South America possesses the greatest latitudinal extent of any continent, stretching from 12°N to 56°S. This vast range, combined with the presence of the Andes and dominant ocean currents, creates a mosaic of climates ranging from the world’s wettest tropical rainforests to its driest deserts.
Major Climate Control Factors
The Andes Mountain Range
Acting as a colossal wall, the Andes create distinct rain-shadow effects. In the tropical north, they force moist Amazonian air to rise (orographic rainfall). In the south, they block westerly winds from the Pacific, creating the arid Patagonian Steppe.
Ocean Currents
- The Humboldt (Peru) Current: A cold-water current that flows north along the western coast, cooling the air and stabilizing it, which prevents rainfall and creates the Atacama Desert.
- The Brazil Current: A warm-water current flowing south along the eastern coast, bringing moisture and humidity to the Atlantic forests and coastal Brazil.
Atmospheric Pressure Systems
- Intertropical Convergence Zone (ITCZ): Moves seasonally, dictating the “wet” and “dry” seasons in the northern half of the continent.
- South Pacific and South Atlantic Highs: These semi-permanent high-pressure cells influence wind patterns and aridity.
South American Climate Regions (Köppen-Geiger Classification)
Tropical Rainy (Af) and Monsoon (Am)
- Region: The Amazon Basin, coastal Colombia, and parts of the Guianas.
- Characteristics: High temperatures (averaging 27°C) and heavy rainfall throughout the year (often exceeding 2,500 mm).
- Trivia: The Chocó region in Colombia is one of the wettest inhabited places on Earth.
Tropical Wet and Dry / Savanna (Aw)
- Region: The Orinoco Basin (Llanos) of Venezuela/Colombia and the Brazilian Highlands (Cerrado).
- Characteristics: Distinct alternating wet and dry seasons. The landscape is dominated by grasses and drought-resistant trees.
Arid and Semi-Arid (BWh, BWk, BSh)
- Region: The Atacama (Coastal Chile/Peru), the Sechura (Peru), and the Patagonian Desert (Argentina).
- Characteristics: Extremely low precipitation. The Atacama is hyper-arid, while Patagonia is a “cold desert” due to its high latitude and rain-shadow position.
Humid Subtropical (Cfa) and Mediterranean (Csb)
- Region: Central Chile (Mediterranean); Southeastern Brazil, Uruguay, and the Argentine Pampas (Subtropical).
- Characteristics: * Mediterranean: Dry summers and mild, wet winters (perfect for viticulture).
- Humid Subtropical: Evenly distributed rainfall and hot summers, supporting the continent’s most productive agriculture.
Alpine / Highland (H)
- Region: The Andean peaks.
- Characteristics: Climate varies vertically rather than horizontally. This is categorized by “Altitudinal Zonation.”
Altitudinal Zonation in the Andes
As altitude increases, temperature drops, creating distinct ecological and climatic zones utilized for different types of agriculture.
| Zone | Altitude (Meters) | Climate Type | Major Crops/Activity |
| Tierra Caliente | 0 – 750 | Tropical | Bananas, Sugar Cane, Cacao |
| Tierra Templada | 750 – 1,800 | Temperate | Coffee, Corn, Wheat |
| Tierra Fría | 1,800 – 3,600 | Cool | Potatoes, Barley, Quinoa |
| Tierra Helada | 3,600 – 4,500 | Cold/Frost | Livestock (Llamas/Alpacas) |
| Tierra Nevada | Above 4,500 | Permanent Snow | No Agriculture |
Key Climatic Phenomena for UPSC
El Niño Southern Oscillation (ENSO)
This periodic warming of the central and eastern Pacific waters significantly alters South American weather.
- Impact on Peru/Ecuador: Causes catastrophic flooding and collapses the fishing industry due to suppressed upwelling of nutrients.
- Impact on Brazil: Leads to severe droughts in the Amazon and Northeast Brazil.
The “Flying Rivers”
This term refers to the vast quantities of water vapor transported by winds from the Amazon rainforest to the central-south regions of South America (including the Pantanal and the Pampas). The forest acts as a biological pump, and deforestation directly threatens the rainfall patterns of the continent’s “breadbasket.”
The South Atlantic Anomaly (SAA)
While not a weather phenomenon, this is a “climatic” concern for satellites. It is a spot where Earth’s inner Van Allen radiation belt comes closest to the surface over South America, causing increased radiation levels.
Summary of Regional Climatic Distribution
- The North: Dominated by the ITCZ; predominantly tropical and humid.
- The West: Dominated by the Andes and the cold Humboldt current; results in a thin strip of desert transition into alpine tundra.
- The East: Influenced by the warm Brazil current; ranges from tropical savanna to temperate grasslands.
- The South: Influenced by the Roaring Forties (westerly winds) and the Antarctic influence; temperate to sub-polar climates.