Quantifying the Effects of Aerosols on Climate, and Their Behaviour in the Atmosphere

大气气溶胶——悬浮在空气中的小颗粒——包括海盐（来自破碎的波浪）、风吹来的灰尘、硫酸盐和来自自然和人为来源的有机化合物。气溶胶可以影响地球的太阳辐射收支，首先是通过散射和吸收入射的太阳辐射和流出的地面辐射（直接效应）。其次，气溶胶可以通过改变水滴的数量（间接效应）来影响云的光学特性——云层既将太阳辐射散射回太空，又吸收向外发射的长波辐射。气溶胶对地球表面温度影响的总强度与温室气体（主要是二氧化碳）相似，但据信是净降温而非净升温。然而，这种影响的确切大小是非常不确定的。气溶胶颗粒还影响人类健康，并为发生化学反应提供表面，其中许多对确定有害的表面臭氧浓度很重要。英国气象局进行气候研究，并联合领导一个计划，建立和评估一个新的全球计算机模型，适用于气候和环境变化研究的一系列主题。关键任务之一是改进模型中大气气溶胶及其影响的表征。重要的气溶胶特性包括气溶胶颗粒对大气相对湿度和温度变化的吸水性，气溶胶颗粒的大小，以及气溶胶与周围挥发性化合物（如氨、硝酸和一些有机化合物）气相之间的分配。在计算机模型中改进对气溶胶的处理是更准确地表示气溶胶的直接和间接影响、改进气候变化预测和制定有效的适应和补救公共政策的必要步骤。这个项目帮助气象局完成这项任务。大气气溶胶的形成、性质和行为目前是实验室、实地测量活动和世界各地建模人员积极研究的主题。英国气象局在气体/气溶胶的详细热力学方面没有专门知识，这可以用来开发和测试新的气溶胶方案，这些方案可以纳入他们的气候模型。这个知识转移项目的主要目的是通过提供基于网络的工具，结合我们在5年多的时间里开发的最先进的气溶胶模型，来解决这一差距。它们体现了国际公认的对流层和平流层气溶胶系统组分行为的研究结果。它们将使英国气象局能够评估和测试其全球气候和其他模式中气溶胶特性的表征，指导其未来的发展，并最终减少与气溶胶对气候变化影响相关的不确定性。这些基于网络的工具可以免费使用，我们过去的经验表明，它们很可能用于全世界的气溶胶科学研究和教学。

Summary for General Audience Atmospheric aerosols - small particles suspended in the air - include seasalt (from breaking waves), wind-blown dust, and sulphates and organic compounds from both natural and anthropogenic sources. Aerosols can affect the earth's budget of solar radiation, first, by scattering and absorbing incoming solar and outgoing terrestrial radiation (the direct effect). Second, aerosols can affect the optical properties of clouds - which both scatter solar radiation back to space, and absorb outgoing long wave radiation - by changing the numbers of water droplets present (the indirect effect). The total magnitude of the aerosol effect on the surface temperature of the earth is similar to that of the greenhouse gases (mainly CO2), but is believed to be a net cooling rather than warming. However, the exact size of the effect is very uncertain. Aerosol particles also affect human health and provide surfaces for chemical reactions to take place on, many of which are important in determining the concentration of surface ozone which is harmful. The U.K. Meteorological Office carries out climate research and is the joint leader of a programme to build and evaluate a new global computer model suitable for a range of topics in climate and environmental change research. One of the key tasks is to improve the representation of atmospheric aerosols and their effects in the model. Important aerosol properties include the uptake of water by the aerosol particles in response to atmospheric relative humidity and temperature changes, the size of the aerosol particles, and the partitioning between the aerosols and surrounding gas phase of volatile compounds such as ammonia, nitric acid, and some organic compounds. Improving the treatment of aerosols in the computer model is an essential step to representing both the direct and indirect aerosol effects more accurately, and to making improved climate change predictions, and formulating effective public policy for adaptation and remediation. This project assists the Met Office in this task. The formation, properties, and behaviour of atmospheric aerosols are currently the subject of active investigation in the laboratory, by field measurement campaigns, and by modellers around the world. The Met Office does not have expertise in the detailed thermodynamics of gas/aerosol which can be used to develop and test new aerosol schemes that can be incorporated into their climate model. The primary purpose of this knowledge transfer project is to address this gap by providing web-based tools incorporating state-of-the-art aerosol models developed by us over a period of more than 5 years. These embody the results of internationally recognized research into the behaviour of the components of tropospheric and stratospheric aerosol systems. They will enable the Met Office to evaluate and test representation of aerosol properties in their global climate and other models, guide their future development, and ultimately reduce the uncertainties associated with the aerosol influence on climate change. These web-based tools can be accessed freely, and our past experience demonstrates that they are likely to be used in aerosol science research and teaching worldwide.