Collaborative Research: Hygroscopic Properties of Aerosol Organics

气溶胶通过吸收和散射光直接促进地球的辐射平衡，通过使云滴成核而增加行星反照率间接促进地球的辐射平衡。这两种效应都依赖于吸湿性生长，但有机物对气溶胶吸湿性的贡献尚不清楚，这限制了模拟这些效应的努力。本研究将通过现场测量、实验室实验和建模来解决有关气溶胶吸湿性的几个重要问题：(1)在亚饱和和过饱和条件下，水溶性有机碳（WSOC）对吸湿性生长的贡献是什么？(2) WSOC的化学和物理性质是什么？(3) Köhler理论和热力学平衡模型在多大程度上解释了观察到的无机和有机混合气溶胶的水显微镜生长和云凝结核（CCN）活性？为了回答这些问题，夏季将在沙漠研究所的高海拔风暴峰实验室（SPL）收集气溶胶样本。样品的详细无机和有机组成将用最先进的分析技术进行测量，以确定迄今为止尚未形成的高分子量WSOC。样品的水提取物和分离的WSOC将被重新雾化，以直接测量它们对吸湿生长和CCN活性的贡献。测量的生长因子和CCN活性将使用Köhler理论和基于结构的热力学活性模型进行调和。这项工作的结果将提高模拟无机和有机混合气溶胶吸湿生长的能力。本项目生产的高分子量WSOC化合物的明确处理将被纳入E-AIM热力学平衡模型的在线版本，供全世界的研究人员和学生使用。最终，该项目的结果将提供可纳入大尺度气候模型的信息，以更好地预测直接和间接的气溶胶辐射效应，如水溶性有机物的吸湿性生长曲线和不同无机和有机成分气溶胶的Köhler理论参数化。该研究将作为风暴峰地球科学研究（GRASP）活动的一部分纳入学生项目，该活动吸引了来自代表性不足群体的学生。在2010年冬季，SPL还将为几所大学举办大气科学实地课程。该项目将允许参加这些课程的学生在实地部署期间与项目研究人员一起工作。参与研究小组的研究生本科生参与实验室实验、数据分析和结果发表。

Aerosols contribute to the Earth's radiation balance directly by absorbing and scattering light and indirectly by nucleating cloud droplets which increase planetary albedo. Both effects depend on hygroscopic growth, but the contribution of organics to aerosol hygroscopicity is not well understood--limiting efforts to model those effects. This study will address several important questions regarding aerosol hygroscopicity through field measurements, laboratory experiments, and modeling: (1) What is the contribution of water-soluble organic carbon (WSOC) to hygroscopic growth under sub- and super-saturated conditions?; (2) What are the chemical and physical properties of WSOC?; and (3) How well can Köhler theory and thermodynamic equilibrium modeling account for observed hydroscopic growth and cloud condensation nucleus (CCN) activity of mixed inorganic and organic aerosols? To answer these questions, aerosol samples will be collected at the Desert Research Institute's high-elevation Storm Peak Laboratory (SPL) during summer. Detailed inorganic and organic composition of the samples will be measured with state-of-the-art analytical techniques to identify heretofore unspeciated high molecular weight WSOC. Water extracts of the samples and isolated WSOC will be re-aerosolized to directly measure their contribution to hygroscopic growth and CCN activity. Measured growth factors and CCN activity will be reconciled using Köhler theory and structure-based thermodynamic activity models. The results of this work will improve ability to simulate hygroscopic growth for aerosols of mixed inorganic and organic composition. The explicit treatment of high molecular weight WSOC compounds produced in this project will be incorporated into the on-line version of the E-AIM thermodynamic equilibrium model for use by researchers and students worldwide. Ultimately, the project's results will provide information that can be incorporated into large-scale climate models to better predict direct and indirect aerosol radiative effects, such as hygroscopic-growth curves for water soluble organics and parameterizations of Köhler theory for aerosols of different inorganic and organic composition. The research will be incorporated into student projects as part of the Geoscience Research at Storm Peak (GRASP) activity, which engages students from underrepresented groups. During the winter of 2010, SPL will also host atmospheric science field courses for several universities. The project will allow the students taking these courses to work together with project researchers during the field deployment. Graduate undergraduate students from the involved research groups participate in laboratory experiments, data analysis, and publication of the results.