Cloud Droplet Evolution and Thermal Radiation

大气中的水在地球所有三个阶段的辐射收支中都起着至关重要的作用。水蒸气是地球的主要温室气体；云在地球的辐射能量平衡中发挥着重要作用。然而，在理解水在大气中的辐射作用方面仍然存在很大的不确定性。这种不确定性在云与辐射的相互作用中表现得尤为突出。一些研究人员提出，有关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水分增加的影响和缺失的云辐射物理碎片的影响是该项目的主要动机。该项目的目标是更好地理解热辐射在暖云滴演化中的作用：稳定性、蒸发和凝结增长。实验室测量的重点将是辐射增强的云滴凝结生长和蒸发。计划有两个独立的、互补的实验室设备：一个是具有辐射冷却/冷凝的稳定、等压流动过程，另一个是具有绝热膨胀冷却和辐射加热/蒸发的非稳定间歇过程。将对液滴的辐射特性和辐射增强的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的云模拟的数学模型。测量和建模都将用于验证和更好地理解热辐射在云滴演化中的作用。智力优势：这项研究在从基础、科学导向到产品导向的层面上具有智力优势。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中的基本问题：不确定的云反照率，不确定的气溶胶性质，“异常”的短波辐射吸收，异常的长波发射，水蒸气连续吸收和发射，以及在不断变化的辐射和热力学环境中的云滴稳定性问题。如果这个项目能够利用相变辐射引起的凝聚红外发射的光谱变化来更早、更可靠地感知毛毛雨的开始，那么遥感产品和数据检索将受到影响。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，这项研究将最直接地影响一名立志成为教授的博士生的教育和职业生涯，作为他研究生培训的一部分，他想回到他的HBCU硕士学位机构，并就研究成果和在研究生院的经验发表演讲。在当地，将为K-12年级的学生举办关于水性质、相变热传递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。这项研究还将作为设计项目纳入伊利诺伊大学的研究生课程，从而产生更广泛的教育影响。在更大的社会层面上，这项研究也将产生深远的影响。本文所获得的辐射相变发现将有助于更好地从根本上理解云的微物理，并可能为改进全球气候理解和数值天气预报打开一扇大门。通过探索“反常”红外线水辐射、水蒸气连续体和蒸汽凝结相变之间的联系，这项研究在改变大气辐射模型的方式方面具有潜在的变革作用。该项目的最终广泛影响将是一个更有见识的社会，更准确地了解地球主要热调节流体和主要温室物质：水的基本热物理性质。

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.