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: 1102227
• 负责人: Gabriel Katul
• 金额: $ 20.1万
• 依托单位: Duke 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 2015-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1102227&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型也与颗粒尺寸分布和成分的现场观测结果存在相当大的差异，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率和森林上空相对较高的颗粒沉积速度，森林生态系统在去除气溶胶颗粒方面的作用越来越受到许多科学学科和监管机构的关注。然而，由于以下原因仍然存在显着的不确定性：(1) 与颗粒尺寸解析通量和平均浓度的现场测量相关的困难，(2) 缺乏对冠层介质的详细和同步测量，更重要的是，缺乏对叶子表面特征的测量，以及(3 ）描述树冠内部和树冠上方输送介质（湍流）的所有主要特征的挑战。该项目将通过探索：（1）树叶收集的相对重要性和正确描述，在多个层次尺度（叶子到树冠）上使用组合实验和建模方法来解决森林表面颗粒沉积的三个关键方面叶尺度的机制，(2) 叶面和非叶面元素之间的沉积通量分配，以及 (3) 从方面 [1] 和 [2] 到整个生态系统的放大结果。冠层尺度尺寸解析的颗粒通量平均浓度分布将在具有“理想”微气象条件的各种森林地点（针叶树和阔叶树）以及环境室的受控实验中进行测量。这些实验的结果将通过考虑叶片表面特性、涡轮和热泳组件来指导在叶片水平上开发新的颗粒收集方案。此外，还将探讨如何使用多级和颗粒尺寸解析的冠层湍流闭合模型，将这些结果从现在可以从遥感平台（例如叶面积密度）获取的测量结果升级到冠层水平。该模型结果将在三个森林地点使用尺寸分辨的平均颗粒浓度分布和位于树冠上方和林下的两级涡流协方差颗粒通量系统进行评估。该项目将改进对颗粒干燥的过程级理解沉积和机械描述适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。为了最大限度地利用所得出的研究产品，数据集和模型将通过项目网站公开访问。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-大气交换能量、气溶胶、碳、水、有机物和氮）研究团队的互动，与更广泛的科学界接触和欧洲合作者。 BSES（环境科学理学学士，http://www.indiana.edu/~bses/）计划将为本科生提供获得顶峰研究经验的机会。