3]) curl with greater intensity in the center of the south Pacific anticyclone, located southeast of the islands.
In effect, the EIP is located approximately equidistant between the center of the subtropical gyre's rotation and the south Pacific anticyclone.
The principal large-scale systems responsible for the variability of precipitation over South America are: the Alta de Bolivia (AB), the South Atlantic Convergence Zone (SACZ), the Intertropical Convergence Zone (ITCZ), the South Pacific Anticyclone
(SPA), and the South Atlantic Anticyclone (SAA).
While the Humboldt Current creates a stable atmosphere, the eastern Pacific anticyclone, a high-pressure cell, determines the patterns of winds that reach the coast.
The Andes desiccate the west coast from 30[degrees] S north almost to the equator, undoubtedly amplifying the effects of the Humboldt Current and the eastern Pacific anticyclone.
Because the flora is shaped largely by the aridity of the region, the study of the area's biogeography is tied to the development of the Humboldt Current, the eastern Pacific anticyclone, and the Andes.
Therefore, the eastern Pacific anticyclone that affects climatic patterns of western South America so strongly probably has been in place since at least the mid-Miocene.
Seasonal and annual variations in precipitation in northern Patagonia (at about 40 [degrees] S) are strongly influenced by changes in the intensity and latitudinal positions of the southeast Pacific anticyclone (Pittock 1973, 1980).
Variation in the southeast Pacific anticyclone and high-latitude atmospheric circulation is also linked to ENSO events (Diaz and Kiladis 1992).
Similar to the association of drought and fire demonstrated here, other studies in northern Patagonia (Villalba and Veblen 1997a, 1998) show that the establishment of seedlings and mortality of adult trees of Austrocedrus are strongly associated with variations in ENSO and in the strength and position of the southeastern Pacific anticyclone.