Foehn Dynamics - Lagrangian Analysis and Large-Eddy Simulation

Foehn Dynamics - 拉格朗日分析和大涡模拟

• 批准号: 411621386
• 负责人: Professor Dr. Juerg Schmidli, Ph.D.
• 金额: --
• 依托单位: Institut für Atmosphäre und Klima
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/411621386?language=en
• 关键词: Foehn; Dynamics; Lagrangian; Analysis; Large

This project considers some of the key problems of Foehn research: the origin and warming mechanisms of the Foehn air, the descent of Foehn into the northern valleys and displacement of the cold air pool, the variability of the mechanisms for different Foehn flavors, and the accuracy of Foehn flows in NWP models. More specifically, the aims are: (i) The detailed Lagrangian analysis of Foehn air warming and of the scrambling of air masses will be extended to several (distinct flavors of) Foehn flows, hence assessing the impact of microphysical processes on warming and scrambling; additionally, the heat budget of the air parcels along the Foehn trajectories will include heating due to turbulence and radiation; (ii) The origin of the Foehn air in the valleys will be assessed by labeling and then transporting a passive tracer in the NWP model; in particular, the initial altitude of the air parcels on the Alpine south side will be used as a tracer. This kind of analysis will extend existing studies on the vertical evolution of Foehn air before it passes over the Alpine crest. As an additional benefit, labeling air masses above the Alpine crest and later determining their relative contribution in the Foehn valleys allows the degree of downward mixing to be quantified; (iii) Eulerian analysis of heat, moisture and momentum budgets and large-eddy simulations (LES) will be performed for selected Foehn valleys, resulting in a better understanding of the land-atmosphere coupling between Foehn air and the surface, in a clearer picture on how these processes influence the displacement (erosion) of the initial cold pools, and in a better understanding of the weaknesses and strengths of current and recently developed parameterizations of these processes in the NWP model used; (iv) The analyses planned for the selected case studies will, with a reduced degree of detail, be extended over a climatological time scale of (potentially) 10 years. To this aim, the analysis tools will be coupled to a novel approach in NWP simulations and analysis (Sinergia project crCLIM), where the NWP simulation and analysis tools run in parallel and communicate with each other by means of a data virtualization layer. The project will extensively use hindcast simulations of Foehn cases by the COSMO NWP model. The high- resolution trajectories will be calculated based on these hindcasts. Further, the LES simulations will address the complex flow evolution near the surface. Observational datasets will be used to evaluate the numerical simulations. The Eulerian budget analysis and Lagrangian analysis will complement each other and hence allow for a comprehensive analysis of the Foehn flow. The project will harvest recent methodological advances to shed new light on several long- standing problems in Foehn research and contribute to a better representation of Foehn in NWP models and hence lead the way for improved forecasts of a key high-impact weather phenomenon in Alpine regions.

这个项目考虑了焚风研究的一些关键问题：焚风空气的起源和变暖机制，焚风下降到北方山谷和冷空气池的位移，不同焚风味道的机制的可变性，以及数值预报模式中焚风流动的准确性。更具体地说，目标是：（一）详细的拉格朗日分析焚风空气变暖和混乱的空气质量将扩展到几个焚风流的（不同的味道），因此评估微物理过程对变暖和混乱的影响;此外，沿着焚风轨迹的空气包的热收支将包括由于湍流和辐射引起的加热;（ii）将通过标记并在数值预报模式中输送被动示踪剂来评估山谷中焚风空气的来源;特别是，将使用阿尔卑斯山南侧空气包的初始高度作为示踪剂。这种分析将扩展现有的研究焚风空气的垂直演变之前，它通过阿尔卑斯山的波峰。作为一个额外的好处，标记空气质量以上的阿尔卑斯山波峰，然后确定它们的相对贡献，在焚风谷允许向下混合的程度被量化; ㈢将对选定的焚风谷进行热量、水分和动量收支的欧拉分析和大涡模拟，从而更好地了解焚风空气与地面之间的陆-气耦合，更清楚地了解这些过程如何影响初始冷池的位移（侵蚀），并更好地了解当前和最近开发的NWP模式中这些过程的参数化的弱点和优势; ㈣为选定的个案研究计划进行的分析将减少细节，在气候时间尺度上延长（可能）10年。为此，分析工具将与NWP模拟和分析的新方法（Sinergia项目crCLIM）相结合，其中NWP模拟和分析工具并行运行，并通过数据虚拟化层相互通信。该项目将广泛使用COSMO数值预报模式对焚风个例的后报模拟。高分辨率的轨迹将根据这些后报来计算。此外，LES模拟将解决复杂的表面附近的流动演变。观测数据集将用于评价数值模拟。欧拉预算分析和拉格朗日分析将相互补充，从而允许焚风流的综合分析。该项目将收获最新的方法学进展，为焚风研究中的几个长期存在的问题提供新的认识，并有助于在数值预报模式中更好地代表焚风，从而为改善阿尔卑斯地区关键高影响天气现象的预报开辟道路。