TOPOGRAPHIC AND CLIMATIC CONTROLS ON PRECIPITATION IN MOUNTAIN BELTS

Precipitation plays a central role in the erosion of mountain ranges, but the links between topography, climate, precipitation, and erosion remain enigmatic. Several previous studies have used simple linear parameterizations of orographic precipitation to probe the sensitivities of the coupled atmospheric-topographic system, but orographic precipitation is a profoundly nonlinear process; linear models may therefore not capture the full sensitivity of the system. Here we use an idealized but fully nonlinear atmospheric model to explore how changes in topography and climate influence precipitation in mountain ranges. The results show a remarkable sensitivity to changes in topography. In the model configuration used here, changes in topography of 200 m can induce a doubling of precipitation over uplifting topography and can cut downstream precipitation in half. Furthermore, the results show that uniform changes in atmospheric conditions (driven by global climate change, for example) may produce significantly non-uniform changes in precipitation across mountain ranges. The implications of these results for erosion in mountain belts will be discussed.