Collaborative Research: Type 1 -- LOI02170139: Direct Statistical Approaches to Large-Scale Dynamics, Low Cloud Dynamics, and their Interaction

需要进行变革性研究，以实现气候建模的质量改进。研究人员正在开展一项跨学科的气候建模直接统计方法计划，该计划有可能极大地提高我们对不同气候过程如何在短期和长期时间尺度以及小型和大型空间尺度上相互作用的理解。该计划为一类新的气候模型奠定了基础，这些模型可能补充甚至最终取代现有的气候模型。它有两条平行的轨道。首先，研究人员正在开发直接计算气候统计数据的方法，这些方法最终可能取代传统的数值模拟，从而产生计算效率更高的气候模型。第二，他们正在改进低云的表示方法，并更好地了解云与大规模环流的相互作用，从而产生更准确的气候模型，并减少目前在云表示中存在的巨大不确定性。直接计算气候统计数据的方法是基于累积量展开，其中快速模式被整合出来。这使人们的注意力重新集中在评价和了解低频模态上，低频模态是气候变异的主要因素。基于云和次网格尺度动力学的概率闭合，开发了低云的改进表示，可以系统地提高精度。这些都被集成到一个大气环流模式（GCM），耦合云的大规模流动，允许它们的相互作用的系统研究。这项工作扩展了过去在相对简单的地球物理流模型中直接计算统计数据的工作，使其更加复杂和现实，同时提高了统计方法和GCM本身的准确性。

Transformative research is needed to realize qualitative improvements in the modeling of climate. The investigators are carrying out an interdisciplinary program of direct statistical approaches to climate modeling that has the potential to dramatically improve our understanding of how different climate processes interact over short and long time scales and small and large spatial scales. The program lays the foundations for a new class of climate models that may complement or even eventually replace existing climate models. It has two parallel tracks. First, the investigators are developing methods for the direct computation of climate statistics that may eventually replace conventional numerical simulations, leading to computationally more efficient climate models. Second, they are developing improved representations of low clouds and an improved understanding of cloud interactions with large-scale circulations, leading to more accurate climate models and reducing the currently large uncertainties in the representation of clouds in them. The methods for the direct computation of climate statistics are based upon cumulant expansions in which fast modes are integrated out. This refocuses attention on the evaluation and understanding of low-frequency modes, which dominate climate variability. Improved representations of low clouds are developed based on probabilistic closures of cloud and subgrid-scale dynamics, which can be systematically improved in accuracy. These are integrated into a general circulation model (GCM) that couples the clouds to the large-scale flows, allowing a systematic study of their interactions. The work extends past work on the direct computation of statistics in relatively simple models of geophysical flows to GCMs of increasing complexity and realism, while improving the accuracy of the statistical methods and of the GCMs themselves.