CAREER: Quantifying the Effects of Liquid Water Content on the Spectral Albedo of Snow

职业：量化液态水含量对雪光谱反照率的影响

• 批准号: 2144243
• 负责人: Alden Adolph
• 金额: $ 55.72万
• 依托单位: Saint Olaf College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2027-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2144243&HistoricalAwards=false
• 关键词: CAREER; Quantifying; Effects; Liquid; Water

The highly reflective nature of snow means that it plays a critical role in the climate system; snow reflects solar energy and regulates global temperatures. Snow processes are especially relevant in the Arctic system, where temperatures are rising more rapidly than the global average, partially because of feedback processes that take place as snow melts. As air temperatures increase, snow begins to melt, which lowers the snow’s reflectivity and increases the amount of sunlight it absorbs. The absorbed light leads to further temperature increase, and this warming process can have far-reaching implications for our climate. Although snow is one of nature’s most reflective materials, the exact reflectivity can be quite variable. Several factors darken snow, such as larger snow grain sizes and impurities in the snow like dust, soot and algae. One factor that is not well understood is how the liquid water content in snow reduces reflectivity. This presents significant uncertainty in determining how changing snowpacks will impact the climate system, particularly in the Arctic, as wet snow becomes more prevalent due to more frequent rain on snow events and larger extent and duration of surface melt on ice sheets and glaciers. This project will enhance our understanding of wet snow reflectivity through field measurements in Minnesota and Colorado, lab experiments, and modeling. Our results will probe fundamental physical relationships and therefore, broadly apply to cold regions. As part of this work, undergraduate students will be engaged in the research projects. They will collect and analyze data in an Engineering Thermodynamics class and will design and build instrumentation for this work and to support other faculty projects in a new Engineering Fellows Program. The investigator will also share teaching materials about snow reflectivity and climate online and at a workshop for faculty at minority serving institutions.The naturally high albedo (or reflectivity) of snow provides a strong control on earth’s surface temperatures. Because of this critical role, accurately reproducing snow albedo is essential for effective climate modeling. Even in the Arctic, the already prevalent periods of wet snow are increasing because of more frequent rain on snow events and increased extent and duration of glacial surface melt; however, nearly all existing snow albedo models employ albedo schemes designed for dry snow. These models play a key role during snow melt because of the amplifying effects of the snow albedo feedback process, where melting snow leads to lower albedo, higher temperatures, and further snow melt. Therefore, explicitly incorporating the effects of liquid water content on snow albedo is a critical next step in improving model accuracy. The proposed work aims to quantify the effect of liquid water content on snow albedo, combining several approaches. 1) The investigator will conduct field-based measurements of albedo, liquid water content, grain size and snow impurities in Minnesota and at Niwot Ridge in Colorado to determine the effects of individual physical properties on the overall snow albedo. Wet snow conditions at these locations represent those that are increasingly common in the Arctic. 2) Through a new course-based undergraduate research experience (CURE) implemented in the Engineering Thermodynamics class, students will conduct laboratory measurements of the reflectance of artificial snow with controlled grain size and liquid water content. 3) The investigator will complement this work with two different modeling approaches to calculate wet snow albedo to investigate an array of snow conditions and inform potential changes to physically based snow albedo models. Studying these phenomena in different landscapes, in the laboratory, and in simulations will allow us to extrapolate our understanding of wet snow albedo to cold regions more broadly, particularly in the rapidly changing Arctic. This project will support the development of students through multiple avenues by providing opportunities to engage in research and build their scientific identities. The investigator will develop an Engineering Fellows Program in which students work with faculty over the course of the year on a design project, in addition to enrolling in a professional development seminar course. The investigator will also partner with the Ice Drilling Program Education team to serve as a visiting scientist in the School of Ice workshop and create an online Virtual Field Lab on snow albedo.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

雪的高反射性意味着它在气候系统中起着关键作用;雪反射太阳能并调节全球温度。降雪过程在北极系统中尤其重要，那里的气温上升速度超过全球平均水平，部分原因是雪融化时发生的反馈过程。随着气温的升高，雪开始融化，这降低了雪的反射率，增加了它吸收的阳光量。吸收的光导致温度进一步升高，这种变暖过程可能对我们的气候产生深远的影响。虽然雪是自然界最具反射性的材料之一，但确切的反射率可能会有很大的变化。有几个因素使雪变暗，例如较大的雪颗粒尺寸和雪中的杂质，如灰尘，烟灰和藻类。一个不太清楚的因素是雪中的液态水含量如何降低反射率。这在确定不断变化的积雪将如何影响气候系统方面存在很大的不确定性，特别是在北极，因为湿雪变得更加普遍，这是由于雪事件更频繁的降雨以及冰盖和冰川表面融化的范围和持续时间更大。这个项目将通过在明尼苏达州和科罗拉多州的实地测量、实验室实验和建模来增强我们对湿雪反射率的理解。我们的研究结果将探索基本的物理关系，因此，广泛适用于寒冷地区。作为这项工作的一部分，本科生将从事研究项目。他们将收集和分析工程热力学类的数据，并将设计和建造这项工作的仪器，并支持在一个新的工程研究员计划的其他教师项目。研究人员还将在网上和为少数民族服务机构的教师举办的研讨会上分享有关雪反射率和气候的教学材料。雪的自然高反射率（或反射率）对地球表面温度提供了强有力的控制。由于这一关键作用，准确地再现雪覆盖对于有效的气候建模至关重要。即使在北极地区，由于更频繁的降雪事件和冰川表面融化的范围和持续时间增加，已经普遍存在的湿雪期正在增加;然而，几乎所有现有的雪雪融化模型都采用了为干雪设计的雪融化方案。这些模型在雪融化过程中起着关键作用，因为雪的温度反馈过程的放大效应，融化的雪导致温度降低，温度升高，雪进一步融化。因此，明确纳入液态水含量对雪的影响是提高模型精度的关键下一步。拟议的工作旨在量化液态水含量对雪的影响，结合几种方法。1)调查人员将在明尼苏达州和科罗拉多的尼沃特岭对雪的含水量、液态水含量、粒度和雪杂质进行实地测量，以确定个别物理性质对整体雪含水量的影响。这些地点的湿雪条件代表了北极地区日益普遍的情况。2)通过一个新的基于课程的本科研究经验（CURE）在工程热力学类实施，学生将进行人工雪的反射率与控制粒度和液态水含量的实验室测量。3)研究人员将通过两种不同的建模方法来补充这项工作，以计算湿雪雪量，以调查一系列雪况，并告知基于物理的雪量模型的潜在变化。在不同的景观中，在实验室和模拟中研究这些现象将使我们能够将我们对湿雪的理解更广泛地推广到寒冷地区，特别是在快速变化的北极地区。该项目将通过多种途径支持学生的发展，提供参与研究和建立科学身份的机会。调查员将开发一个工程研究员计划，学生在一年的设计项目过程中与教师合作，除了参加专业发展研讨会课程。该研究员还将与冰钻项目教育团队合作，担任冰学院研讨会的访问科学家，并创建一个关于雪岩的在线虚拟现场实验室。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。