Orographic barriers, high‐resolution TRMM rainfall, and relief variations along the eastern Andes

TLDR

Tectonic and erosive processes shape mountain landscapes, yet climatic, sedimentary, and tectonic dynamics limit high relief at the Andean front, reducing pronounced rainfall peaks. The study investigates how tectonic and erosive interactions influence rainfall patterns along the humid eastern Andes, focusing on relief as a primary predictor. Using high‑resolution TRMM and SRTM data, the authors map elevation, relief, and hillslope angle at peak rainfall sites along orographic barriers. Across 3500 km of the eastern Andes, peak rainfall (>3.5 m yr⁻¹) occurs at ~1.3 km elevation, ~0.95 km relief, and ~18° hillslope, confirming relief as the strongest rainfall predictor and showing its variation south of the Andean orocline.

Abstract

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.