Collaborative Research: Inferring Marine Particle Properties from Polarized Volume Scattering Functions

合作研究：从偏振体散射函数推断海洋颗粒特性

• 批准号: 1459180
• 负责人: Ping Yang
• 金额: $ 19.71万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459180&HistoricalAwards=false
• 关键词: Collaborative; Research; Inferring; Marine; Particle

Understanding biogeochemical cycles and their interaction with the climate system requires quantifying the various forms of materials in the global ocean. In particular, the chemical composition and size distribution of living and non-living particles in the ocean have an enormous impact on marine ecosystems, including the dynamics of marine food chains, the vertical transmission of solar energy, and the transport of organic matter and trace elements. These particle characteristics not only affect but reflect changes in many biogeochemical processes in the ocean. In this project, a team of scientists will launch a set of technical and numerical modeling innovations that will allow them to determine key biogeochemical quantities from optical observations of the angular distribution of scattered light. The project will involve an interdisciplinary team of experts, who will theoretically model the optics of marine particles, develop an innovative advanced mathematical modeling scheme, and then laboratory- and field-test and validate the approach for observing marine particle properties. When perfected, the technique should see a broader application, as it will be designed to be amenable to operation on ship-borne and autonomous platforms with the potential to provide estimates of the particle size distribution and composition at high temporal and spatial resolutions. It should thus benefit different fields requiring detailed knowledge of aquatic particles (biogeochemistry, biology, optics). The project will also provide for the training and support of graduate and undergraduate students as well as public educational outreach, including a special effort to reach Native Americans in North Dakota.The goal of this project is to derive water-column quantitative particle size and composition information from in situ unobtrusive volume scattering function (VSF) measurements to characterize marine biogeochemical particulate stocks. The angular patterns of the scattered intensity and polarization state of the scattered light by particles can be described in terms of a 4x4 Mueller matrix (S) that is intrinsically determined by the sizes, shapes, composition, and structures of the particles. The particle properties can be, therefore, potentially inferred from measurements of S. Unfortunately, the complete Mueller matrix of oceanic waters has been seldom measured. Even the most commonly measured component, the volume scattering function (element S11) representing the angular distribution of unpolarized light, was scarcely measured until recently, followed by development of an inversion technique to derive size distributions and composition of particles from the VSF. Recently, a commercial product, LISST-VSF, became available for measuring the Mueller matrix components S11 (VSF), S12 (linear polarization), and S22 (cross-polarization), potentially providing an avenue to obtain a much more detailed characterization of particles. This project will incorporate the additional information provided by S12 and S22 using recent advances in scattering modeling to further constrain the inversion with the following: (i) better knowledge in particle shapes using S22 (spherical vs. non-spherical); (ii) reduced uncertainty using both S11 and S12; and (iii) further improved capability to characterize particles in the size range of 0.02 to 200 um. The study should greatly enhance our ability to quantify size distributions and refractive indices (closely linked to particle densities) for particle groups such as phytoplankton cells, detrital particles, organic particles, mineral particles, bubbles, and emulsified oil (if present).

了解生物地球化学周期及其与气候系统的相互作用需要量化全球海洋中各种形式的材料。 特别是，海洋中生物和非生物颗粒的化学组成和尺寸分布对海洋生态系统有巨大影响，包括海洋食品链的动力学，太阳能的垂直传播以及有机物和微量元素的运输。 这些粒子特征不仅影响，而且反映了海洋许多生物地球化学过程的变化。 在这个项目中，一组科学家将发起一系列技术和数值建模创新，使他们能够从散射光的角度分布的光学观察中确定关键的生物地球化学数量。 该项目将涉及一个跨学科的专家团队，从理论上讲，他们将对海洋颗粒的光学进行建模，开发一种创新的高级数学建模方案，然后进行实验室和现场测试，并验证观察海洋颗粒特性的方法。完善后，该技术应看到更广泛的应用，因为它将设计为在船舶传播和自主平台上的操作，并有可能估算高时间和空间分辨率的粒径分布和组成。 因此，它应该受益于需要详细了解水生颗粒（生物地球化学，生物学，光学）的不同领域。 该项目还将提供对毕业生和本科生的培训和支持，以及公共教育外展活动，包括特殊的努力，以吸引北达科他州的美洲原住民。该项目的目的是从原位的量化粒度和构成粒径和构成信息中得出原位不可动摇的数量散射功能（VSF）的测量，以表征海洋生物群的特征。 可以用颗粒散射光的散射强度和极化状态的角模式可以用4x4 mueller矩阵来描述，该矩阵由粒子的尺寸，形状，组成和结构本质上确定。因此，可以从S.的测量中推断出粒子的特性，不幸的是，很少测量过海洋水域的完整穆勒矩阵。即使是最常见的成分，也几乎无法测量代表非偏光光的角度分布的体积散射函数（元素S11），直到最近才能开发出反转技术以从VSF中得出尺寸分布和粒子的组成。 最近，一种商业产品Lisst-VSF可用于测量Mueller矩阵组件S11（VSF），S12（线性极化）和S22（交叉极化），有可能提供途径以获得更详细的颗粒表征。 该项目将使用散射建模方面的最新进展来结合S12和S22提供的其他信息，以进一步限制以下情况：（i）使用S22（球形与非球形）更好地了解粒子形状的知识； （ii）使用S11和S12降低了不确定性； （iii）进一步提高了在0.02至200 um尺寸范围内表征颗粒的能力。这项研究应大大提高我们量化尺寸分布和折射率（与颗粒密度密切相关的颗粒群）的能力，例如浮游植物细胞，碎屑颗粒，有机颗粒，有机颗粒，矿物颗粒，气泡和乳化油（如果存在）。