One of the most enduring challenges in the Earth Sciences, existing their inceptions as fields of study, has been to understand the balance of forces acting to sculpt the landscape around us. Intuitively, it is clear that climate plays a role ? one simply has to witness a powerful river at high stage, or to see the debris curtain of rock laid out in front of a glacier. Moreover, seeing a cloud-draped mountain from afar, it is easy to understand that the role that topography itself plays in weather. It is only in recent years that quantitative tools have been brought to bear on studying the mutual interactions between atmospheric and erosional processes.
This proposal tackles aspects of this challenge in one of the best settings available ? the Olympic Mountains of Washington State. A unique seven-year archive of high-resolution output from an operational numerical weather prediction model is available. It is a very sophisticated tool for diagnosing in detail the response of atmospheric flow to the topography and the consequences for the pattern of precipitation. Seven years covers a wide variety of synoptic conditions, but the pattern is remarkably persistent. For the last four years the group has operated a dense network of precipitation gauges able to evaluate this modeled pattern. Support from this grant will add automated weather stations to this network, and maintain it in the field for another three years. Hydrological models routinely convert these precipitation patterns into river discharge. Their output can be evaluated from stream flow gauges. On geologic time scales these patterns in river discharge translate into patterns of surface erosion that ultimately act to shape the mountain range itself. The second part of this proposed research will combine the latest understanding of what controls fluvial erosion and land-sliding with the understanding of the spatial and temporal patterns of precipitation gained from the meteorological analyses.
Broader Impacts. This work tackles a highly interdisciplinary challenge, of the sort that is the future of the Earth Sciences. The goals of the research are of interest to anyone who has hiked in the mountains and been curious about how such things came to be. The proposed work also has concrete relevance for assessment of landslide hazards, and the research group regularly engages with school children in an economically-deprived area about this work.
