Land-atmosphere Interaction over complex terrain: Hydrology and Large Eddy Simulation

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Mountain meteorological processes cover a wide range of interacting scales that introduce challenges for numerical weather prediction. In fact, in mountainous regions, exceptions are often the rule in the sense that standard theories, measurement techniques, analysis techniques, and parameterizations are usually not strictly valid. In this project, we will attempt to attack some of these existing difficulties by taking advantage of new measurement techniques that our team will deploy to study physical processes over scales ranging from the microscale (i.e., dissipation scales of turbulence, O(1mm)) into the meso-gamma scale. We will gain improved understanding of flow physics in mountainous terrain through a multifaceted approach utilizing field experiments, newly developed and state-of-the-art instrumentation and numerical simulations of slope flows and blowing snow.******The major aims of this project are to utilize novel instrumentation techniques in field campaigns and develop new generation numerical tools for: (i) improved understanding of critical mountain terrain science issues and (ii) improved simulations of slope flows and snow transport. The main experimental part of the project will be a field campaign to be conducted in the Dischma Valley of the Swiss Alps. ******Near surface processes in mountainous terrain can be particularly important in events related to fog formation, forest fires, snowmelt, and air quality, where models designed for flat open terrain are often applied over mountainous regions. In addition, near surface dynamical flow processes can be extremely important in understanding snow transport processes in alpine terrain. While many excellent field and numerical studies have been conducted, there are still a number of open important questions that remain to be answered. Here, we aim to answer a subset of those questions through targeted field experiments with specialized instrumentation and new developments in Large Eddy Simulation (LES) for slope flows and snow transport over snow/ice surfaces.******Given the breadth of this research area, we will focus our efforts on several key scientific questions related to near surface processes in mountain terrain. Specifically, we will look to answer the following questions related to physical processes in mountain terrain:***1. Can the surface energy budget be closed on steep heterogeneous mountainous slopes using new fast response instruments for measuring latent and sensible heat fluxes and carefully accounting for advection and energy storage?***2. What are the dominant physical mechanisms governing transport dynamics during morning and evening transition periods?***3. What mechanisms drive surface shear stress in atmospheric flows?***4. Can LES simulations of air movement and snow transport reliably represent the underlying physics.***********