At their closest, Africa and South America are separated by less than 3000 km. The African continent provides a strong heat source near the equator, extending well into the Northern Hemisphere during boreal summer. The Amazon heating maximum also provides a heat source during austral summer, but with different vertical structure and a somewhat smaller horizontal scale. Dynamical theory suggests that such large-scale heat sources will force circulation responses on space scales of thousands of kilometers. This study is aimed at understanding the role of the African heat source in determining the South American precipitation climatology, and vice versa.

Several GCM simulations are analyzed to isolate the mechanisms of the intercontinental teleconnection. These include simulations with Africa alone, South America alone, and Africa and South America together. We find that, in general, Africa has a stronger influence on South America than South America has on Africa. During boreal summer, for example, the presence of the African heat source generates a subsidence anomaly over the central equatorial Atlantic Ocean. This subsidence forces low level divergence in the central Atlantic, strengthens the moisture advection onto the South America continent, and increases precipitation rates. Precipitation over the Nordeste region of Brazil is especially sensitive to the circulation anomalies associated with the presence of Africa.