POWRE: Characterization of Phase Transformations in Stratospheric Aerosols

这一POWRE项目将涉及调查与极地平流层云有关的成分的大气气溶胶的基本物理、光学和热力学性质。这项研究的具体目标是：(1)根据大气层实地观测制作模型气溶胶；(2)发展控制粒子环境(温度和气相成分)的能力；(3)发展产生过饱和气相成分以模拟云室条件的能力；(4)确定平流层下层和对流层上层悬浮单粒子气溶胶的相转变条件；(5)制作关于压力、温度和成分领域的平衡和非平衡相转变的多组分相图。将设计和建造一种新的低温单粒子装置。这个粒子悬浮室将能够重现类似于对流层上层和平流层下层普遍存在的温度、冷却速度和气相组成。此外，经过一定的修改，该装置将作为单一的固体粒子云室。对于大气气溶胶的表征，将使用粒子质量和Mie散射来确定光学和热力学性质，而拉曼光谱将用于确定化学成分和物理相。这项调查的结果将确定实际的气溶胶成分、物理相，以及在极地平流层可见的条件下可能发生的变化。这项POWRE奖将允许PI与布鲁克海文国家实验室的科学家密切合作，新仪器将设在那里。PI将获得更多的大气化学研究经验，她的学生将有机会参与最先进的科学。

This POWRE project will involve the investigation of the fundamental physical, optical and thermodynamic properties of atmospheric aerosols with compositions relevant to polar stratospheric clouds. The specific objectives for this research are: (1) to produce model aerosols based on atmospheric field observations, (2) to develop the ability to control a particle's environment (temperature and gas phase composition), (3) to develop the capability to produce supersaturated gas phase compositions to simulate cloud chamber conditions, (4) to define the phase transformation conditions for suspended, single particle aerosols of lower stratosphere and upper troposphere importance, (5) to produce multi-component phase diagrams for equilibrium and non-equilibrium phase transitions in pressure, temperature and composition domains. A new low-temperature single particle apparatus will be designed and constructed. This particle levitation chamber will be capable of reproducing temperatures, cooling rates, and gas phase compositions similar to those prevalent in the upper troposphere and lower stratosphere. In addition, with certain modifications, this apparatus will serve as a single solid-particle cloud chamber. For the characterization of atmospheric aerosols, particle mass and Mie scattering will be used to determine the optical and thermodynamic properties, while Raman spectroscopy will be employed for determining the chemical composition and physical phase. The results from this investigation will define the actual aerosol composition, physical phases, and the transformations that can occur under conditions seen in the polar stratosphere. This POWRE award will allow the PI to work closely with scientists at Brookhaven National Laboratory, where the new apparatus will be located. The PI will gain additional research experience in atmospheric chemistry, and her students will have the opportunity to get involved in state-of-the-art science.