Collaborative Research: Demonstration of a New Framework for Studying Aerosol Indirect Effects

这些研究人员将使用一种新的耦合模型来研究气溶胶如何影响云的性质。因此，这项研究解决了气候模拟中的一个主要不确定因素，即气溶胶对云的辐射特性的影响所产生的“间接效应”。粒子浓度越高，云滴越多，云越亮，云的寿命越长，产生降水的可能性越小，但根据这一预期很难进行定量预测。在这项研究中，研究人员将试图将影响预计会突出的情况分离出来，然后使用他们的模型将气溶胶对这些云的影响与也影响相同云特性的其他因素区分开来。这项工作需要几个模型的耦合，以表示真实的云场、云要素、云滴大小以及化学和气溶胶运输。然后，这个耦合模型将适用于德克萨斯州休斯顿的情况，那里有严重的城市污染，预计会影响城市下风形成的云的性质。这项研究的预期结果将是评估城市污染或其他气溶胶来源如何影响云的特性，如反射率、形成降水的概率和寿命。这项研究的成果将适用于积云，因此需要最终扩展到其他也影响全球辐射平衡的云类型。气候科学家需要这些信息，他们试图预测大气中不断增加的气溶胶含量将如何影响地球的辐射平衡和降水分布。

These investigators will use a new coupled model to study how aerosols influence the properties of clouds. This study thus addresses one of the major uncertainties in climate simulations, the "indirect effect of aerosols" that arising from their influence on the radiative properties of clouds. It is expected that higher concentrations of particles lead to more cloud droplets and so to brighter clouds as well as clouds with longer lifetime and reduced probability of producing precipitation, but it has proven difficult to formulate a quantitative prediction based on this expectation. In this study, the investigators will attempt to isolate cases where the influence is expected to be prominent and will then use their model to separate the influence of aerosols on those clouds from other factors that also affect the same cloud properties. The effort requires coupling of several models in order to represent realistic cloud fields, cloud elements, cloud-droplet sizes, and chemical and aerosol transport. This coupled model will then be applied to conditions appropriate for Houston, Texas, where there is significant urban pollution expected to affect the properties of clouds that form downwind of the city.The expected result of this research will be an assessment of how urban pollution or other sources of aerosols affects cloud properties like reflectivity, probability of forming precipitation, and lifetime. The product of this research will apply to Cumulus clouds, and so will need eventual extension to other cloud types that also influence the global radiation balance. This information is needed by climate scientists who seek to predict how the increasing aerosol content of the atmosphere will affect the radiative balance and the precipitation distribution of the Earth.