Climate Variability and Precipitation Patterns in South America
Summary
South America exhibits a complex tapestry of precipitation regimes shaped by interactions between large-scale circulation systems, regional topography and oceanic variability. The South American monsoon system governs seasonal rainfall over the continent, with moisture transported from the Amazon basin towards the Andes via the South American Low-Level Jet (SALLJ). Orographic lifting along the Andes induces steep precipitation gradients, producing humid eastern slopes and arid rain shadows to the west. Interannual fluctuations are largely driven by the El Niño–Southern Oscillation, which modulates sea surface temperatures and redirects moisture pathways, while intraseasonal influences such as the Madden–Julian Oscillation generate bursts of convective rainfall. Decadal variability arises from modes such as the Atlantic Multidecadal Oscillation and the Southern Annular Mode, imprinting multiyear shifts in precipitation patterns across the Altiplano and the Pantanal. Recent warming trends have intensified extreme events, leading to more frequent droughts and floods with profound implications for water security, agriculture and biodiversity. Understanding these interconnected drivers is critical for refining seasonal forecasts, improving resilience and informing sustainable management of South America’s vital hydroclimate.
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Climate Variability and Precipitation Patterns in South America publication trend
The graph below shows the total number of articles in climate variability and precipitation patterns in south america across all publications each year (not limited to Nature Index journals).
Technical terms
South American Low-Level Jet (SALLJ): A narrow corridor of strong easterly winds along the eastern Andes that transports moisture from the Amazon basin and modulates precipitation.
El Niño–Southern Oscillation (ENSO): A coupled ocean-atmosphere phenomenon in the tropical Pacific that drives interannual climate variability and alters rainfall distribution across South America.
Rossby wave train: Large-scale meandering atmospheric waves that propagate along midlatitude jet streams, linking remote sea surface temperature anomalies to continental precipitation patterns.
Madden–Julian Oscillation (MJO): A tropical intraseasonal oscillation characterised by eastward-moving convective envelopes that influence rainfall across the Americas on 30–60-day timescales.
Orographic lifting: The ascent of moist air over mountain slopes, causing adiabatic cooling and enhanced precipitation on windward flanks.
References
- The South America Low-Level Jet: form, variability and large-scale forcings. npj Climate and Atmospheric Science (2023).
- The 2022-23 drought in the South American Altiplano: ENSO effects on moisture flux in the western Amazon during the pre-wet season. Weather and Climate Extremes (2024).
- Untangling the importance of dynamic and thermodynamic drivers for wet and dry spells across the Tropical Andes. Environmental Research Letters (2023).
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