Numerical Climate Modeling and Water Vapor Feedback

正在研究的问题是气候变化将如何影响水蒸气反馈，并反过来受到水蒸气反馈的影响。PI将试图回答的主要问题是：（1）为什么全球气候模式（GCMs）产生的水汽反馈与热力学参数雅阁，而其他一些模式却不能做到这一点;什么类型的模式在解决这个问题时是值得信赖的，以及出于什么物理原因;以及对流层上层的相对湿度会随气候变化而保持不变，还是如最近一些研究所建议的随暖化而减少？这些问题将通过大气GCM（AGCM）气候变化实验来解决，对模型进行微观物理和宏观物理改变。共同体气候系统模式（CCSM）大气部分（CAM）将适用于这一用途。通过该项目启动的建模能力也将用于与耶鲁大学其他教师在古气候问题上的合作研究，并将提供给耶鲁大学社区的学生和教育使用。由于计算成本不断下降，为此类项目建立全球模型的组成部分已变得越来越可行。这项研究旨在解决一些长期存在的和有争议的问题，围绕小与大尺度过程在确定全球湿度的重要性，以及在对流流出水平的热带对流层顶附近的水物种的运输。 更广泛的影响：研究结果应该会提高对气候变化模型预测的信心，或者对最需要开展工作的领域提出更有针对性的想法。无论哪种结果，最终都将提高气候预测对社会和政策考虑的有用性。此外，这一努力应有助于在相关研究领域（生态和社会影响、古气候等）更多地使用定量和严格的气候计算。

The problem being studied is how a changing climate will affect and be affected in turn by water vapor feedbacks. The main questions the PI will try to answer are: (1)why do global climate models (GCMs) produce water vapor feedback in accord with thermodynamic arguments, while some other models fail to do so; what types of models are trustworthy in addressing this issue, and for what physical reasons; and, will relative humidity in the upper troposphere stay constant as climate changes, or decrease with warming as suggested by some recent studies? These questions will be addressed through atmospheric GCMs (AGCM) climate-change experiments with microphysical and macrophysical alterations to the model. The Community Climate System Model (CCSM) atmospheric component (CAM) will be adapted for this use. The modeling capabilities initiated through this project will also be used for collaborative research with other Yale faculty on paleoclimate questions, and will be made available for student and educational use to the Yale community. A global modeling component to such projects has become increasingly feasible owing to the steadily declining costs of computing. This research aims to resolve some longstanding and controversial questions surrounding the importance of small vs. large-scale processes in determining global humidity, and the transport of water species near the tropical tropopause at convective outflow levels. Broader Impacts: Results should lead either to improved confidence in model forecasts of climate change, or else a more focused idea of where work is most needed. Either result would ultimately improve the usefulness of climate forecasts for societal and policy consideration. Also, this effort should facilitate greater use of quantitative and rigorous climate calculations in related research areas (ecological and societal impacts, paleoclimate, etc.).