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

该项目是将于2004-2005年在安提瓜和巴布达进行的关于暖雨形成和信风积云特征的多调查者研究的更广泛的“海洋积云中的雨”实验的一个组成部分。这种云中的雨是在被称为“云凝结核”或CCN的粒子上凝结后形成的，其中一些被认为是部分由有机化合物组成的。然而，人们对CCN中的有机成分知之甚少，这是一个有争议的话题，因为在存在大量有机成分的情况下，标准的CCN测量可能无法提供有效的测量结果。这项研究项目的目的是确定热带海洋气溶胶的代表性浓度、粒度分布、组成、CCN活性和有机组分，并特别注意有机气溶胶对云特性的影响。将在三个地点收集过滤样本，其中两个在波多黎各，一个在靠近波多黎各实验区的巴布达，以便将自然和人为来源分开。对收集的样本的分析将由参与这项工作的化学家的国际合作进行。这项研究的其他组成部分包括测量被云层清除的颗粒的比例，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是决定热带云中液滴浓度和液滴大小的颗粒子集。了解这些粒子对云的影响是RICO的一个关键贡献，因为由此产生的液滴的大小影响云中降水的速度和效率，这是该实验研究的主要过程。这些结果在研究人类对气候的影响方面具有广泛的潜在意义，因为它们促进了对颗粒物影响的理解，包括人类产生的颗粒物或与空气污染有关的颗粒物对降雨的影响。该项目还通过吸收波多黎各大学的调查人员和学生，使当地很好地参与了(将在安提瓜和巴布达进行的)里科实验。在实地实验期间举办的研究生研讨会将为这所大学和其他大学的学生提供教育机会，并将有助于推进这一领域的培训，特别是这所大学以西班牙裔为主的学生。为这项工作购置的新设备也将使相关研究能够在该机构继续进行。

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.