Individual-particle Aerosol Experiments in the Marine Troposphere

海洋边界层和自由对流层中的气溶胶粒子既直接通过辐射后向散射影响全球太阳辐射平衡，也间接作为云凝结核影响太阳辐射平衡。这个项目将使用单个粒子的方法来检查影响气溶胶粒子尺寸分布、浓度和化学成分的对流层过程。主要重点将放在南太平洋偏远地区的海洋边界层和覆盖该层的层积云上。分析将使用自动电子束仪器，特别是新的扫描电子显微镜。该研究小组在过去十年中开发的方法允许通过定量测定组成和形态来研究大量颗粒。这项研究的数据将用于处理大气气溶胶研究中目前存在的问题，包括：(A)海洋气溶胶粒子的产生、分级和反应；(B)天然非海盐硫酸盐粒子的产生；(C)海洋平流层积云中气溶胶粒子在水滴和间隙空气之间的分配；(D)气溶胶粒子的云处理；(E)气溶胶在海洋对流层中的远距离输送过程中的演变。作为一项辅助任务，将使用高空间分辨率的透射电子显微镜，通过成像和化学分析来研究超微到亚微米复杂粒子的结构和组成。透射电子显微镜还可以检查亚微米级单个颗粒中涉及硝酸盐和氨的反应。拟议的研究综合起来，将提供有关海洋对流层中出现的各种粒子类型的精细数据，这些粒子类型会影响辐射后向散射和云的微物理特性。

Aerosol particles in the marine boundary layer and free troposphere impact the global solar radiation balance, both directly through radiation backscatter and indirectly as cloud condensation nuclei. This project will use individual-particle methods to examine tropospheric processes that affect aerosol- particle size distribution, concentrations, and chemical compositions. Primary focus will be on the marine boundary layer and stratocumulus clouds that cap that layer in the remote areas of the South Pacific. Analyses will be performed with automated electron-beam instruments, especially the new scanning electron microscope. Methods developed by this research group over the past decade allow the study of large numbers of particles by quantitative determination of composition and morphology. The data from this research will be used to address current issues in atmospheric aerosol research, including (a) the generation, fractionation, and reaction of marine aerosol particles; (b) production of natural, non-sea-salt sulfate particles; (c) partitioning of aerosol particles between droplets and interstitial air in marine stratocumulus clouds; (d) cloud processing of aerosol particles; and (e) evolution of aerosols during long-range transport in the marine troposphere. As a ancillary task, the structure and composition of complex supermicron to submicron particles will be investigated a high spatial resolutions using transmission electron microscopy, both by imaging and by chemical analysis. Transmission electron microscopy also makes possible the examination of reactions involving nitrate and ammonia in submicron individual particles. The proposed studies, taken together, will provide fine-scale data about a wide range of particle types that occur in the marine troposphere and that affect radiation backscatter and the microphysical properties of clouds.