Overview of South American climate

South America extends from equatorial to subpolar latitudes and consequently experiences a wide diversity of climate, governed by remarkably complex meteorological phenomena. Most of the continent, however, is within the tropics. On the continent are three arid regions, the Atacama-Peruvian Desert along the west coast and the Monte and Patagonian deserts east of the Andes in the south (Fig. 15.1). A number of other regions are classified as semi-arid, including areas surrounding the Monte and Patagonian deserts, northeastern Brazil, the high-altitude Puna, the woodlands and thorn forest of the Espinal and Chaco, and the northern Caribbean coast of Venezuela and Columbia. Subhumid environments include the Pampas grassland and parts of the Brazilian savanna.

The major characteristics of South American climate are a function not only of the general atmospheric circulation, but also of the steep and narrow Andean cordillera spanning its full north–south extent and of the geographic characteristics of the Southern Hemisphere (see below). The Andes have a strong impact on transient disturbances and low-level atmospheric circulation (Seluchi et al. 2006). As in North America, this north–south mountain barrier precludes the strong development of true maritime climates, except in the south. It also produces a mosaic of climates, with isolated dry valleys in enclosed basins only some 100 km away from subtropical forests (Mares et al. 1985). Because of the relatively small latitudinal expanse of most of South America, both the Pacific and Atlantic Oceans have a strong influence on the continent. The maritime influence is particularly strong in the mid- and high latitudes.