Direct Validated Improvement of Atmospheric Aerosol Property Prediction Using Laboratory Measurements

气溶胶粒子通过太阳辐射的散射和吸收直接影响气候（直接影响），通过它们作为云凝结核的作用间接影响气候（间接影响），后一种影响构成气候变化中最大的不确定性。同样，气溶胶颗粒对空气质量也有很大的影响。不幸的是，有许多不确定因素妨碍了我们模拟气溶胶粒子的行为，从而评估它们可能产生的影响。这些不确定性主要是由有机化合物的复杂性引起的，有机化合物占化学成分的很大一部分，随后与无机化合物偶联。虽然物种形成很困难，但我们知道某些化合物存在于这个部分中，但缺乏针对特定参数的详细实验室/理论研究。如果不提高对基本数据的了解，就不可能以任何程度的确定性预测影响或简化和/或参数化气溶胶特性。然而，旨在评估气溶胶对气候影响的大尺度模式的发展，例如，严重依赖于这种参数化。因此，目前无法获得的数据会导致气溶胶影响的不确定性。最重要的不确定性是那些决定气溶胶含水量和气体/气溶胶分配的参数。前者是预测直接和间接气候效应的必要条件；后者决定了气溶胶的化学成分的演变，因此对于预测气溶胶的负荷和成分是必要的，这对考虑空气质量也很重要。为了确定在100%相对湿度下对水吸收的影响，需要通过测量/预测水活度来研究水热力学，水活度代表“有效”浓度。对于100%RH以上的吸水性预测，溶液表面张力是预测云活化的关键参数。在描述气溶胶颗粒组成的变化时，重要的是要知道化合物在气相和颗粒相之间的分裂有多容易。这里有两个参数很重要。溶质活度系数是测量溶液中发生的化学相互作用的一种方法，它描述了化合物在水溶液气溶胶中的“舒适程度”，因此对于模拟冷凝非常重要。同样，低蒸汽压的化合物更倾向于分解为气溶胶粒子，因此是一个重要的参数，但仍然高度不确定。本提案旨在利用成熟的技术，对关键参数进行一系列详细的实验室测量，这些参数目前严重损害了最先进的多组分气溶胶行为模型的预测能力。因此，来自实验室方案的基础模型和预测技术的改进将直接用于改进气候预测和空气质量评估。

Aerosol particles influence climate directly by the scattering and absorption of solar radiation (direct effect) and indirectly through their role as cloud condensation nuclei (indirect effect), the latter effect comprising the largest uncertainty in climate change. Similarly, aerosol particles have a large impact on air quality. Unfortunately, there are many uncertainties which hinder our ability to model the behaviour of aerosol particles and thus asses the impacts they can have. These uncertainties are largely caused by the complexity of organic compounds, which represent a significant fraction of the chemical composition, and subsequent coupling with inorganic compounds. Whilst speciation is difficult we know certain compounds reside in this fraction yet detailed laboratory/theoretical studies focusing on specific parameters are lacking. Without an improved knowledge of basic data it is not possible to predict effects or simplify and / or parameterise aerosol properties with any degree of certainty. However, development of large scale models which aim to assess the effect of aerosols on climate, for example, rely heavily on such parameterisations. Thus, current unavailability of data propagates through to uncertainty in the aerosol impact. The most important uncertainties are in those parameters which dictate the aerosol water content and gas / aerosol partitioning. The former is necessary for predicting the direct and indirect climatic effect; the latter determines the evolving chemical composition of the aerosol and hence is necessary for predicting aerosol loading and composition which is also important for air quality considerations. To determine effects on water uptake below 100% relative humidity, investigations of aqueous thermodynamics are required through measurements / predictions of a quantity known as the water activity, which represents an 'effective' concentration. For predictions of water uptake above 100%RH, the solution surface tension is a crucial parameter for predictions of cloud activation. In describing the changing composition of aerosol particles, it is important to know how readily a compound will partition between the gas and particulate phase. Two parameters are important here. Solute activity coefficients, a measure of chemical interactions taking place in solution, describes how 'comfortable' a compound is in the aqueous aerosol, and is thus important for modelling condensation. Similarly, compounds with low vapour pressure have higher tendency to partition to aerosol particle and is thus an important parameter yet remains highly uncertain. This proposal seeks to conduct a range of detailed laboratory measurements, using well-established techniques, on key parameters which at the present time critically compromise the predictive capability of state of the art models of multicomponent aerosol behaviour. Improvement in the base models and predictive techniques from the laboratory programme will thus find its way directly to improved climate predictions and assesment of air quality.