Center for Clouds, Chemistry and Climate

大气的化学成分正在发生重大变化，这不仅是由于自然原因，而且也是由于人类活动。人类活动排放的污染物使几种微量气体的浓度显著增加。据预测，这个无意的实验将对空气化学和气候产生深远的影响。云、化学和气候中心（C4）的基本目标是发展观测和模拟基础，以了解和预测气候和空气化学的变化。气候化学相互作用、云在这种相互作用中的作用、全球模式中对云的现实处理以及人类活动的作用是主要的研究主题。该中心的多机构结构包括大学、欧洲机构、联邦实验室和工业界，将促进来自不同学科的小组之间前所未有的交流，并加速这些机构的研究进展。提出的研究将促进我们对微观尺度和宏观尺度如何相互作用的认识，并促进全球模式对云的处理。这些根本性的进步将有助于改进对人类对环境影响的预测，并有助于更好地了解区域天气和气候现象，包括温室气体变暖导致的全球气候变化。本研究的实用性和相关性非常高。正如工业界的参与所表明的那样，为本项目开发的实验方法（数据处理和图像处理）具有直接的技术相关性。云的作用是该中心的基本统一主题，该中心汇集了来自美国和欧洲几个机构的科学家，他们参与了化学、微物理、辐射、非线性动力学、天气和气候的研究。重要的区域尺度气候变化与云有关，因为云控制着降水、阳光、生物圈上的紫外线照射、土壤湿度和大气中化学物质的去除。云的辐射效应是如此之大，以至于云量的几个百分点的变化就足以将上个世纪增加的微量气体的温室效应放大或改善两倍。甚至这些变化的迹象都是未知的。在全局模型中，云是处理得最糟糕的特征。云在气候和化学中的不确定作用是处理全球变化问题中的一个棘手问题。云的形成是由于微观尺度和宏观尺度上化学、辐射、热力学和动力学之间的相互作用，它们反过来在行星尺度上显著影响这些过程。在阳光照射下，云滴中发生化学反应，将硫和氮化合物转化为硫酸和硝酸，这些化合物被毫米或更大的雨滴清除。深云将短期污染物从表层迅速输送到对流层上层，从而将局部问题转变为全球性问题。要更全面地了解云现象，需要进行一系列复杂的相互关联的观测，从实验室测量、对单云的飞机观测到对全球的卫星观测。它需要微物理模型来理解单个云滴与全局模型之间的相互作用，以解开云反馈问题。它还需要一个专门的小组来跨越学科界限进行合作。拟议的研究将解决所有这些要求。将对大量卫星数据进行分析，以确定硫化学与气候之间的联系，并阐明云辐射动力相互作用在诸如1982/83年厄尔尼诺现象和1988年炎热夏季等重大气候事件中的作用。全球化学和气候模型将用于了解原始和污染环境中氮氧化物、甲烷、其他碳氢化合物和臭氧之间的化学耦合。高分辨率雷达和卫星观测将与微物理和区域尺度模型结合使用，以了解单个云的聚集如何影响区域尺度的气候和化学。C4科学家还将参与实地测量，以开发和验证化学和气候模型。拟议研究的有用结果包括：生物圈紫外线辐照度的全球分布；上世纪人为辐射强迫的区域分布；改进全球模式对云的处理；以及区域变化的预测。暑期课程和研讨会将面向高中和大学的科学教师和其他学生。这项拓展工作将利用目前在芝加哥地区开展的有效教育项目。

The chemistry of the atmosphere is undergoing significant changes, not only due to natural causes, but also due to human activities. The emissions of pollutants by human activities have caused significant increases in the concentration of several trace gases. This inadvertent experiment is predicted to have profound effects on air-chemistry and climate. The basic goal of the Center for Clouds, Chemistry and Climate (C4) is to develop the observational and the modeling base to understand and to predict the changing climate and air-chemistry. Climate-chemistry interactions, the role of clouds in such interactions, realistic treatment of clouds in global models and the role of human activities are the major research themes. The multi-institutional structure of the center involving universities, European institutions, federal labs and industries will facilitate unprecedented cross-fertilization between groups from diverse disciplines and accelerate the progress of research in these institutions. The proposed research should advance our knowledge of how micro-and macroscales interact and advance the treatment of clouds in global models. These fundamental advances should lead to improved predictions of the human impacts on the environment and to a better understanding of regional weather and climate phenomena, including global climate change by greenhouse gas warming. The utility and relevance of the research is very high. As indicated by the participation of industry, there is immediate technological relevance of experimental methods (data handling and image processing) developed for this project. The role of clouds is the fundamental unifying theme of the center which brings together scientists from several institutions in the U.S. and Europe who are involved in the study of chemistry, microphysics, radiation, nonlinear dynamics, weather and climate. Important regional scale climate changes are associated with clouds since they govern the rate of precipitation, sunlight, UV irradiance on the biosphere, soil moisture and removal of chemicals from the atmosphere. The radiative effects of clouds are so large that just a few percent change in cloudiness is sufficient to amplify or ameliorate by a factor of two the greenhouse effect of the trace gas increases during the last century. Even the sign of such changes are unknown. Clouds are the most poorly treated features in global models. The uncertain role of clouds in climate and chemistry is a Gordian knot of problems dealing with global changes. Clouds form because of microscale and macroscale interactions between chemistry, radiation, thermodynamics and dynamics and they in turn influence these processes significantly on the planetary scale. In the presence of sunlight, chemical reactions take place in cloud droplets converting sulfur and nitrogen compounds to sulfuric and nitric acids which are scavenged out by millimeter and larger sized rain drops. Deep clouds rapidly transport short-lived pollutants form the surface layer to the upper troposphere thus transferring a local problem into a global one. A fuller understanding of cloud phenomena requires a complex array of interrelated observations ranging from laboratory measurements, aircraft observations of a single cloud to satellite observations of the whole globe. It requires microphysical models to understand the interactions within a single cloud droplet to global models to unravel cloud feedback problems. It also requires a dedicated group to collaborate across disciplinary boundaries. The proposed research will address all of these requirements. Large volumes of satellite data will be analyzed to establish the link between sulfur chemistry and climate and to unravel the role of cloud radiative-dynamical interactions in major climate events such as the El-Nino of 1982/83 and the severe summer of 1988. Global models of chemistry and climate will be employed to understand the chemical coupling between nitrogen oxides, methane, other hydrocarbons and ozone in pristine and polluted environments. High resolution radar and satellite observations will be used in conjunction with microphysical and regional scale models to understand how the effects of individual clouds aggregate to govern regional scale climate and chemistry. C4 scientists will also participate in field measurements to develop and verify models of chemistry and climate. Useful results from the proposed research include: global distribution of UV irradiance on the biosphere; regional distributions of the anthropogenic radiative forcing during the last century; improved treatment of clouds in global models; and prediction of regional changes. Summer courses and workshops will be conducted to reach out to high school and college science teachers and other students. This outreach effort will take advantage of the effective educational programs currently in operation in the Chicago area.