Ice Nucleation in Cirrus Clouds: Anthropogenic Climate Forcing and Uncertainties

卷云中的冰核：人为气候强迫和不确定性

• 批准号: 1540954
• 负责人: Joyce Penner
• 金额: $ 57.26万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1540954&HistoricalAwards=false
• 关键词: Ice; Nucleation; Cirrus; Clouds; Anthropogenic

This research focuses on the use of a global chemistry/climate model to improve the modeling of ice formation in cirrus clouds. This research will better inform climate modelers about the causes of differences in model predictions of the effects of small particles (aerosol) in cirrus clouds. It will also provide a representation of aerosol and ice formation that is based on physical and chemical processes and broadly consistent with the field observations used to evaluate the model.The researchers hypothesize that a substantial fraction of ice formation in cirrus clouds is associated with secondary organic aerosols (SOA) and/or solid ammonium sulfate (NH4)2SO4 and that changes in these aerosols over time result in a significant climate forcing. The hypothesis will be tested using the Community Atmosphere Model (CAM5) climate model coupled to the IMPACT aerosol model. The IMPACT model ties the formation of SOA to the photochemical oxidation of volatile organic compounds (VOCs) based on a recently extended oxidation scheme. The researchers are in the process of extending the SOA formation framework to allow it to consider how the formation mechanism alters the size distribution of both primary organics and other aerosol species associated with SOA. In this research, they will explore several ways of parameterizing SOA nucleation. They will compare the changes in SOA formation and forcing in cirrus clouds using varying amounts of dust, sulfate, glassy organic aerosols (depending on the glass transition temperature of each SOA), and solid (NH4)2SO4. The model simulations will be compared with observations from recent measurement campaigns to identify which treatments of SOA formation, ice cloud nucleation, and updraft velocities are best able to reproduce the observations. This research will better inform the climate community of the causes of differences in model predictions of aerosol effects in cirrus clouds. The results of this research will aid in quantifying climate forcing by aerosols and help to inform policy makers of the possible role of aerosols in either heating or cooling climate through their action in nucleating ice crystals.

这项研究的重点是使用全球化学/气候模式，以提高卷云冰形成的建模。 这项研究将更好地告知气候建模者关于卷云中小颗粒（气溶胶）影响的模型预测差异的原因。它还将提供一个基于物理和化学过程的气溶胶和冰形成的代表性，并与用于评估模型的实地观测大致一致。研究人员假设卷云中的冰形成的很大一部分与二次有机气溶胶（SOA）和/或固体硫酸铵（NH 4）有关。2SO 4和这些气溶胶随时间的变化导致了显着的气候强迫。将使用与IMPACT气溶胶模式耦合的社区大气模式（CAM 5）气候模式对这一假设进行检验。 IMPACT模型将SOA的形成与挥发性有机化合物（VOCs）的光化学氧化联系在一起，该模型基于最近扩展的氧化方案。 研究人员正在扩展SOA形成框架，以考虑形成机制如何改变与SOA相关的主要有机物和其他气溶胶物种的尺寸分布。在这项研究中，他们将探索参数化SOA成核的几种方法。他们将使用不同数量的灰尘，硫酸盐，玻璃状有机气溶胶（取决于每个SOA的玻璃化转变温度）和固体（NH 4）2SO 4来比较SOA形成和卷云强迫的变化。模型模拟将与最近的测量活动的观测结果进行比较，以确定SOA的形成，冰云成核和上升气流速度的治疗是最好的能够再现的观测。 这项研究将更好地告知气候界卷云气溶胶效应模型预测差异的原因。 这项研究的结果将有助于量化气溶胶的气候强迫，并有助于告知政策制定者气溶胶在加热或冷却气候中的可能作用，通过它们在冰晶成核中的作用。