Cloud Droplet Evolution and Thermal Radiation

云滴演化和热辐射

• 批准号: 1457128
• 负责人: M Q Brewster
• 金额: $ 36.83万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1457128&HistoricalAwards=false
• 关键词: Cloud; Droplet; Evolution; Thermal; Radiation

Water in the atmosphere plays a crucial role in Earth's radiation budget in all three phases. Water vapor is Earth's primary greenhouse gas; clouds play a major role in Earth's radiative energy balance. Yet there remain significant uncertainties in the understanding of water's radiative roles in the atmosphere. This uncertainty shows up prominently in cloud-radiation interactions. Some researchers have suggested there are significant missing pieces of fundamental physics regarding clouds and thermal radiation. The need to understand better the effect of increasing amounts of water in the atmosphere and the implications of missing pieces of cloud-radiation physics are the primary motivations for this project.The objective of this project is to establish a better understanding of the role of thermal radiation in warm cloud droplet evolution: stability, evaporation, and condensation growth. Lab measurements will focus on radiation-augmented cloud droplet condensation growth and evaporation. Two separate, complementary laboratory devices are planned: a steady, isobaric flow process with radiative cooling/condensation and an unsteady, batch process with adiabatic expansion cooling followed by radiative heating/evaporation. Theoretical development and validation will be done for both droplet radiative properties and radiation-augmented mass transfer to obtain mathematical models for interpreting lab data and for microphysical and larger scale cloud simulations. Both measurements and modeling will be used to provide validation for and better understanding of the role of thermal radiation in cloud droplet evolution.Intellectual Merit: This study has intellectual merits at levels ranging from fundamental, scientifically oriented to product oriented. New knowledge will be generated about radiative- and phase-transitions for the most important thermal regulating substance on the planet. The findings will impact fundamental questions in cloud physics and atmospheric radiation: uncertain cloud albedos, uncertain aerosol properties, "anomalous" shortwave radiation absorption, anomalous longwave emission, water-vapor continuum absorption and emission, and the problem of cloud droplet stability in radiative and thermodynamic environments that are constantly changing. Remote sensing products and data retrieval will be impacted if this project can exploit spectral changes in condensing IR emission induced by phase-transition radiation to sense the onset of drizzle earlier and more reliably.Broader Impacts: This study will also have broader impacts, ranging from individuals to society at-large.At the individual level this study will most immediately affect the education and career of a PhD graduate student whose aspirations are to become a professor and as part of his graduate training wants to return to his HBCU masters-degree institution and make presentations on research findings and experience in graduate school. Locally, workshops will be conducted for K-12 students on water properties, phase-change heat transfer, and global climate change in which inexpensive atmospheric radiation and cloud-formation monitors will be built and tested. This study will also have a broader educational impact by being incorporated into the graduate curriculum at the University of Illinois as a design project.At a larger, societal level this study will also have far-reaching impact. The radiative phase-transition findings obtained herein will allow a better fundamental understanding of cloud microphysics and may open a door to improved global climate understanding as well as numerical weather prediction. By exploring the connections between "anomalous" infrared water radiation, the water-vapor continuum, and vapor-condensed phase transition, this study is potentially transformative in changing the way atmospheric radiation is modeled. The ultimate broad impact of this project will be a more informed society with a more accurate understanding of the fundamental thermophysical properties of Earth's primary thermal regulating fluid and principal greenhouse substance: water.

在这三个阶段中，大气中的水对地球的辐射收支起着至关重要的作用。水蒸气是地球上主要的温室气体；云在地球的辐射能量平衡中起着重要作用。然而，在对水在大气中的辐射作用的理解上仍有很大的不确定性。这种不确定性在云-辐射相互作用中表现得尤为突出。一些研究人员认为，关于云和热辐射的基础物理学存在重大缺失。需要更好地了解大气中不断增加的水的影响以及云辐射物理学缺失部分的含义是这个项目的主要动机。该项目的目标是更好地了解热辐射在暖云液滴演化中的作用：稳定性、蒸发和凝结生长。实验室测量将集中在辐射增强的云滴凝结生长和蒸发。两个独立的，互补的实验室装置计划：一个稳定的，等压流过程，辐射冷却/冷凝和一个非稳定的，间歇式过程，绝热膨胀冷却，然后辐射加热/蒸发。将对液滴辐射特性和辐射增强传质进行理论开发和验证，以获得用于解释实验室数据以及微物理和更大规模云模拟的数学模型。测量和模拟都将用于验证和更好地理解热辐射在云滴演化中的作用。智力价值：本研究具有智力价值，从基础，科学导向到产品导向。将产生关于地球上最重要的热调节物质的辐射和相变的新知识。这些发现将影响云物理和大气辐射的基本问题：不确定的云反照率，不确定的气溶胶特性，“异常”短波辐射吸收，异常长波发射，水蒸气连续体吸收和发射，以及云滴在不断变化的辐射和热力学环境中的稳定性问题。如果该项目能够利用相变辐射引起的压缩红外发射光谱变化，更早、更可靠地感知毛毛雨的发生，将对遥感产品和数据检索产生影响。更广泛的影响：这项研究也将产生更广泛的影响，从个人到整个社会。在个人层面上，这项研究将最直接地影响到一个博士研究生的教育和职业生涯，他的愿望是成为一名教授，作为他研究生培训的一部分，他希望回到他的HBCU硕士学位机构，并在研究生院发表研究成果和经验。在当地，将为K-12学生举办关于水性质、相变传热和全球气候变化的讲习班，其中将建造和测试廉价的大气辐射和云形成监测仪。本研究也将有更广泛的教育影响，被纳入伊利诺伊大学的研究生课程作为一个设计项目。在更大的社会层面上，这项研究也将产生深远的影响。本文获得的辐射相变结果将有助于更好地理解云微物理，并可能为改进全球气候理解和数值天气预报打开一扇门。通过探索“异常”红外水辐射、水蒸气连续体和蒸汽凝聚相变之间的联系，这项研究可能会改变大气辐射的建模方式。这个项目的最终广泛影响将是一个更有见识的社会，对地球主要的热调节流体和主要的温室物质——水的基本热物理性质有更准确的理解。