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[1] Quantifying the degree to which tectonic and erosive processes shape landscapes is key to understanding the evolution of tectonically active mountain belts. Here we explore the interplay of these two processes along the humid, eastern flank of the South American Andes. We use high-resolution Tropical Rainfall Measurement Mission (TRMM) and SRTM data to characterize elevation, relief, and hillslope angle of peak rainfall at orographic barriers. Over a distance of more than 3500 km along the eastern flanks, we find that peak rainfall (>3.5 m/yr) occurs at a mean elevation of 1.3 ± 0.17 km, a mean relief of 0.95 ± 0.08 km, and at moderate mean hillslope angles of 18.3 ± 1.7°. We suggest that topographic relief is the best first-order rainfall predictor and we demonstrate how relief changes along strike south of the Andean orocline alter rainfall distribution. Changes in climatic, sedimentary, and tectonic processes prevent the formation of high relief amounts at the mountain front and these areas are not characterized by pronounced rainfall peak. Citation: Bookhagen, B., and M. R.Strecker (2008), Orographic barriers, high-resolution TRMM rainfall, and relief variations along the eastern Andes, Geophys.

The history of the southern central Andes, including the world's second largest plateau and adjacent intermontane basins and ranges of the Eastern Cordillera and the northern Sierras Pampeanas of Argentina and Bolivia, impressively documents the effects of tectonics and topography on atmospheric circulation patterns, the development of orographic barriers, and their influence on erosion and landscape evolution at various timescales. Protracted aridity in the orogen interior has facilitated the creation and maintenance of the Puna-Altiplano plateau. Contraction and range uplift, filling of basins, and possibly wholesale uplift of the plateau increased gravitational stresses in the orogen interior, which caused the eastward migration of deformation into the foreland and successive aridification. The uplift of the Andean orogen has also had a far-reaching influence on atmospheric and moisture-transport patterns in South America. This is documented by the onset of humid climate conditions on the eastern side of the Andes in late Miocene time, which was coupled with the establishment of dramatic precipitation gradients perpendicular to the orogen, and changes in tectonic processes in the Andean orogenic wedge.

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