DevelopmentsinEarthSurfaceProcesses ...

Climate and Geomorphologic-related Disasters in Latin America 9
is a northwest-southeast-oriented band of enhanced precipitation that extends from
the Amazon Basin to the Atlantic Ocean (Fig. 1.1 and Fig. 1.4b). The SAMS is also
characterized by strong easterly winds that carry warm, moist air from the tropical
Atlantic into the Amazon Basin. Upon reaching the Andes Mountains, this easterly
air current turns southward, flowing along the Andes Mountains (Gandu and Geisler
1991) forming a circulation feature known as the South American low-level jet
(SALLJ; Fig. 1.1 and Fig. 1.4b). The SALLJ provides the warm humid air that fuels
precipitation along the SACZ. During the SAMS season Central America, Venezuela,
Chile, and southern Argentina remain notably dry.
Important local maxima of annual rainfall amounts occur at the mouth of the
Amazon River and in the western Amazon Basin (Fig. 1.5). The wettest region in
all of Latin America occurs near the border of Colombia and Panama. The
Colombian town of Andagoya (5N, 76W) is among the wettest places on Earth,
with annual rainfall amounts of over 6800 mm. In contrast, one of the driest places
on Earth is the town of Arica, Chile, where years can go by without a drop of rain
falling from the sky.
The main dry regions of South America can easily be seen in the mean annual
rainfall shown in Figure 1.5. In a typical year, the sinking air motion produced by
the South Pacific high-pressure system allows little rain to fall in the coastal areas of
Peru and Chile from the equator to 30°S. The presence of the Andes Mountains
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Figure 1.5 Average total annual rainfall (mm) from the GPCP dataset.
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