Variability of the Diurnal Cycle of Precipitation in South America

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The analysis of the daily precipitation cycle was carried out on a large spatial scale and undoubtedly took a lot of doing. The procedure for processing IMERG data was explained in a comprehensive manner. The analysis of the data also raises no objections. I would like the authors to make minor corrections and refer to some issues:

1. Figure 1: DCPs on some plots have truncated maximum values, this should be corrected. In addition, the projection of the continent is too stretched out.
2. Lines 78 -81: It would be useful to add, how the utility of IMERG data has been substantiated?
3. Lines 84-86: The data is analyzed in four seasons. Such a division is comfortable for analysis. The important issue seems to be the existence of  four seasons over the whole of Southern America and potential differences of the daily cycle of precipitation between the distinguished seasons. It is also uncertain whether DCP differences are not pronounced at other time intervals in particular areas of Southern America. Please refer to this issue.
4. Line 132 Small typo: "To di this, the elbow method . . ."
5. Discussion: Could there be disturbances in the DCP, intensity of the hourly average precipitation rate in the distinguished seasons associated with ENSO, for example?

Author Response

Comments 1: Figure 1: DCPs on some plots have truncated maximum values, this should be corrected. In addition, the projection of the continent is too stretched out.

Response 1: Thank you for you comment. We agree with your observation. Accordingly, we have revised Figure 1 to ensure that the DCPs plots no longer display truncated maximum values. Additionally, we have adjusted the map projection by adopting the PlateCarree projection in Python, which provides a more accurate representation of the continent's shape. 

Comments 2: Lines 78 -81: It would be useful to add, how the utility of IMERG data has been substantiated?

Response 2: Thank you for your valuable comment. We agree that it is important to justify the use of IMERG data in our analysis. We have now added a brief explanation in lines 78–88 to clarify the utility of IMERG data for studying the variability of the diurnal cycle of precipitation in South America. Specifically, we highlighted previous studies that have validated IMERG’s performance in capturing high-frequency precipitation patterns and Mesoscale Convective Systems across South America. These references support the dataset's suitability for our objectives. (Lines 77-88)

Comments 3: Lines 84-86: The data is analyzed in four seasons. Such a division is comfortable for analysis. The important issue seems to be the existence of  four seasons over the whole of Southern America and potential differences of the daily cycle of precipitation between the distinguished seasons. It is also uncertain whether DCP differences are not pronounced at other time intervals in particular areas of Southern America. Please refer to this issue.

Response 3: Thank you for pointing this out. We agree that such a division doesn't reflect the full diversity of climatic regimes across the continent, particularly in equatorial and tropical regions where seasonal cycles are often defined by wet and dry periods rather than temperature variations. We chose the conventional seasonal periods to facilitate comparison with previous studies and to ensure methodological consistency. We have added a short sentence mentioning the main reason for choosing this division in lines 93-94.

Comments 4: Line 132 Small typo: "To di this, the elbow method . . ."

Response 4: Thank you for pointing out this typographical error. We have corrected the word “di” to “do” in line 132.

Comments 5: Discussion: Could there be disturbances in the DCP, intensity of the hourly average precipitation rate in the distinguished seasons associated with ENSO, for example?

Response 5: Thank you for your insightful comment. Indeed, it is possible that disturbances in the Diurnal Cycle of Precipitation (DCP), particularly in the intensity of the hourly average precipitation rate during different seasons, may be associated with large-scale climate variability phenomena such as ENSO. These disturbances could be related to shifts in the ascending and descending branches of the general circulation, which modulate convection patterns over the region. We briefly mention this possibility in the Summary and Conclusions section of the manuscript. However, we did not conduct a specific analysis to assess the impact of ENSO on the DCP in this study. We recognize this as a relevant and promising direction for future research, and we appreciate the reviewer’s suggestion in this regard. You can find this short mention in the page 24 (lines 810-812). 

All corrections and changes are highlighted in yellow. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a large-scale analysis of the diurnal cycle of precipitation over South America using harmonic analysis and clustering. While the study includes valuable data, issues with structure, clarity, and repetition reduce its overall impact.

Introduction
 - The introduction highlights that the DCP in SA varies significantly from place to place due to complex factors such as topography and local circulations. However, the study aims to identify homogeneous areas where the DCP shows similar patterns. This creates a mismatch: the background emphasizes the variability of the DCP, whereas the goal is to group areas with similar behavior. This change in focus should be explained more clearly so that the reader understands why it makes sense to identify similar regions in a generally variable system.
 - The introduction does not provide enough detail about the choice of methods. It briefly mentions the use of satellite data and diurnal metrics but does not explain why these specific metrics were selected, why the IMERG product was chosen. A clearer justification of these methodological decisions could be added.

Methodology
In general, the methodology is clear, and Figures 1 and 2 explain how the method works. 
In section 2.3, it should be clarified: 
 - n is not clearly defined. Is n = 48?
 - The range of k is not specified. The formulas suggest k ranges up to n⁄2, the study only uses the first two harmonics (k = 1, 2). This could be stated explicitly.
 - Variables t and Yₜ are not properly introduced. Is it true that t refers to time steps within a day and Yₜ represents precipitation rate values at those times?

The schematic diagram A3 would be more effective if included in the main text rather than the appendix, as it helps the reader understand the logical sequence of data processing and analysis steps. This would also allow the main text to be more concise by reducing the need for detailed procedural descriptions. 

Results
The results are relevant but excessively detailed, with significant redundancy that affects readability.

According to the reviewer, what is valuable:
 - Section 3.1 (Climatology…) presents important and well-visualized data (f₀, AN, ϕ) that support the characterization of the diurnal precipitation cycle.
 - Section 3.2 (Regions with a homogeneous DCP) is meaningful for identifying clusters and linking them to physical conditions.
 - Section 3.3 (Trends…) is relevant as it evaluates long-term changes over a 20-year period.

Possible excessive content:
 - There is repetition between sections 3.2, 3.3, and the discussion, with clusters described multiple times in nearly identical language.
 - The lengthy seasonal descriptions for each cluster in section 3.2 follow similar structures and could be condensed into summaries or tables, highlighting only the distinctive cases.
 - Duplicate content:
Phrases like “cluster with AN < 0.5” or “peaks in the afternoon and evening” are repeated many times with minimal variation.
 - The cluster descriptions are very similar and follow the same pattern. They could be grouped more clearly, for example by summarizing tropical clusters with bimodal patterns together.

Recommendation:
Section 3.2 could be shortened by at least half, focusing on general seasonal patterns rather than describing every cluster in detail.
Key features could be presented in a table (cluster number, AN, peak time, region), making the text clearer and more concise.

Discussion
The Discussion section contains significant repetition of the Results and would benefit from greater focus and depth. 
Excessive overlap:
 - Many paragraphs restate what is already shown in the figures and described in the results, often with only minimal additional interpretation.
  - In several places, the location and color of clusters are explained again, despite having been detailed earlier.
 Lack of higher-level interpretation:
 - The discussion often misses broader insights or connections to regional climate processes, comparisons to models, or implications for prediction.
 - Mentions of possible causes (e.g., droughts, deforestation, SAMS) appear briefly and without development.
 
Useful in discussion:
Some parts, such as the discussion on MCS activity and the role of the ALLJ, add value and show understanding of physical mechanisms.
The note that DCP trend analysis is uncommon in previous studies is a strong point that highlights novelty.
 
Summary on discussion:
The current discussion is too descriptive and closely mirrors the results. It should become more analytical and interpretive to add real scientific insight.

Conclusion section
Conclusions are not provided.
A conclusions section is essential in a long study with complex results.

 

Comments on the Quality of English Language

Grammar
In general, the text is well written. 

However, some improvements could be made. 
 - Some sentences are overloaded with information and too long, which affects readability and clarity.
 - There is excessive repetition throughout the text, particularly in the results and discussion sections, which could be significantly reduced without losing essential information.
 - Some language choices and sentence structures could be improved for clarity.
For example:
Line 59: "..continent which is constituted by 13 countries.." --> "...continent, consisting of 13 countries“
Line 60: „SA is delimited in the north by the Caribbean Sea“ --> better is "bordered" when talking about borders of countries.
Line 61: "...in the world and presents strong topographic gradients" --> may be better "features" or "exhibits"
... and so on.

Author Response

Comments 1: 

Introduction
 - The introduction highlights that the DCP in SA varies significantly from place to place due to complex factors such as topography and local circulations. However, the study aims to identify homogeneous areas where the DCP shows similar patterns. This creates a mismatch: the background emphasizes the variability of the DCP, whereas the goal is to group areas with similar behavior. This change in focus should be explained more clearly so that the reader understands why it makes sense to identify similar regions in a generally variable system.
 - The introduction does not provide enough detail about the choice of methods. It briefly mentions the use of satellite data and diurnal metrics but does not explain why these specific metrics were selected, why the IMERG product was chosen. A clearer justification of these methodological decisions could be added.

Response 1:

We thank the reviewer for this thoughtful and constructive comment.

- In response to this concern, we have revised the Introduction to clarify our rationale. While the DCP is indeed modulated by large-scale mechanisms and local factors—such as topography, land-atmosphere interactions, and mesoscale circulations—it is precisely this variability that motivates the need for a systematic identification of areas with coherent diurnal behavior. By grouping regions with similar DCP characteristics, we aim to uncover underlying spatial structures and patterns that may reflect common physical controls. This approach allows for a more organized interpretation of the spatial complexity and facilitates the use of regionalized diagnostics in future modeling and prediction efforts. The revised paragraph in the Introduction now better highlights this point.

IMERG was chosen due to its high temporal resolution (30-minute intervals), which is essential for resolving the structure and timing of the DCP. Moreover, its global coverage and consistent data quality make it suitable for regional comparisons across diverse geographical settings. The selected diurnal metrics---such as the amplitude and phase of the first harmonics----have been widely used in previous studies to characterize the temporal structure of precipitation and are well-suited to capture key aspects of the DCP.

These clarifications have been incorporated into the revised manuscript as suggested. (Lines: 143-156)

Comments 2:

Methodology
In general, the methodology is clear, and Figures 1 and 2 explain how the method works. 
In section 2.3, it should be clarified: 
 - n is not clearly defined. Is n = 48?
 - The range of k is not specified. The formulas suggest k ranges up to n⁄2, the study only uses the first two harmonics (k = 1, 2). This could be stated explicitly.
 - Variables t and Yₜ are not properly introduced. Is it true that t refers to time steps within a day and Yₜ represents precipitation rate values at those times?

The schematic diagram A3 would be more effective if included in the main text rather than the appendix, as it helps the reader understand the logical sequence of data processing and analysis steps. This would also allow the main text to be more concise by reducing the need for detailed procedural descriptions. 

Response 2:

Response to Reviewer:

We thank the reviewer for their positive assessment of the methodology section and for the detailed suggestions to improve clarity.

In Section 2.3, we have made the following clarifications in response to the reviewer’s observations:

• The variable n is now explicitly defined as the number of time steps within a 24-hour period, i.e., n=48, given the 30-minute temporal resolution of the data. (Line 243)

• We have specified that in this study, only the first two harmonics (k = 1, 2) are computed and analyzed. While the general formula allows for k ranging up to n⁄2, we have limited the analysis to these lower-order harmonics to focus on the most dominant components of the diurnal cycle. (Lines 240-241)

• The variables t and F(t) have been properly introduced. We now state that t refers to the time steps within a day (from 1 to n = 48) and F(t) represents the mean precipitation rate at each time step t, for a given latitude and longitude. (Lines 251-252)

Regarding the schematic diagram A3, we appreciate the reviewer’s suggestion. We agree that integrating this figure into the main text would enhance the reader’s understanding of the workflow. Therefore, we have moved it from the appendix to the end of Section 2.5, where it is now referenced directly in the description of the analysis steps. In doing so, we have also slightly streamlined the surrounding text to avoid redundancy and improve overall readability. (Page 9)

We hope these revisions address the reviewer’s concerns and contribute to a clearer and more accessible presentation of the methodology.

Comment 3:

Results
The results are relevant but excessively detailed, with significant redundancy that affects readability.

According to the reviewer, what is valuable:
 - Section 3.1 (Climatology…) presents important and well-visualized data (f₀, AN, ϕ) that support the characterization of the diurnal precipitation cycle.
 - Section 3.2 (Regions with a homogeneous DCP) is meaningful for identifying clusters and linking them to physical conditions.
 - Section 3.3 (Trends…) is relevant as it evaluates long-term changes over a 20-year period.

Possible excessive content:
 - There is repetition between sections 3.2, 3.3, and the discussion, with clusters described multiple times in nearly identical language.
 - The lengthy seasonal descriptions for each cluster in section 3.2 follow similar structures and could be condensed into summaries or tables, highlighting only the distinctive cases.
 - Duplicate content:
Phrases like “cluster with AN < 0.5” or “peaks in the afternoon and evening” are repeated many times with minimal variation.
 - The cluster descriptions are very similar and follow the same pattern. They could be grouped more clearly, for example by summarizing tropical clusters with bimodal patterns together.

Recommendation:
Section 3.2 could be shortened by at least half, focusing on general seasonal patterns rather than describing every cluster in detail.
Key features could be presented in a table (cluster number, AN, peak time, region), making the text clearer and more concise.

Response 3:

We thank the reviewer for the careful reading of the manuscript and for highlighting both the strengths and the opportunities to improve the clarity and conciseness of the Results section.

We appreciate the recognition of the value of Section 3.1, which provides a foundation for the characterization of the diurnal cycle using the selected harmonic metrics, and of Sections 3.2 and 3.3, which offer insights into spatial patterns and temporal trends of the DCP.

In response to the reviewer’s comments regarding redundancy and excessive detail, we have made the following revisions:

• Reduction of redundancy: We have carefully reviewed Sections 3.2, 3.3, and the Discussion to eliminate repeated descriptions of clusters. Where similar content appeared across these sections, we retained the most informative and contextually appropriate instance, and rephrased or removed redundant passages to improve the flow of information. On pages 12 - 23

• Condensation of seasonal descriptions in Section 3.2: We agree that the repeated structure of the seasonal descriptions for each cluster may hinder readability. We have significantly shortened this section by synthesizing similar patterns across clusters and highlighting only distinctive or physically relevant features. Instead of describing each cluster in full detail for every season, we now emphasize the main types of behavior (e.g., bimodal vs. unimodal DCPs, timing peaks) and group clusters accordingly. On pages 12 - 16

• Addition of a summary table: To facilitate a clearer understanding of the main features of each cluster, we have included a new summary table (Table 1 on page 14) that presents, for each cluster: (i) geographical extent, (ii) amplitude (AN), (iii) phase (peak time), and (iv) precipitation rate. This has allowed us to further reduce the narrative length while preserving the essential information. On pages 12 - 16

These changes have reduced the length of Section 3.2 by approximately 50%, as recommended by the reviewer, and we believe they significantly improve the readability and accessibility of the results.

We thank the reviewer once again for this valuable suggestion, which helped enhance the clarity and impact of our presentation.

Comment 4:

Discussion
The Discussion section contains significant repetition of the Results and would benefit from greater focus and depth. 
Excessive overlap:
 - Many paragraphs restate what is already shown in the figures and described in the results, often with only minimal additional interpretation.
  - In several places, the location and color of clusters are explained again, despite having been detailed earlier.
 Lack of higher-level interpretation:
 - The discussion often misses broader insights or connections to regional climate processes, comparisons to models, or implications for prediction.
 - Mentions of possible causes (e.g., droughts, deforestation, SAMS) appear briefly and without development.
 
Useful in discussion:
Some parts, such as the discussion on MCS activity and the role of the ALLJ, add value and show understanding of physical mechanisms.
The note that DCP trend analysis is uncommon in previous studies is a strong point that highlights novelty.
 
Summary on discussion:
The current discussion is too descriptive and closely mirrors the results. It should become more analytical and interpretive to add real scientific insight.

Response:

We thank the reviewer for the detailed and constructive feedback regarding the Discussion section. We appreciate the suggestions to improve its focus and analytical depth, and we have taken several steps to address the points raised:

• Reduction of repetition: We acknowledge that the original version of the Discussion included considerable overlap with the Results section, particularly in the reiteration of cluster locations and characteristics already shown in the figures. In the revised manuscript, we have substantially reduced descriptive repetition and removed references to visual elements that were already thoroughly discussed earlier. This has allowed us to allocate more space to interpretative content.

• Greater analytical depth and broader connections: In response to the suggestion for higher-level interpretation, we have revised the Discussion to explore broader climatic mechanisms and regional processes that may underlie the observed DCP patterns and trends. This includes:

  • A more developed discussion on the influence of the South American Monsoon System (SAMS), and other large-scale mechanisms responsible for the onset of convection in South America.

  • An expanded interpretation of the role of mesoscale convective systems (MCSs), particularly in connection with the low-level jets (ALLJ and SALLJ) and orographic influences.

  • A discussion on land-use changes and deforestation in southern Amazonia and central Brazil as potential drivers of observed DCP modifications, particularly in the amplitude and timing of peak precipitation.

  • Consideration of how these findings compare with outputs from regional and global models, including the challenges that models face in capturing DCP dynamics accurately.

• Reinforcement of novelty: We have also emphasized the novelty of the DCP trend analysis by situating it in the context of the existing literature, which has traditionally focused on total precipitation trends or seasonal means rather than diurnal characteristics.

Comment 5:

Conclusion section
Conclusions are not provided.
A conclusions section is essential in a long study with complex results.

Response:

We agree with the reviewer that a dedicated Conclusions section is essential, especially in a study with complex and multi-faceted results. Accordingly, we have added a concise but comprehensive Conclusions section at the end of the manuscript. This section:

• Summarizes the main findings across the climatology, clustering, and trend analyses.

• Highlights the methodological contributions, particularly the use of harmonic metrics and regionalization by cluster analysis.

• Reflects on the broader implications for understanding precipitation regimes and improving DCP modeling.

• Suggests potential avenues for future research, including the evaluation of model performance and the investigation of ENSO influences on DCP variability.

We believe these additions enhance the scientific contribution of the manuscript and better align the structure with standard practices for studies of this scope.

Comment 6:

Grammar
In general, the text is well written. 

However, some improvements could be made. 
 - Some sentences are overloaded with information and too long, which affects readability and clarity.
 - There is excessive repetition throughout the text, particularly in the results and discussion sections, which could be significantly reduced without losing essential information.
 - Some language choices and sentence structures could be improved for clarity.
For example:
Line 59: "..continent which is constituted by 13 countries.." --> "...continent, consisting of 13 countries“
Line 60: „SA is delimited in the north by the Caribbean Sea“ --> better is "bordered" when talking about borders of countries.
Line 61: "...in the world and presents strong topographic gradients" --> may be better "features" or "exhibits"
... and so on.

Response:

 

We thank the reviewer for the positive overall assessment of the writing and for the specific suggestions to improve grammar, clarity, and style.

In response, we have carefully revised the manuscript to improve sentence structure, reduce redundancy, and enhance readability. We addressed the overlong sentences and simplified constructions where needed. The suggested corrections (e.g., lines 59–61) were implemented, and similar expressions throughout the text were also reviewed and refined accordingly.

Corrections and changes made are highlighted in green throughout the text.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The reviewed manuscript fits into the subject area of ​​the journal. The title of the manuscript corresponds to its content. The stated research goal has been achieved. The issues have been presented in a clear and logical manner. The content included in the manuscript has been divided into chapters and subchapters in an appropriate manner. For the clarity of the text (Point 2.1 (page 3, figure1)) I suggest marking the cited countries (page 2 line 59-60) and the names of the main rivers (e.g. line 567-568, line 621, line 638) and cited states (e.g. page 13 line 397-398 – ‘…French Guiana and the Brazilian states of Amapá and Pará…’, line 647), in Figure 1. Research material: the manuscript assumes precipitation from the period 2001-2020 (page 2 line 50, page 3 line 71) - I suggest adding information why a 20-year period has been adopted and not a longer one, e.g. 30 years (1991-2020). The reviewed manuscript thematically concerns precipitation, therefore I suggest enriching point ‘2.1 Study area’ with a short description of precipitation in the study area. The methodology is clearly described in this detailed explanation of ‘Identification of homogeneous regions’. I suggest adding Figure A3 to the main body of the manuscript. Although the body of the manuscript provides the literature of the included tests (Mann-Kendall test, Sen’s slope method – page 6 line 152-153), in their case I suggest providing the appropriate formulas. Figure 7, figure 8, figure 9 – figure title – I suggest changing it, because the significance level is 5%, and the confidence level is 95% (page: 14, 15, 16 – ‘…with significant trends at the 95% significance level’).

A detailed discussion of the results was carried out, adding conclusions that result from the content of the manuscript. There is a lack of point ‘conclusion’, I suggest adding a separate point ‘5 Conclusion’. The cited literature refers to the research topic. The obtained results are supported by figures. The drawings included in the manuscript are legible and clearly described. The explanations of the abbreviations used in the manuscript are noteworthy, which definitely makes the manuscript clear.

Author Response

Comments 1:  For the clarity of the text (Point 2.1 (page 3, figure1)) I suggest marking the cited countries (page 2 line 59-60) and the names of the main rivers (e.g. line 567-568, line 621, line 638) and cited states (e.g. page 13 line 397-398 – ‘…French Guiana and the Brazilian states of Amapá and Pará…’, line 647), in Figure 1.

Response 1: We thank the reviewer for this helpful suggestion to improve the clarity of Figure 1 by adding geographical references mentioned throughout the manuscript.

In response, we have updated Figure 1 to include:

• The names of the 13 South American countries, as cited in the Introduction (page 2, lines 59–60);

• The main rivers referenced in the Results and Discussion sections (e.g., Amazon, Madeira, São Francisco, Tocantins);

• The names of regions such as the Brazilian states of Amapá and Pará, and French Guiana, as mentioned in lines 397–398 and 647.

These additions help to contextualize the spatial analyses and improve geographic orientation for the reader. The revised figure is now more informative and aligned with the textual references throughout the manuscript. You can see these changes on page 5.

Comment 2: Research material: the manuscript assumes precipitation from the period 2001-2020 (page 2 line 50, page 3 line 71) - I suggest adding information why a 20-year period has been adopted and not a longer one, e.g. 30 years (1991-2020).

Response 2: We thank the reviewer for this relevant observation regarding the time period adopted in the study. We have chosen the 2001–2020 period primarily due to the availability and consistency of the IMERG precipitation dataset, which begins in mid-2000, with full global coverage and stable algorithm versions available only from 2001 onward. This ensures a homogeneous and high-quality data record suitable for climatological and trend analyses. You can see these changes in lines 73-75.

Although a 30-year period (e.g., 1991–2020) is often recommended for climatological studies, the high temporal resolution and spatial coverage required for analyzing the diurnal cycle are not available with consistent quality before 2001. Thus, using a longer period would introduce inconsistencies due to data heterogeneity and reduced comparability.

Comment 3: The reviewed manuscript thematically concerns precipitation, therefore I suggest enriching point ‘2.1 Study area’ with a short description of precipitation in the study area.

Response 3: We thank the reviewer for this valuable suggestion to enhance the Study Area section with precipitation-related information. In response, we have enriched Section 2.1 by including a brief description of the mean annual precipitation across South America based on the 2001–2020 period. This information is now also visually represented in the updated Figure 1, which includes the spatial distribution of total annual precipitation. Additionally, we have included the mean annual precipitation cycle for selected locations representative of distinct climatic regimes within the study area. These additions provide important context for understanding the regional variability of precipitation patterns and support the motivation for analyzing the diurnal precipitation cycle. You can see these updated in lines 178 - 208. 

Comment 4: The methodology is clearly described in this detailed explanation of ‘Identification of homogeneous regions’. I suggest adding Figure A3 to the main body of the manuscript. Although the body of the manuscript provides the literature of the included tests (Mann-Kendall test, Sen’s slope method – page 6 line 152-153), in their case I suggest providing the appropriate formulas.

Response 4: We thank the reviewer for the constructive suggestions.

In response, Figure A3 has already been moved to the main body of the manuscript and is now presented at the end of the Methodology section, as recommended (page 9). We agree that this inclusion improves the clarity of the methodological workflow.

Regarding the Mann-Kendall and Sen’s slope tests, we appreciate the reviewer’s suggestion to include their formulas. However, to maintain the conciseness of the Methods section and avoid redundancy, we have opted not to include the equations directly in the text, as the tests are already well-established in the literature and properly cited. We believe the current references offer sufficient guidance for readers seeking detailed formulations.

Comment 5: Figure 7, figure 8, figure 9 – figure title – I suggest changing it, because the significance level is 5%, and the confidence level is 95% (page: 14, 15, 16 – ‘…with significant trends at the 95% significance level’).

Response 5: We thank the reviewer for pointing out the inconsistency in the figure titles regarding the significance and confidence levels. The captions for Figures 7, 8, and 9 (now Figure 8, 9, and 10) have been revised to correctly state that the trends shown are statistically significant at the 5% significance level (equivalent to a 95% confidence level). We appreciate the attention to detail, which helped improve the accuracy of the manuscript.

Comment 6: There is a lack of point ‘conclusion’, I suggest adding a separate point ‘5 Conclusion’.

Response 6: 

We agree with the reviewer that a dedicated Conclusions section is essential, especially in a study with complex and multi-faceted results. Accordingly, we have added a concise but comprehensive Conclusions section at the end of the manuscript. This section:

• Summarizes the main findings across the climatology, clustering, and trend analyses.

• Highlights the methodological contributions, particularly the use of harmonic metrics and cluster analysis-based regionalization.

• Reflects on the broader implications for understanding precipitation regimes and improving sub-daily precipitation modeling.

• Suggests potential avenues for future research, including the evaluation of model performance and the investigation of ENSO influences on DCP variability.

We believe these additions enhance the scientific contribution of the manuscript and better align the structure with standard practices for studies of this scope.

Corrections and changes made are highlighted in orange throughout the text.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

About one third of the Section 4-Discussion is devoted to the mean precipitation rate, their spatial distribution, large-scale atmospheric mechanisms and processes, such as the South American Monsoon System or Intertropical Convergence Zone. But the goal and title of the paper, first of all, concern the diurnal cycle, not the mean precipitation. Some of this part could be transferred to the 1.Introduction as a general description of precipitation patterns in South America.

Homogeneous clusters defined by diurnal metrics are described in the Section 3-Results in very detail depending on various characteristics examined. As expected, clusters will be enumerated and generalized in the Section 4-Discussion, but they are cited just as examples of different atmospheric processes influence.

It is also desirable to emphasize what is the novelty with regard to earlier works mentioned in the 1-Introduction and what DCP peculiarities have been not discovered by in-situ weather stations versus IMERG product.

Author Response

Comment 1: About one third of the Section 4-Discussion is devoted to the mean precipitation rate, their spatial distribution, large-scale atmospheric mechanisms and processes, such as the South American Monsoon System or Intertropical Convergence Zone. But the goal and title of the paper, first of all, concern the diurnal cycle, not the mean precipitation. Some of this part could be transferred to the 1.Introduction as a general description of precipitation patterns in South America.

Response 1: We thank the reviewer for this insightful comment. In response, the focus of the Discussion section has been revised to emphasize the diurnal metrics that characterize the Diurnal Cycle of Precipitation (DCP) and their relationship with large-scale and local-scale physical mechanisms. General descriptions of mean precipitation patterns and related atmospheric processes have been reduced or relocated to the Introduction, where they now serve as contextual background for the study. We appreciate the suggestion, which helped us improve the structure and thematic coherence of the manuscript (lines 538 - 561).

Comment 2: Homogeneous clusters defined by diurnal metrics are described in the Section 3-Results in very detail depending on various characteristics examined. As expected, clusters will be enumerated and generalized in the Section 4-Discussion, but they are cited just as examples of different atmospheric processes influence.

Response 2: We thank the reviewer for the valuable observation. As suggested, the Discussion section was revised to provide a more generalized synthesis of the homogeneous clusters defined by diurnal metrics, rather than repeating detailed descriptions. Clusters are now discussed in relation to the atmospheric processes that influence their diurnal behavior (Lines 663 - 699). Additionally, a summary table (page 14) was included to present the key characteristics of each cluster—such as geographic location, peak precipitation time, type of diurnal distribution, and mean precipitation rate. This table facilitates a clearer and more concise presentation of the cluster properties and supports the interpretive discussion. We appreciate the suggestion, which significantly improved the clarity and organization of the manuscript.

Comment 3: It is also desirable to emphasize what is the novelty with regard to earlier works mentioned in the 1-Introduction and what DCP peculiarities have been not discovered by in-situ weather stations versus IMERG product.

Response 3:  We thank the reviewer for this important suggestion. In response, the Introduction section was revised to better highlight the main novelties of the present study in relation to previous works. We now explicitly discuss the advantages of using the IMERG satellite-based product over in-situ weather stations, particularly in terms of its higher spatial and temporal resolution, which enables a more comprehensive and continuous characterization of the diurnal cycle of precipitation (DCP) across remote and data-sparse regions of South America. These improvements strengthen the justification for the methodological choices adopted in the study and help clarify its contribution to the current body of knowledge on DCP variability. (Lines 142 - 156)

Corrections and changes made are highlighted in blue throughout the text.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made a significant effort to improve the manuscript. One of the main comments in the first review was the repetition and duplication of the text. Unfortunately, the revised version still contains these issues. Such length may fail to reach or engage the intended reader.

Introduction.
Although the revised introduction responds to the reviewer’s earlier comments, the introduction is too long. It should be shortened by removing unnecessary literature, clearly explaining the choice of metrics, and presenting the study’s aim more directly.

Methodology
Given the manuscript’s overall length, the methodology section should also be shortened. 
–  shorten Section 2.1 (“Study area”); it’s background, not methods.
– Reduce excessive literature in the data section.
– Avoid repeating metric definitions (f₀, C₁, AN); explain once.
– Add brief transitions between subsections to improve flow.

Results
The revised Results section has some improvements, but key issues remain. 
– Still too long: the text is overly detailed and exceeds what is needed to support the visuals.
– Repetitive descriptions: same regions and values are described multiple times across seasons.
– Redundant with figures: much of the text narrates what is already shown graphically.
– Missing summary sentences: subsections end without clear conclusions or takeaways.
Recommendation: significantly reduce length, avoid repeating figure content, and add brief summaries per subsection.

Discussion
– Excessive length: discussion contains too many details, reducing clarity and readability.
– Repetitiveness: several parts reiterate previously presented results.
– Overdescription: extended explanations weaken the focus on key interpretations.
– Lack of structure, no final paragraph summarizes the main insights, difficult to follow: high text density makes it hard to identify central messages.
Recommendation: reduce length, organize content by key topics and key findings.

Conclusions
 – The conclusions are unusually long
– Some content repeats methods or detailed results, which belong more appropriately in the results section.
– There is a lack of a concise summary – the key messages are buried in excessive detail.
Recommendations:
– Shorten to 3–5 paragraphs.
– Remove repetitive information (e.g., definitions of IMERG or harmonics).
– Focus on key points: what was discovered, why it matters, and what should be studied next.

Author Response

Comments 1:

Introduction.
Although the revised introduction responds to the reviewer’s earlier comments, the introduction is too long. It should be shortened by removing unnecessary literature, clearly explaining the choice of metrics, and presenting the study’s aim more directly.

Response 1:

We share the reviewer’s perspective regarding the length and density of the Introduction section. However, the inclusion of additional background literature and contextual information was made in response to specific suggestions from other reviewers. Therefore, we prefer to wait for their updated comments before making further revisions to ensure consistency across all suggestions.

That said, we appreciate the reviewer’s recommendation and are fully open to modifying the section to improve its clarity and flow in the final version of the manuscript.

Comments 2:

Methodology
Given the manuscript’s overall length, the methodology section should also be shortened. 
–  shorten Section 2.1 (“Study area”); it’s background, not methods.
– Reduce excessive literature in the data section.
– Avoid repeating metric definitions (f₀, C₁, AN); explain once.
– Add brief transitions between subsections to improve flow.

Response 2: (Pages 4 to 9)

Methodology Section

We appreciate the reviewer’s suggestions regarding the length and focus of the Methodology section. In response:

• Section 2.1 (Study Area): Additional information on annual total precipitation and its seasonal cycle was incorporated following suggestions from other reviewers, with the aim of highlighting precipitation variability across the study domain. We acknowledge the reviewer’s recommendation to shorten this subsection. However, we prefer to wait for feedback from the remaining reviewers before deciding whether to retain or relocate this content. If necessary, we are open to transferring this material to the Supplementary Information.

• Data section: The number of cited references has already been reduced to avoid excessive literature.

• Metric definitions: Repetitions of diurnal metrics (f₀, C₁, AN) were removed, and each metric is now defined only once in a concise manner.

• Transitions: Brief transitions have been added between subsections to improve the flow and readability of the text.

We thank the reviewer for these constructive observations, which have contributed to a more concise and coherent presentation of the methodology.

Comments 3:

Results
The revised Results section has some improvements, but key issues remain. 
– Still too long: the text is overly detailed and exceeds what is needed to support the visuals.
– Repetitive descriptions: same regions and values are described multiple times across seasons.
– Redundant with figures: much of the text narrates what is already shown graphically.
– Missing summary sentences: subsections end without clear conclusions or takeaways.
Recommendation: significantly reduce length, avoid repeating figure content, and add brief summaries per subsection.

Response 3: (Pages 9 - 18)

Results section

We thank the reviewer for the insightful recommendations to improve the clarity and conciseness of the Results section. In response to these suggestions:

• We have reduced the overall length of the section by removing overly detailed descriptions and avoiding unnecessary repetition of regions and values across seasons.

• We have eliminated redundancies with the figures by streamlining the narrative and focusing on key findings rather than reiterating graphical content.

• We have added concise summary sentences at the end of each subsection to emphasize the main takeaways and improve the logical structure of the section.

We appreciate the reviewer’s contribution to improving the readability and scientific communication of this manuscript.

Comments 4: 

Discussion
– Excessive length: discussion contains too many details, reducing clarity and readability.
– Repetitiveness: several parts reiterate previously presented results.
– Over description: extended explanations weaken the focus on key interpretations.
– Lack of structure, no final paragraph summarizes the main insights, difficult to follow: high text density makes it hard to identify central messages.
Recommendation: reduce length, organize content by key topics and key findings.

Response 4: (Pages 18 - 22)

We appreciate the reviewer’s thoughtful feedback on the structure and clarity of the Discussion section.

In response, we have revised and reorganized the section following the reviewer’s recommendations:

• The content has been condensed, reducing unnecessary detail and repetition of previously presented results.

• The structure was improved by dividing the discussion into clearly defined subsections organized by key topics and findings, facilitating a more logical flow and readability.

• A final summarizing paragraph has been added to highlight the main insights and conclusions derived from the analysis.

These changes were made with the goal of strengthening the interpretative focus and improving the overall clarity of the discussion. We thank the reviewer for the valuable suggestions.

Comments 5:

Conclusions
 – The conclusions are unusually long
– Some content repeats methods or detailed results, which belong more appropriately in the results section.
– There is a lack of a concise summary – the key messages are buried in excessive detail.
Recommendations:
– Shorten to 3–5 paragraphs.
– Remove repetitive information (e.g., definitions of IMERG or harmonics).
– Focus on key points: what was discovered, why it matters, and what should be studied next.

Response 5: (Pages 22 - 23)

We thank the reviewer for the constructive suggestions to improve the Conclusions section.

Following the recommendations:

• The section has been substantially shortened and now consists of 3–5 concise paragraphs.

• We have removed repetitive content, including methodological details and definitions (e.g., IMERG, harmonic components), which were already addressed in previous sections.

• The revised version now focuses on the key findings, their scientific relevance, and suggestions for future research.

We agree that these changes have significantly improved the clarity and impact of the concluding remarks, and we are grateful for the reviewer’s guidance in this regard.

Author Response File: Author Response.pdf