Duque Gardeazábal, Nicolás (2025). Some sources of hydroclimate and renewable energy variability in tropical South America. (Thesis). Universität Bern, Bern
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Abstract
Tropical South America (SAm) has significant physical and biological resources. SAm’s hydroclimate variability influences its ecosystems, hydropower, and food and water security, yet the mechanisms controlling these variations are not completely understood. This thesis investigates how a chain of physical processes, induced by ocean–atmospheric modes, modulate SAm’s hydroclimatic variability and the potential solar and wind energy. It also explores how external aerosol forcing influences the mechanisms and afterwards SAm’s rainfall. Chapter 2 examines how Atlantic modes of variability influence SAm’s Evapotranspiration, a key variable for the carbon cycle. Using reanalysis and satellite data, our study identifies how the Atlantic Meridional Mode (AMM) and the Atlantic Niño (Atl3) affect the regional atmospheric circulation and other variables in the chain. Results show that the impacts of the modes are seasonally and geographically different. The AMM-related anomalies of soil moisture, radiation and evapotranspiration migrate from eastern South America during austral autumn toward western Orinoco by austral spring. These impacts are caused by meridional wind anomalies. The Atl3 exerts more localised impacts in the Guianas and eastern Orinoco through changes in pressure and trade winds. The Atlantic modes alter the water and energy cycles in different regions compared to El Niño–Southern Oscillation (ENSO). Chapter 3 focuses on the implications of the altered chain for solar and wind energy production. Considering climate variability into energy planning and storage strategies is relevant to achieve the energy transition to a decarbonised world. We use composites and partial correlations to investigate how ENSO, AMM, and Atl3 influence wind and solar capacity factors across three energy hubs: the North Caribbean, Eastern Brazil, and the Andes (Peru/Bolivia). ENSO-induced sea level pressure anomalies, which modify winds, moisture divergence and radiation, while Atlantic variability generates cross-equatorial wind and cloud anomalies that impact the energy hubs. Our study also investigates the complementarity between the two renewable sources. It found limited complementarity between wind and solar energy at interannual scales. Chapter 4 addresses long-term hydroclimatic variability by comparing the impacts of anthropogenic and volcanic aerosols on the chain of processes and on SAm’s rainfall. Using historical reanalyses, observations, and a paleo-reanalysis, the study shows that anthropogenic aerosols progressively reduced the interhemispheric temperature gradient, displacing the Hadley circulation southward and also rainfall. In contrast, volcanic aerosols are primarily associated with an overall reduction in rainfall, with some eruptions linked to meridional displacements of precipitation. Our results can lead to better predictions of droughts, floods, and renewable energy variability. They can help build or strengthen early-warning systems and support adaptation strategies in a region highly vulnerable to extreme weather events.
| Item Type: | Thesis |
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| Dissertation Type: | Cumulative |
| Date of Defense: | 24 November 2025 |
| Subjects: | 500 Science > 550 Earth sciences & geology |
| Institute / Center: | 10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR) 08 Faculty of Science > Institute of Geography |
| Depositing User: | Hammer Igor |
| Date Deposited: | 05 Dec 2025 14:20 |
| Last Modified: | 05 Dec 2025 14:20 |
| URI: | https://boristheses.unibe.ch/id/eprint/6949 |
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