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规模，引入数值天气预报的挑战。事实上，在山区，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，在这个意义上，例外往往是规则。在这个项目中，我们将试图利用新的测量技术来解决这些现有的困难，我们的团队将部署这些技术来研究从微观尺度（即，湍流耗散尺度，O（1 mm））到中伽马尺度。我们将通过多方面的方法，利用现场实验，新开发的和最先进的仪器和斜坡流和吹雪的数值模拟，提高对山区流动物理学的理解。 该项目的主要目标是利用新的仪器技术在现场活动和开发新一代的数值工具：（一）提高对关键的山区地形科学问题的理解和（二）改进模拟的坡面流和雪运输。该项目的主要实验部分将是在瑞士阿尔卑斯山的Dischma山谷进行的实地活动。 在与雾形成、森林火灾、融雪和空气质量相关的事件中，山区地形的近地表过程可能特别重要，其中为平坦开阔地形设计的模型通常应用于山区。此外，近地面动力流过程可以是非常重要的，在了解高山地形的雪输送过程。虽然已经进行了许多出色的实地和数值研究，但仍有一些开放的重要问题有待回答。在这里，我们的目标是回答这些问题的一个子集，通过有针对性的现场实验，专门的仪器和新的发展，在大涡模拟（LES）的斜坡流和雪运输雪/冰表面。 鉴于这一研究领域的广度，我们将把我们的努力集中在几个关键的科学问题，在山区地形近地表过程。具体而言，我们将寻求回答以下与山区地形物理过程相关的问题： 1.使用新的快速响应仪器测量潜热和感热通量，并仔细考虑平流和能量储存，在陡峭的异质山坡上，地表能量收支是否可以关闭？ 2.在早晨和傍晚的过渡期，控制输送动力学的主要物理机制是什么？ 3.什么机制驱动大气流动中的表面剪应力？ 4.大涡模拟的空气运动和雪的运输可靠地代表了基本的物理。

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.