Mountain regions are hydrologically important given the estimate that over one-sixth of the world's population derive the majority of their water resources from basins containing seasonal snowmelt. In fact, in many semi-arid regions, urban and agricultural areas rely almost exclusively on snowmelt runoff from regional mountainous areas. Despite their importance, these regions of complex terrain are often poorly simulated using regional climate models (RCMs). Improvement in understanding land-atmosphere interactions in complex terrain is a key step toward improving the predictions of RCMs in montane regions. The primary objective of this project is to study land-atmosphere interactions in complex terrain with an emphasis on those areas where snow plays a significant role. The project will address science questions using the wealth of data from the Cold Land Processes Field Experiment (CLPX) site that took place in northern Colorado (2002-2003). The proposed research will use a hierarchical approach to investigate snow process and coupled land-atmosphere interactions across a range of physiographic characteristics. Such an approach will allow for explicit representation of surface heterogeneity in not only topography, but in surface states (e.g., snow, albedo), radiative fluxes, and turbulent fluxes, as well as their impacts on 3D boundary layer flow and cloud formation. Several science questions will be addressed in the areas of process understanding (both snow and coupled land-atmosphere processes), spatial variability (as a function of physiography) and how it impacts land-atmosphere interactions, and uncertainty in surface states/fluxes and how this uncertainty propagates within the coupled system. This work will move the state of knowledge regarding processes in mountainous terrain forward with cross-connections to many related disciplines including snow hydrology, mountain meteorology, boundary-layer processes, and computational fluid dynamics. The broader impacts of this project derive from the importance of understanding land-atmosphere interactions in mountainous terrain in order to yield improved predictions of states and fluxes in large-scale climate models, both for near-term forecasts and climate change analysis. It is hypothesized that the insight gained in this project will ultimately prove useful for improving sub-grid scale parameterizations in large-scale models in mountainous terrain, which would be useful to a broad group in the research community.
