological community. The authors often cite the issue of water stress and how this can inform management - and this is alluded to in the text at several points. It could be useful for the authors to articulate exactly how their study can be used in management. It would provide context, but as written can not inform management of water supplies. Perhaps more articulation (in a few sentences) could be included in the discussion section of this paper. Overall the quality of the science and the manuscript is very high. There are a few areas where sentences are a little long, and need to be shortened and/or rephrased to make sure the information is not lost. I attach an annotated manuscript with corrections / edits for the authors to undertake.
-
AC2: 'Reply on RC2', Mariano Morales, 29 Dec 2022
We thank the reviewer for their thoughtful critiques and his time and consideration.
General comments
“The authors often cite the issue of water stress and how this can inform management - and this is alluded to in the text at several points. It could be useful for the authors to articulate exactly how their study can be used in management. It would provide context, but as written can not inform management of water supplies. Perhaps more articulation (in a few sentences) could be included in the discussion section of this paper. Overall the quality of the science and the manuscript is very high. There are a few areas where sentences are a little long, and need to be shortened and/or rephrased to make sure the information is not lost. I attach an annotated manuscript with corrections / edits for the authors to undertake.”
To be more specific about the importance of paleoclimatic records as a source of information potentially useful for decision-makers, we rephrase the following paragraph in the Discussion section:
Droughts are of particular relevance in climate variability for this semi-arid region of the Andes. Therefore, the information provided by this study allows us to understand that mean dry condition dominates the instrumental period and the frequency of occurrence of extreme drought events in the present has no precedent in the past. Under a global warming context, the Altiplano's water resources are fundamental for biodiversity conservation and socioeconomic activities. The projected increase in evapotranspiration as a result of global warming, together with a wide range of variability among the precipitation models projected for the 21st century, may lead to growing demand for water in a region already under water stress. Knowing the long-term hydroclimatic variability in this region, we need to consider whether the current configuration of social and organizational structures are sufficient to provide the resilience and adaptation to successfully address current and future hydroclimatic changes. A better understanding of the future of Altiplano's water resources should be listed as priority for stakeholders and decision-makers to avoid social conflicts at both the local and regional levels. Under this complex political, social and environmental scenario, the results from our study are relevant to plan and implement adaptive strategies to reduce these vulnerabilities in the face of future water shortages.
Specific comments
Line 24. “There are several very long sentences in this abstract. I have tried to split some where possible. Please check that sentences are a little bit shorter - it makes it easier to read.”
The abstract and manuscript were revised in order to shorten, where possible, very long sentences.
Line 29. “CLARIFY - this would need rephrasing - it doesn't quite make sense. What gap? Temporal? Spatial? In our knowledge of hydroclimatic change?”
To be clearer, we rephrase the following sentence:
However, in the northern sector of the Peruvian and Chilean Altiplano (16º-19º S) still exist a gap of hydroclimatic tree-ring records.
By
However, in the northern sector of the Peruvian and Chilean Altiplano (16º-19º S) still exist a gap in our knowledge of high-resolution hydroclimatic change based on tree-ring records.
Line 99 – 102. Do you mean >85% of the rainfall occurs from December to March? If so, you need to clarify this. If not, then it will need to be clarified as I'm not sure I understand. “Can you give actual numbers here - this isn't the best phrasing and has also appeared immediately before”
Thanks for the comment. We rephrase and split the sentence to be shorter and clearer.
The climate is semi-arid with dry-cold winters and rainy-warm summers, with a total annual precipitation that ranges between 290-400 mm. More than 85% of the total annual precipitation occurs during summer (December to March).
Line 300-302. “This description doesn't make sense. Can you rephrase”
To be clearer, we rephrase the following sentence:
Strong correlations (r > -0.42) were recorded centered in the periods 1885-1900, 1940-1955, 1965-1975, while sharp decreases in correlations were found centered in the periods 1910-1935, 1978-2000 (Fig. 6c).
by
Strong negative correlations were recorded centered in the periods 1885-1900, 1940-1955, 1965-1975, while a lost in the relationships was found centered in the periods 1910-1935, 1978-2000 (Fig. 6c).
Line 303-307. “Not sure this makes sense. What explains the high percentage. Need to split sentence into 2 and clarify.”
The following sentence was rephrased:
Both, reconstructed precipitation and SSTs_N3 recorded dominant oscillations modes at decadal (Fig. 6d) and inter-annual (Fig. 6e,f) frequencies explaining high percentage of their variability. A correlation analyses among the main dominant oscillatory modes at decadal 10.2 year (Fig. 6d) and inter-annual frequencies 6.2 year (Fig. 6e) and 3.5 year (Fig. 6f) of the precipitation reconstruction and the SSTs_N3 with 12.7 year, 5.6 year and 3.6 year, respectively, showed in the three cases significant negative correlations.
By
High percentage of the variability in the recorded precipitation reconstruction and the SSTs_N3 is dominated by oscillations modes at decadal (Fig. 6d) and inter-annual (Fig. 6e,f) frequencies. Correlation analyses among the main dominant oscillatory modes of the precipitation reconstruction and the SSTs_N3 at decadal (Fig. 6d) and inter-annual (Fig. 6e,f) ferquencies, showed significant negative correlations. These results highlight the occurrence of common waveforms and demonstrate the ENSO signal in the precipitation reconstruction from the northern South American Altiplano.
Line 367-371. “The phrasing of this doesn't make sense. please clarify”
Original text: The wettest year recorded in our reconstruction is 1876, which is associated with the occurrence of a prolonged cool phase of the central tropical Pacific during 1870–1876 period (La Niña conditions), being the year 1876 the coldest SST record (Singh et al., 2018). This cool La Niña phase conditions reversed to a warm SSTs during the strong 1876/1877 El Niño event (Singh et al., 2018), which is registered in our precipitation reconstruction as an extreme dry year in 1877.
There was a dating error. The Niño event occurred during calendar years 1877/78 (Singh et al. 2018) and not in 1876/77 as stated in the original text. Therefore, the occurrence of the 1877/78 Niño event coincides with the occurrence of an extreme drought event recorded in the 1877 year of our reconstruction. The year 1877 of our reconstruction represents the months corresponding to November and December 1877 and January 1878.
We have changed the date in the new version of the manuscript
Line 380-383. “Can you give actual numbers here - this isn't the best phrasing and has also appeared immediately before”.
The following sentence was rephrased for clarity:
It is important to place this increase in aridity conditions since the late 20th century -beginning 21st century observed in our northern record in the long-term context and the great spatial coherence and synchrony shown by all the other proxies records across the southern tropical Andes (Fig. 7 and Fig. S2), suggesting largescale common atmospheric and ocean forcings over this Andean region
By
In the context of the last four centuries of hydroclimatic variability provided by our reconstruction, the severe aridity conditions since the late 20th century are unprecedented. Due to its large spatial extent and temporal synchronicity, this extraordinary dry event across the Altiplano appears to be modulated by the action of large-scale atmospheric and oceanic forcings common to the entire region
Line 419-422. “Sentence too long and too complex. Please rephrase and clarify.”
Segura et al. (2020) based on instrumental-satellite precipitation data for the southern region of the tropical Andes (12º-20º S; 60º-80º W), evaluate the common pattern of summer rainfall variation for this region during the period 1982-2018, identifying a positive trend specially based in positive anomalies after 2010 that would be influenced by upward motion over the western Amazon.
To be clearer and shorter, we split the sentence as follow:
Segura et al. (2020) based on instrumental-satellite precipitation data for the southern region of the tropical Andes (12º-20º S; 60º-80º W), evaluate the common pattern of summer rainfall variation for this region during the period 1982-2018. They identified a positive trend especially after 2010, which would be influenced by upward motion over the western Amazon.
All typos have been corrected in the new version of our manuscript.
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AC2: 'Reply on RC2', Mariano Morales, 29 Dec 2022
Mariano S. Morales et al.
Mariano S. Morales et al.
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