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特性。因此，这项研究解决了气候模拟中的一个主要不确定因素，即气溶胶对云层辐射特性的影响所产生的“间接效应”。预计粒子浓度越高，云滴越多，云层越亮，寿命越长，产生降水的可能性越小，但事实证明，很难根据这一预期来制定定量预测。在这项研究中，研究人员将尝试将预计影响显著的案例分离出来，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分开。这项工作需要几个模型的耦合，以表示真实的云场、云元素、云滴大小以及化学和气溶胶传输。然后，这个耦合模型将应用于德克萨斯州休斯敦的合适条件，那里有严重的城市污染，预计会影响形成城市顺风向云的特性。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，因此最终需要扩展到其他类型的云，这些类型也会影响全球辐射平衡。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.