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Radiative Cooling and Homogeneous Droplet Freezing in Laboratory Clouds

实验室云中的辐射冷却和均匀液滴冻结

基本信息

批准号：
2152233
负责人：
M Q Brewster
金额：
$ 41.71万
依托单位：
University of Illinois at Urbana-Champaign
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：
2022-03-01 至 2025-02-28
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2152233&HistoricalAwards=false
关键词：
Radiative Cooling Homogeneous Droplet Freezing

项目摘要

The current global imbalance between incoming solar radiation and outgoing infrared radiation continues to warm our planet. The amount of water in the warming atmosphere also continues to increase. Phase changes of water—evaporation, condensation, and freezing—are the important processes that drive tornadoes, super-cell thunderstorms, hurricanes and other severe weather; but our understanding about these phase-change processes and their interactions with radiation is still insufficient at present. To increase our understanding of these phase changes of water and improve severe weather forecast and long-term climate change prediction, laboratory and analytical/theoretical study will be carried out in this study. This project will help to train a female PhD graduate student who received her master’s degree at an HBCU institution. Local workshops will be conducted for K-12 students on water properties, phase-change heat transfer, and global climate change.In this research, radiatively induced cloud-droplet growth, cooling, and freezing will be studied both experimentally in laboratory-produced clouds and computationally with analytical and theoretical modeling. Laboratory experiments will be conducted in which cloud droplets will be exposed to radiative cooling, similar to what can happen in cloud-top generating cells in extra-tropical, cold-season cyclones or other storm systems. Cooling will be such as to induce homogeneous freezing of droplets. Changes in droplet size due to mass transfer (primarily growth via condensation) will be measured as well as temperature changes. An analytical model of the radiative cooling and condensation process will be developed. The common modeling assumptions of homogeneous (droplet-non-specific) supersaturation and droplet-non-specific radiation, which have recently been questioned, will be investigated and improved upon. Laboratory measurements will be used to develop and validate new modeling assumptions by comparing the measurements with analytical predictions. New theory will be developed for the effect of droplet-specific, non-homogeneous supersaturation. New basic scientific information about the state of homogeneously frozen droplets with solute will also be obtained. These results will impact a fundamental problem in cloud microphysics: the problem of numerically modeling cloud droplet evolution in a complex, constantly changing fluid dynamic, thermodynamic, and radiative atmospheric environment. The results of this study could lead to a new and deeper understanding of basic processes that will not only benefit the environment and climate but other areas of engineering and technology such as phase-change heat exchanger design and electronics cooling. The ultimate broad impact of this study is a better scientific basis for understanding cloud microphysics and for conducting weather prediction and global circulation and climate modeling.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.

目前全球太阳辐射和红外辐射之间的不平衡继续使我们的星球变暖。大气中的水含量也在不断增加。水的蒸发、凝结、冻结等相变是驱动龙卷风、超级单体雷暴、飓风等灾害性天气的重要过程，但目前对这些相变过程及其与辐射的相互作用的认识还很不足。为了提高我们对水的这些相变的理解，改善恶劣天气预报和长期气候变化预测，本研究将进行实验室和分析/理论研究。该项目将帮助培训一名在HBCU机构获得硕士学位的女博士研究生。当地的研讨会将进行K-12的学生在水的属性，相变传热，和全球气候变化。在这项研究中，辐射诱导云滴的增长，冷却和冻结将在实验室产生的云和计算分析和理论模型进行研究。将进行实验室实验，其中云滴将暴露于辐射冷却，类似于热带以外的冷季气旋或其他风暴系统中云顶生成细胞中可能发生的情况。冷却将导致液滴的均匀冻结。将测量由于质量转移（主要是通过冷凝生长）引起的液滴尺寸变化以及温度变化。将建立辐射冷却和凝结过程的分析模型。均匀（液滴非特异性）过饱和和液滴非特异性辐射，最近受到质疑的共同建模假设，将进行调查和改进。实验室测量结果将用于通过将测量结果与分析预测进行比较来开发和验证新的建模假设。将为液滴特定的、非均匀过饱和的影响发展新的理论。还将获得关于具有溶质的均匀冷冻液滴状态的新的基本科学信息。这些结果将影响云微物理学中的一个基本问题：在复杂的、不断变化的流体动力学、热力学和辐射大气环境中数值模拟云滴演变的问题。这项研究的结果可能会导致对基本过程的新的和更深入的理解，这不仅有利于环境和气候，而且有利于工程和技术的其他领域，如相变热交换器设计和电子冷却。这项研究的最终广泛影响是为理解云微物理学和进行天气预报以及全球环流和气候建模提供了更好的科学基础。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。