Micrometeorology: theory and measurements of ground-air exchange

微气象学：地气交换的理论和测量

• 批准号: RGPIN-2015-03776
• 负责人: Wilson, John
• 金额: $ 2.4万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=684836
• 关键词: Micrometeorology; theory; measurements; ground; air

My research is focused on the lowest (roughly) 100 m of the atmosphere, a layer known as the atmospheric surface layer ("ASL"), and which exerts a crucial control over many facets of our lives and activities (e.g. downwind spread of pesticide sprays). The most consequential impact of my program has been the invention, testing and application of a simple, non-intervening method ("bLS") for the estimation of ground-air gas emissions that can be applied at the "whole farm" level (e.g. ammonia emissions from a cattle feedlot). The capability to determine such fluxes is important because  in some jurisdictions emissions limits are in force, or pending; our new technique is already popular in many countries. At the Greenhouse Gases and Animal Agriculture conference in Banff (Oct., 2010) I gave an invited workshop on bLS for estimating methane emissions, and of the more than 400 delegates from some 38 countries attending, 160 registered for the bLS workshop. ***I propose the following (connected) lines of research, in relation to ground-air exchange:***a) My group has evolved a sensitive new method for determining the ground-air flux by sequentially directing a light beam along upward- and downward-slanting paths over the source. I shall support graduate students to measure methane, ammonia and nitrous oxide fluxes in relation to cattle management and genetic variability. This will train students in both the instrumental and theoretical elements of the technique.***b) A "Lagrangian stochastic" (LS) turbulent mixing model is central to the "bLS" flux measurement technique, for it is used to compute the movement of gas backwards (in time and space) from detector to source. Though the LS model is the state-of-the-art theory for environmental mixing, it is not a finished work. With students I have made numerous contributions to theory of the LS model, and propose to continue doing so. We will establish whether a recent proposal extending the famous "Langevin model" (originally used to explain Brownian motion) usefully applies to wind transport in the turbulent ASL. ***c) Wind speed and direction vary with height, and our bLS method adopts idealized profiles (due to Monin & Obukhov). However site imperfections (e.g. uneven terrain) compromise this assumption. The student will determine to what extent fluxes inferred by bLS become inaccurate, due to winds deviating from the MO profiles.***d) Flux instruments sample a nearby region of upwind surface, known as the "flux footprint," which it is vital to be able to compute. Existing formulae employ a mathematical trick, using "power laws" to represent the height (z) profiles of wind speed and (other variables) instead of the correct (Monin & Obukhov) laws. This makes existing formulae ambiguous. We will develop an alternative "footprint model" based on correct profiles of wind speed and eddy diffusivity, by extending a method of Wilson (1982, Boundary-Layer Meteorol. 23, 85-103).**

我的研究集中在最低（大约）100米的大气层，这一层被称为大气表面层（“ASL”），它对我们生活和活动的许多方面都有至关重要的控制（例如农药喷洒的顺风传播）。我的项目最重要的影响是发明、测试和应用了一种简单的、无干预的方法（“bLS”）来估计地面空气中的气体排放，这种方法可以应用于“整个农场”水平（例如，养牛场的氨排放）。确定这种通量的能力很重要，因为在一些司法管辖区，排放限制已经生效或即将生效；我们的新技术已经在许多国家受到欢迎。2010年10月，在班夫举行的温室气体和畜牧业会议上，我应邀举办了一个关于估算甲烷排放的劳工统计局的研讨会，来自38个国家的400多名代表参加了该研讨会，其中160人注册参加了劳工统计局研讨会。关于地面-空气交换，我提出以下（相连的）研究方向：***a)我的小组已经发展出一种灵敏的新方法，通过在光源上方沿向上和向下倾斜的路径依次引导光束来确定地面-空气通量。我将支持研究生测量与牛管理和遗传变异有关的甲烷、氨和一氧化二氮通量。这将训练学生在这一技术的工具和理论元素。***b)“拉格朗日随机”（LS）湍流混合模型是“bLS”通量测量技术的核心，因为它用于计算气体从探测器到源的反向（在时间和空间上）运动。虽然LS模型是最先进的环境混合理论，但它还没有完成工作。与学生一起，我对LS模型的理论做出了许多贡献，并建议继续这样做。我们将确定最近提出的扩展著名的“朗格万模型”（最初用于解释布朗运动）的建议是否有效地适用于湍流ASL中的风输送。***c)风速和风向随高度而变化，我们的bLS方法采用了理想化的廓线（由于Monin & Obukhov）。然而，场地的不完美（例如，不平坦的地形）损害了这一假设。由于风偏离MO剖面，学生将确定由bLS推断的通量在多大程度上变得不准确。***d)通量仪器对迎风表面附近的区域进行采样，称为“通量足迹”，这对于能够计算至关重要。现有的公式采用了一种数学技巧，使用“幂定律”来表示风速和（其他变量）的高度(z)剖面，而不是正确的（莫宁和奥布霍夫）定律。这使得现有的公式变得模棱两可。我们将通过扩展Wilson（1982，边界层气象，23,85-103）的方法，开发一种基于正确风速和涡流扩散率剖面的替代“足迹模型”