MRI: Development of a Water Vapor and Temperature Mapping System to Study Cloud-turbulence Interactions in the Michigan Technological University (MTU) Pi-Chamber

气溶胶和云是调节地球辐射平衡和气候的最重要因素之一，它们以复杂的方式相互作用。气溶胶起着云核的作用，决定着云的形成和生命周期；相反，云会改变并带走大气中的气溶胶。湍流通过影响云滴大小分布、气溶胶成核、水化和活化以及空间分离在这些过程中起着关键作用。例如，干燥空气被夹带到云边缘的饱和空气中进行混合是一个重要的过程，但仍未完全理解，需要进一步的实验室和实地研究。由于湍流引起的小空间（100mm）和时间（10s）尺度的水汽和温度波动，理解和模拟气溶胶与云之间复杂的相互作用具有挑战性。需要开发新的分析工具，将这些精细结构过程与气候相关的云特性联系起来。新仪器的研究将有助于理解气溶胶、云和湍流之间错综复杂的相互作用，因此将产生明确而关键的更广泛的影响，而不仅仅是单纯的科学好奇心。该项目还将通过实践研究和指导活动促进研究生和本科生的职业发展，并为培养新一代乐器演奏家做出贡献。为了帮助填补STEM领域的性别和少数族裔差距，该项目将与密歇根理工大学（MTU）的机构公平和包容办公室合作，并通过密歇根学院/大学合作计划，增加对代表性不足群体学生的接触。这个发展项目的科学目标是在密歇根理工大学的湍流多相云室中设计、建造和测试一种新的仪器，用于研究湍流对云和气溶胶的影响。该仪器将大大提高实验室的能力，并使新的令人兴奋的研究成为可能。该室内是一个社区共享的设施，可以产生可控的环境和对流湍流条件，并通过不同的模式（例如，通过膨胀或通过垂直温度梯度混合）形成云（暖、冷或混合）。在混合模式下，云可以维持数小时或数天，因此可以在没有时间限制的情况下详细研究微物理特性和气溶胶-云湍流相互作用。为了理解湍流如何影响温度、水蒸气和液态水场，我们需要绘制出它们的时空分布。为了实现这一目标，该项目将开发一种分析工具，在不影响湍流条件的情况下，对腔室内的温度和水（蒸汽和液体）分布进行成像，同时提供与感兴趣的过程相关的空间和时间分辨率（~1-20厘米和~1秒）。远程成像系统基于拉曼散射，它携带着水浓度和温度的信息。该仪器将成为云室共享设施的组成部分，增强其科学和分析能力，扩大国家和国际合作。新仪器的研究将包括：a)均匀与非均匀混合对云滴生长和尺寸分布的影响，相关的长度尺度以及湍流如何影响饱和比场。b)饱和比场的小尺度细节，它如何决定初始激活、云液滴生长和尺寸分布演变，以及饱和比波动引起的液滴演变如何反馈到云湍流中。c)厘米尺度间歇对气溶胶空间分离、加湿、活化和液滴形成的影响。

Aerosols and clouds are among the most important factors regulating our planet's radiative balance and climate, while interacting in complex manners. Aerosols act as cloud nuclei, determining the formation and lifecycle of clouds; conversely, clouds transform and remove aerosols from the atmosphere.Turbulence plays a key role in these processes by influencing cloud droplet size distribution, aerosol nucleation, hydration and activation, and spatial segregation. For example, mixing by entrainment of dry air into saturated air at the edges of a cloud is an important and still not fully understood process that requires further laboratory and field studies. Understanding and modeling the complex interactions between aerosols and clouds is challenging due to turbulence-induced water vapor and temperature fluctuations at small spatial (100mm) and temporal (10s) scales. Novel analytical tools need to be developed to link these fine-structure processes to climate-relevant cloud properties.The research enabled by the new instrument will help understanding the intricacies of the interactions between aerosol, clouds and turbulence, and will thus have clear and critical broader impacts, beyond simple scientific curiosity. The project will also promote graduate and undergraduate students' career development through hands-on research and mentoring activities and contribute to growing the new generation of instrumentalists. To help filling gender and minorities gaps in STEM, the project will work with the office of institutional equity and inclusion at Michigan Technological University (MTU) and through the Michigan College/University Partnership Program to increase the outreach to students from under-represented groups.The scientific objective of this development project is to design, construct and test a new instrument for the study of the effects of turbulence on clouds and aerosols in the Michigan Technological University's turbulent multiphase cloud chamber. This instrument would significantly enhance the capability of the chamber and enable new exciting research. The chamber - a community shared facility - can generate controlled environmental and convective turbulent conditions, and form clouds (warm, cold or mixed) through different modes (e.g., by expansion or by mixing through a vertical temperature gradient). In the mixing mode, clouds can be maintained for several hours/days and therefore microphysical properties and aerosol-cloud-turbulence interactions can be studied in detail with no time constraints. To understand how turbulence shapes temperature, water vapor and liquid water fields, one needs to map their spatial and temporal distributions. To achieve this goal, the project will develop an analytical tool for imaging temperature and water (vapor and liquid) distributions inside the chamber without affecting the turbulent conditions, while providing spatial and temporal resolutions relevant to the processes of interest (~1-20 cm and ~1 s).The remote imaging system is based on Raman scattering that carries information on water concentrations and temperature. The instrument will become integral part of the cloud chamber shared facility enhancing it scientific and analytical capacity and expanding national and international collaborations. Research enabled by the new instrument will include: a) Study of the effect of homogeneous vs. inhomogeneous mixing on cloud droplet growth and size distribution, the relevant length scales and how turbulence influence the saturation ratio field. b) Small-scale details of the saturation ratio field, how it determines initial activation, cloud droplet growth and size distribution evolution, and how the droplet evolution caused by the saturation ratio fluctuations feedback into the cloud turbulence. c) Effect of centimeter-scale intermittencies on aerosol spatial segregation, humidification, activation and droplet formation.