Collaborative Research: Up-scaling from Leaf to Canopy the Aerosol-sized Particle Collection Mechanism Within a Non-uniform Canopy Medium

合作研究：将不均匀冠层介质中气溶胶大小的颗粒收集机制从叶子扩大到冠层

• 批准号: 1102309
• 负责人: Sara Pryor
• 金额: $ 56.81万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-15 至 2015-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1102309&HistoricalAwards=false
• 关键词: Collaborative; Research; Up; scaling; Leaf

Atmospheric aerosol particle concentrations represent one the largest uncertainties in understanding of both historical and possible future climate forcing, and even regional atmospheric chemistry models exhibit considerable discrepancies with in situ observations of particle size distribution and composition in part because of the complexities of particle dynamics, including dry deposition. Given the expansive forest cover and relatively high particle deposition velocities over forests, the role of forested ecosystems in removing aerosol particles is drawing increased attention in a number of scientific disciplines and regulatory agencies. However, significant uncertainties remain due to: (1) difficulties associated with field measurements of particle size resolved fluxes and mean concentrations, (2) lack of detailed and simultaneous measurements of the canopy medium and, more importantly, foliage surface characteristics, and (3) challenges in describing all the main features of the transporting agent (turbulence) within and immediately above the canopy. This project will address three key aspects of particle deposition onto forested surfaces using a combined experimental and modeling approach at multiple hierarchical scales (leaf-to-canopy) by exploring: (1) the relative importance of, and correct descriptions of, the foliage collection mechanisms at the leaf scale, (2) deposition flux partitioning between foliar and non-foliar elements, and (3) up-scaling results from aspects [1] and [2] to the entire ecosystem.Canopy scale size-resolved particle fluxes and mean concentration profiles will be measured in a diverse array of forested sites (conifers and broadleaf) endowed with "idealized" micrometeorological conditions and in controlled experiments in an environmental chamber. Findings from these experiments will guide the development of new particle collection schemes at the leaf level by accounting for leaf surface properties, turbo- and thermophoretic components. Also, how to upscale these results to the canopy level from measurements that can now be acquired from remote sensing platforms (e.g. leaf area density) using multi-level and particle size-resolved canopy turbulence closure models will be explored. The model results will be evaluated at three forested sites using size-resolved mean particle concentration profiles and two-level eddy-covariance particle flux systems positioned above the canopy and in the understory.This project will provide improvements in process-level understanding of particle dry deposition and for mechanistic descriptions suitable for application in a range of numerical models from earth system models to regional scale air quality models. To facilitate maximal use of the research products derived, the data sets and the models will be made publically accessible via a project website. The project will support one post-doctoral scholar and one graduate student, who will have opportunity to engage with the broader scientific community via interaction with the BEACHON (Biosphere-atmosphere Exchange of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen) research team and European collaborators. Opportunities for undergraduate students will be offered within the BSES (Bachelor of Science in Environmental Science, http://www.indiana.edu/~bses/) program to undertake their capstone research experiences.

大气气溶胶颗粒浓度是了解历史和未来可能的气候强迫的最大不确定性之一，甚至区域大气化学模式也与现场观测的颗粒大小分布和组成显示出相当大的差异，部分原因是颗粒动力学的复杂性，包括干沉积。鉴于广阔的森林覆盖和相对较高的森林颗粒沉积速度，森林生态系统在去除气溶胶颗粒方面的作用正在引起许多科学学科和管理机构的越来越多的关注。然而，由于以下原因仍然存在重大的不确定性：(1)与实地测量粒径分辨通量和平均浓度相关的困难；(2)缺乏对冠层介质的详细和同时测量，更重要的是，缺乏对树叶表面特征的测量；(3)在描述冠层内部和正上方的运输剂（湍流）的所有主要特征方面存在挑战。本项目将采用实验和建模相结合的方法，在多个层次尺度（叶到冠层）上探讨颗粒沉积在森林表面的三个关键方面：(1)叶尺度上树叶收集机制的相对重要性和正确描述；(2)叶和非叶元素之间的沉积通量分配；(3)从[1]和[2]方面到整个生态系统的上尺度结果。将在具有“理想”微气象条件的不同森林地点（针叶林和阔叶林）和环境室内的受控实验中测量冠层尺度分辨率的颗粒通量和平均浓度剖面。这些实验的发现将通过考虑叶片表面特性、涡轮和热电泳成分，指导叶片水平上新的颗粒收集方案的发展。此外，如何将这些结果从现在可以从遥感平台（如叶面积密度）获得的测量结果中提升到冠层水平，使用多层次和粒径分辨冠层湍流闭合模型将被探索。模型结果将在三个森林站点进行评估，使用大小分辨的平均颗粒浓度剖面和位于冠层上方和林下的两级涡旋协方差颗粒通量系统。该项目将提高对颗粒干沉积过程水平的理解，并提供适合应用于从地球系统模型到区域尺度空气质量模型的一系列数值模型的机制描述。为了最大限度地利用所得的研究成果，数据集和模型将通过项目网站向公众提供。该项目将支持一名博士后学者和一名研究生，他们将有机会通过与BEACHON（生物圈-大气能量、气溶胶、碳、水、有机物和氮的交换）研究团队和欧洲合作者的互动，参与更广泛的科学界。本科生将有机会在BSES（环境科学学士学位，http://www.indiana.edu/~bses/）项目中进行他们的顶点研究经验。