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

山区气象过程涵盖了广泛的相互作用的尺度，这给数值天气预报带来了挑战。事实上，在山区，例外通常是规则，因为标准理论、测量技术、分析技术和参数化通常不是严格有效的。在这个项目中，我们将试图通过利用我们的团队将部署的新的测量技术来解决这些现有的一些困难，这些技术将用于研究从微观尺度(即湍流耗散尺度O(1 Mm))到中观伽马尺度的物理过程。我们将通过利用野外实验、新开发和最先进的仪器以及坡面流动和吹雪的数值模拟的多方面方法来更好地了解山区地形中的流动物理。*这个项目的主要目标是在野外活动中利用新的仪器技术，并开发新一代数值工具：(I)更好地理解关键的山区地形科学问题和(Ii)改进坡面流动和雪输送的模拟。该项目的主要实验部分将是在瑞士阿尔卑斯山的迪希玛山谷开展实地活动。*山区的近地表过程在与雾形成、森林火灾、积雪融化和空气质量有关的事件中可能特别重要，在这些事件中，为平坦的开阔地形设计的模式通常应用于山区。此外，近地表的动力流动过程对于了解高山地区的积雪输送过程是非常重要的。虽然已经进行了许多出色的现场和数值研究，但仍有许多重要的问题有待回答。在这里，我们的目标是通过有针对性的野外实验，利用专门的仪器和大涡模拟(LES)的新进展来回答这些问题中的一部分。*考虑到这一研究领域的广度，我们将集中精力研究与山区地形近地表过程有关的几个关键科学问题。具体地说，我们将回答以下与山区地形物理过程有关的问题：*1.在陡峭的非均匀山坡上，能否使用新的快速响应仪器来测量潜热和感热通量，并仔细考虑平流和能量储存，从而关闭地表能量收支？*2.控制早晚过渡期间输送动力学的主要物理机制是什么？*3.大气流动中的地表切应力驱动机制是什么？*4.空气运动和雪输送的大涡模拟能可靠地代表基本物理吗？

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.***********