Tropical Marine Aerosols in the Trade Winds: Towards a Better Understanding of the Role of Organic Aerosols in Cloud Condensation Nuclei (CCN)

该项目是更广泛的“海洋积云中的雨”（RICO）实验的一个组成部分，该实验是2004-2005年在安提瓜和巴布达进行的一项关于暖雨形成和信风积云特征的多研究者研究。这种云中的雨是在被称为“云凝结核”（CCN）的粒子凝结后形成的，其中一些被认为部分由有机化合物组成。然而，对CCN中的有机成分知之甚少，这是一个有争议的话题，因为标准CCN测量可能无法在存在大量有机成分的情况下提供有效的测量。本研究项目的目的是确定热带海洋气溶胶的代表性浓度、大小分布、组成、CCN活性和有机组分，特别注意有机气溶胶对云性质的影响。将在三个地点收集过滤器样本，两个在波多黎各，一个在波多黎各实验区附近的巴布达，以便分离自然和人为来源。对收集的样品的分析将由参与这项工作的国际化学家合作进行。该研究的其他组成部分包括测量被云清除的颗粒的比例，以及研究水溶性有机碳对溶液液滴表面张力的可能影响。该项目有可能帮助确定有机成分是否对CCN有重大影响，CCN是决定热带云层中液滴浓度和液滴大小的粒子子集。了解这种颗粒对云的影响是对RICO的一个关键贡献，因为由此产生的液滴的大小影响云降水的速率和效率，这是该实验正在研究的主要过程。这些结果对研究人类活动对气候的影响具有广泛的潜在影响，因为它们促进了对颗粒（包括人类产生的颗粒或与空气污染有关的颗粒）对降雨的影响的认识。该项目还通过包括波多黎各大学的调查人员和学生，使当地积极参与RICO实验（将在安提瓜和巴布达进行）。在实地实验期间举办的研究生研讨会将为该大学和其他大学的学生提供教育机会，并将有助于推进该领域的培训，特别是对该大学主要的西班牙裔学生有利。为这项工作购置的新设备也将使该机构能够继续进行相关研究。

This project is a component of the broader "Rain in Cumulus Over the Ocean" (RICO) experiment, a multi-investigator study of warm-rain formation and the characteristics of trade-wind Cumuli to be conducted in Antigua-Barbuda in 2004-2005. Rain in such clouds forms after condensation on particles called "cloud condensation nuclei," or CCN, some of which are thought to be partly composed of organic compounds. However, little is known about the organic components in CCN, and this is a controversial topic because standard CCN measurements may not provide valid measurements in cases where there is a substantial organic component. The objective of this research project is to determine representative concentrations, size distributions, composition, CCN activity, and organic fraction for tropical marine aerosols, with particular attention to the influence of organic aerosols on the properties of clouds. Filter samples will be collected at three sites, two in Puerto Rico and one at Barbuda near the RICO experimental area, so that natural and anthropogenic sources can be separated. Analyses of the collected samples will be performed by an international collaboration of chemists who will be participating in this work. Other components of the study include measurement of the fraction of particles scavenged by clouds and study of possible effects of water-soluble organic carbon on the surface tension of solution droplets.The project has the potential to help determine if organic constituents have a significant influence on CCN, the subset of particles that determines the droplet concentration and droplet size in tropical clouds. Understanding the influence of such particles on clouds is a key contribution to RICO because the sizes of the droplets that result influence the rate and efficiency of precipitation from the clouds, the primary processes being studied by that experiment. The results have far-ranging potential implications in studies of anthropogenic influences on climate because they advance understanding of the effects of particles, including those produced by humans or those associated with air pollution, on rainfall. The project also brings good local involvement into the RICO experiment (to be conducted in Antigua-Barbuda) by including investigators and students from the University of Puerto Rico. A Graduate Student seminar conducted during the field experiment will provide educational opportunities for students from this university and others and will help advance training in this area, with particular benefits for the predominantly Hispanic students at this university. New equipment to be acquired for this work will also enable related studies to continue at this institution.