the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 Nov 2024
An Atlantic influence on evaporation in the Orinoco and Amazon basins
Abstract. Tropical South America’s hydroclimate is influenced by ocean-atmospheric oscillations. The physical mechanisms that tele-connect the Atlantic modes of variability with the soil moisture and evaporation of the region remain unclear. This study uses composites of reanalysis and satellite data to identify the processes linking land-surface anomalies and ocean modes. It shows that the Atlantic Meridional Mode (AMM) generates cross-equatorial wind anomalies that affect moisture convergence, in turn modifying the cloud cover, precipitation, radiation availability and hence evaporation. The anomalies have important geographical differences depending on the analysed season; they migrate from the east in Austral autumn towards central Amazon and western Orinoco in Austral spring. The Atlantic El Niño (Atl3) affects the Guianas and eastern Orinoco by means of pressure and trade wind variability. Evaporation is water- or energy-driven depending on the position of the Intertropical Convergence Zone (ITCZ), but the anomalies are controlled by the phase of each mode which alter water and radiation availability. Both Atlantic modes mainly impact regions different from those impacted by El Niño Southern Oscillation (ENSO), although northeast Brazil and the Guianas might experience overlapping effects. Therefore, these ocean-atmospheric modes impact the water and energy cycles and might influence regional climate extremes (e.g. droughts and floods), and are critical for achiving sustainable development (SDG).
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2024-2846', Anonymous Referee #1, 12 Dec 2024
The manuscript investigates the reasons behind the link between the Atlantic Meridional Mode and the Atlantic El Nino Equatorial mode in Tropical South America. Subobjectives include determining the drivers of evaporation and establishing the sequence of physical mechanisms linking modes to anomalies.
I appreciate the wide use of resources and data to address the objectives and the nice figures used to do so. It is also commendable to explain the chain of atmospheric processes that explain evapotranspiration. Although I do not have major concerns with the scientific approach and its validity, the manuscript in its current state is convoluted, hard to read, and lacks a clear direction. First, the reasoning behind the need to understand the "chain" of mechanisms is not clear, nor is there a need to find all these correlations. Why are they needed in the first place? This even affects the potential reviewer's assessment regarding the scientific approach.
To explain to the authors what I mean, I opted to supply an attachment with comments where I consider that the manuscript fails to explain the purpose, aim, and methods to the reader. The introduction does not correctly identify a knowledge gap; if it does, it is not based on a robust literature review that sets the state-of-the-art. When I arrived at the three objectives at the end of the introduction, I noticed that little background was given to justify them was not much related to them. Furthremore, the subobjectives do not relate to each other. What are the key research questions that you want to be answered? Is there a hypothesis that wants to be tested? How is the manuscript advancing the current literature? It is unclear why "the teleconnection of the Atlantic modes of variability with the soil moisture and evaporation of the region remains unclear" in the literature.
The number of acronyms used and the lack of explanation of the reasoning for conducting the methods also make it hard to judge or even read the results. I recommend the results be divided into several additional sections that may independently address each objective. This is especially necessary for section 4.2., which is too repetitive and complex to understand. The figures are also complex; they have too much information and acronyms. I recommend opening these figures and analyzing each of the panels separately.
Finally, I believe that most readers of HESS do not have sufficient knowledge to understand the paper. Many evident and necessary definitions of terms for the study are missing, making it difficult for the paper to understand. Conclusions should also be directly and explicitly related to your objectives of questions.
- AC1: 'Reply on RC1', Nicolas Duque-Gardeazabal, 23 Jan 2025
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RC2: 'Comment on egusphere-2024-2846', Anonymous Referee #2, 20 Dec 2024
- AC2: 'Reply on RC2', Nicolas Duque-Gardeazabal, 23 Jan 2025
Interactive computing environment
Codes for "An Atlantic influence on evaporation in the Orinoco and Amazon basins" Nicolas Duque-Gardeazabal https://github.com/nduqueg/ET_var_SAme
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