A Physics Coupler for Climate Models

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。气候在很大程度上取决于与云有关的过程。尽管如此，在当前的气候模式中，与云相关的过程通常仅通过网格盒方式相互作用，而不是在小尺度上直接相互作用。例如，让小尺度云结构的充分变率直接驱动降水过程，让降水反过来直接改变小尺度云结构是可取的。缺乏这样一个接口导致各种云相关过程的模拟降低。为了满足这一需求，该项目将开发一种基于假设概率密度函数（PDF）方法的物理耦合器。假定的PDF方法通过放大局部过程速率来产生降水速率的格框平均值。过去，对小尺度变率进行平均的方法有两种：(1)解析积分，或(2)拉丁超立方体采样，这是一种蒙特卡罗积分。这两种方法都有缺点。研究人员将开发一种新的方法来减少噪音，同时允许使用复杂的降水方案。该技术将在气候模型中实施，并用于模拟云，并可能在未来的工作中导致一个广义的物理耦合器，将改善气候模拟的许多方面。这项工作的广泛影响包括与现实世界的软件工程本科院校建立伙伴关系，广泛培训研究生和教学，以及在社区传播研究并造福社会。虽然这项研究的目的是立即应用于气候模式中的降水过程，但这些技术将来可能会应用于其他模式类型，如数值天气预报模式和其他物理现象，如大气化学。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Climate depends strongly on processes related to clouds. Despite this, in current generation climate models, cloud-related processes typically interact with each other only through grid box means and not directly with each other on the small scales. For instance, it would be desirable to let the full variability in small-scale cloud structure directly drive precipitation processes and let precipitation in turn directly alter the small-scale cloud structure. The lack of such an interface leads to degraded simulations of a variety of cloud related processes. To address this need, the project will develop a physics coupler based on the assumed probability density function (PDF) method. The assumed PDF method produces grid box averages of precipitation rates by upscaling local process rates. In the past, the averaging over the small-scale variability has been performed by either of two methods: (1) analytic integration, or (2) Latin hypercube sampling, which is a type of Monte-Carlo integration. Both methods suffer drawbacks. The investigator will develop a new approach to reduce noise while permitting the use of sophisticated precipitation schemes. The technique will be implemented in a climate model and used to simulate clouds, and may lead, in future work, to a generalized physics coupler that will improve many facets of climate simulations.Broader impacts of this work include partnership with an undergraduate institution in real-world software engineering, broad training of graduate students and teaching, and disseminating research in the community and benefiting society. Although the research is intended to have immediate application to precipitation processes in climate models, the techniques may be applied in the future to other model types, such as numerical weather prediction models, and other physical phenomena, such as atmospheric chemistry.