Interactions of Aerosols, Marine Boundary Layer Clouds, and Precipitation During the VOCALS-Regional Experiment: Observations, Modeling, and Large-scale Model Assessment

这支持了在美国季风系统海洋-云-大气-陆地研究区域实验（VOCALS-REx，简称REx）期间收集的分析。VOCALS-REx野外活动于2008年10月至11月在东南太平洋（SEP）上空进行，旨在提高对气溶胶、海洋边界层（MBL）云和该地区降水之间相互作用的理解。SEP在气候上很重要，因为它是世界上最大的亚热带层积云甲板的所在地，它通过将太阳辐射反射回太空来冷却气候。因此，SEP中云、气溶胶和降水之间的相互作用可以通过调节云量和云反照率而产生重要的气候效应。这里的研究继续了两个关键的REx主题：对开放细胞口袋（POCs）的研究，这是层积云甲板上的开口，云可能由于毛毛雨的形成而消散；海洋污染输送及其对SEP云和气溶胶特征的影响研究。在雷克斯期间使用NCAR C-130飞机对云滴浓度的观测显示，从智利海岸向近海延伸的大“钩子”特征，这可能是由于与铜冶炼厂和沿海城市的污染有关的高浓度云凝结核（CCN）。在这项资助下进行的研究使用了REx数据，其中大部分数据以前没有被分析过，以及为VOCALS模型评估（VOCA）准备的全球大气模型模拟数据，以及使用大涡模拟（LES）代码的数值实验，以更好地了解POCs， hook和SEP气溶胶-云的相互作用。解决了三个广泛的科学问题：1)自由对流层气溶胶源对VOCALS地区，特别是距离沿海污染源500公里以上的海洋地区的CCN和云滴数浓度有多重要？2)气溶胶的降水汇是否是清洁和污染地区CCN差异的主要正反馈，特别是对于钩子和POCs？3)包含气溶胶-云-降水相互作用的区域和全球化学-气候模式能真实地模拟hook和POCs吗？除了科学价值之外，由于SEP云在调节地球气候方面的重要作用，该项目具有更广泛的影响。因此，更好地了解气溶胶-云相互作用在确定云量和云亮度方面的作用，可以改进对气候变率和变化的理解和预测。此外，该项目还支持两名研究生，从而为该领域的下一代科学工作者提供支持。

This supports analysis of collected during the Variability of the American Monsoon Systems Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx, or simply REx). The VOCALS-REx field campaign took place over the Southeast Pacific Ocean (SEP) during Oct-Nov 2008, and was designed to improve understanding of interactions between aerosols, marine boundary layer (MBL) clouds, and precipitation over the region. The SEP is climatically important because it is home to the world's largest subtropical stratocumulus cloud deck, which cools the climate by reflecting solar radiation back to space. Thus interactions between clouds, aerosols, and precipitation in the SEP can have an important climatic effect by modulating cloud cover and cloud albedo. The research here continues two key REx themes: research on Pockets of Open Cells (POCs), which are openings in the stratocumulus deck in which clouds have presumably dissipated due to drizzle formation; and research on offshore transport of pollution and its effect on SEP cloud and aerosol characteristics. Observations of cloud droplet concentration taken during REx using the NCAR C-130 aircraft show large "hook" features extending offshore from the Chilean coast, which may be due to high concentrations of cloud condensation nuclei (CCN) associated with pollution from copper smelters and coastal conurbations.Research performed under this grant uses REx data, much of which has not been previously analyzed, as well as data from global atmospheric model simulations prepared for the VOCALS Model Assessment (VOCA), together with numerical experiments using a large-eddy simulation (LES) code, to develop a better understanding of POCs, hooks, and SEP aerosol-cloud interactions. Three broad science questions are addressed: 1) How important is the free-tropospheric aerosol source to CCN and cloud droplet number concentrations in the VOCALS region, especially in the oceanic region over 500 km away from coastal pollution sources? 2) Is the precipitation sink for aerosols a major positive feedback on CCN differences between clean and polluted regions, in particular for hooks and POCs? 3) Can regional and global chemistry-climate models that include some representation of aerosol-cloud- precipitation interactions realistically simulate hooks and POCs?Beyond its scientific merit, the project has broader impacts due to the important role of SEP clouds in regulating earth's climate. A better understanding of the role of aerosol-cloud interactions in determining cloud cover and cloud brightness could thus lead to improved understanding and predictions of climate variability and change. In addition, the project supports two graduate students, thereby providing for the next generation of the scientific workforce in this area.