Sustainability: Atmospheric Physics Needs for Community Climate Modeling

地球系统模型（esm）服务于一系列目的。尖端的esm用于生成未来几十年的气候预测，但它们也被研究界用作工具，以了解地球系统内发生的过程和相互作用。esm的尖端组件在复杂性和计算费用方面继续增长，这是改进未来气候预测的必要演变，但同时，这降低了计算资源有限的研究人员执行有针对性的实验来解决他们感兴趣的问题的能力。因此，在esm中，计算简化但仍然现实的选项可以发挥重要作用。社区地球系统模型（Community Earth System Model， CESM）是一种在美国和世界范围内广泛应用的ESM模型。CESM的目标不仅是产生尖端的气候预测，而且为研究界提供必要的工具，以获得对地球系统行为的基本理解。社区大气模式（Community Atmosphere Model， CAM）的大气分量是社区大气模式中计算成本最高的分量之一。CAM正在走向一个新的框架，用于将物理参数化连接到主机模型，以便简化新的物理包的实现。然而，这意味着一些可以用来构建更便宜的大气模型以获得基本理解的物理参数化将会丢失，除非它们可以被重构以与这个新框架兼容。这项工作将重构CAM中的前几代大气物理包，使它们能够在CESM中保持功能，并继续作为全球研究人员的重要资源使用。这种重构将伴随着文档和教程的开发，这些文档和教程将允许用户使用他们自己选择的物理参数化来配置和设置他们的模型模拟，这些参数化可以平衡复杂性和计算费用，以满足他们的需求。这将使CESM能够继续支持广泛和多样化的用户群，并提供一个教育工具，使个人能够以最小的计算费用获得实际的气候建模经验。Common Community Physics Package （CCPP）是一个框架，旨在促进大气模型中物理套件或单个参数化的实现。在不久的将来，CAM将独家使用该框架，这意味着任何未重构为与CCPP兼容的物理参数化将不再供CESM的研究社区使用。这项工作将重构前几代CAM物理（CAM4和CAM5）的关键组件，使研究人员能够继续构建科学上接近CAM4和CAM5的大气配置，并且/或者将它们的功能与更新的物理参数化混合和匹配。这将确保这些物理参数化在CESM中保持功能，从而将它们保留为地球系统研究界重要的、但在计算上精简的研究工具。CCPP框架包含一个符合选定标准的物理参数化库，以及一个允许将这些参数化连接到主机模型的基础设施。该项目将CAM4和CAM5物理参数化移植到CCPP框架。这个过程的一部分是实现显式接口，其中传入/传出参数化的变量在变量字典中定义，因为参数化不能再访问物理参数化之间的共享内存空间（在CAM中称为pbuf），所有变量都必须显式传递。因此，用户可以清楚地知道参数化使用了哪些变量（以及是否存在与其他参数化的隐式依赖关系），从而最终向主机模型提供趋势。为了在CCPP中实现这些物理参数化，将开发文档和教程，允许用户配置和设置与CAM4或CAM5非常相似的模型配置，或混合和匹配不同的物理参数化以满足其目的，从而填充大气模型层次结构，以支持广泛的研究目的。该合同由先进网络基础设施办公室颁发，并得到地球科学理事会大气和地球空间科学部的联合支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Earth System Models (ESMs) serve a range of purposes. Cutting edge ESMs are used to generate climate projections for the coming decades, but they are also used as tools by the research community to gain understanding of processes and interactions that occur within the Earth System. The cutting-edge components of ESMs continue to grow in complexity and computational expense, which is a necessary evolution for improving state-of-the-art projections of future climate, but at the same time, this reduces the ability of researchers with limited computational resources to perform targeted experiments to address their problem of interest. As such, there is an important role to be played by computationally streamlined, yet still realistic, options within ESMs. The Community Earth System Model (CESM) is an ESM that is widely used within the research community of the USA and worldwide. The aims of CESM are not only to produce cutting edge climate projections but to provide the necessary tools to the research community to gain fundamental understanding of the behavior of the Earth System. The atmospheric component of CESM (the Community Atmosphere Model, CAM) is one of the most computationally expensive components of CESM. CAM is moving toward a new framework for connecting physical parameterizations to the host model in order to simplify the implementation of new physics packages moving forward. However, this means that some physical parameterizations that can be used to build a cheaper atmospheric model for gaining fundamental understanding will be lost, unless they can be refactored to be compatible with this new framework. This work will refactor previous generations of atmospheric physics packages within CAM to allow them to remain functional within CESM and continue to be used as an important resource for researchers worldwide. This refactoring will be accompanied by the development of documentation and tutorials that will allow users to configure and set up their model simulations with their own choices of physical parameterizations that can balance complexity, with computational expense, to suit their needs. This will allow CESM to continue to support a broad and diverse user base and to provide an educational tool that can allow individuals to gain a hands-on climate modeling experience at minimal computational expense.The Common Community Physics Package (CCPP) is a framework that is designed to facilitate the implementation of physics suites or individual parameterizations in atmospheric models. CAM is moving toward exclusive use of this framework in the near future which means that any physical parameterizations that are not refactored to be compatible with CCPP will no longer be available to the research community within CESM. This work will refactor the key components of previous generations of CAM physics (CAM4 and CAM5) to allow researchers to continue to build atmospheric configurations that are scientifically close to CAM4 and CAM5 and/or mix and match their capabilities together with newer physical parameterizations. This will ensure that these physical parameterizations remain functional within CESM, thereby retaining them as important, yet computationally streamlined, research tools for the Earth System research community. The CCPP framework contains a library of physical parameterizations that conforms to selected standards, and an infrastructure that enables connection of these parameterizations to the host model. This project will port CAM4 and CAM5 physics parameterizations to the CCPP framework. Part of this process is to implement explicit interfaces where variables passed in/out of the parameterization are defined in a variable dictionary since the parameterization can no longer access shared memory spaces between physics parameterizations (known as pbuf’s in CAM) and all variables must be passed explicitly. Hence it will be clear to the user exactly what variables a parameterization is using (and if there are implicit dependencies to other parameterizations) to ultimately provide tendencies back to the host model. To accompany the implementation of these physical parameterizations within CCPP, documentation and tutorials will be developed that will allow users to configure and set up model configurations that closely resemble CAM4 or CAM5 or to mix and match different physical parameterizations to suite their purpose, thereby filling out the atmospheric model hierarchy to support a broad range of research purposes.This award by the Office of Advanced Cyberinfrastructure is jointly supported by the Division of Atmospheric and Geospace Sciences within the Directorate for Geosciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.