Collaborative Research: Enabling Cloud-Permitting and Coupled Climate Modeling via Nonhydrostatic Extensions of the CESM Spectral Element Dynamical Core

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Earth System Models (ESMs) are very computationally intensive to run, with components spanning the atmosphere, ocean, land, biosphere, and ice. These models are typically run at resolutions which are too coarse to explicitly represent weather systems like thunderstorm complexes, tropical cyclones, and terrain-forced precipitation. However, computing power is now sufficient to allow explicit simulation of these systems on a global domain using grid spacings of a few kilometers, albeit for simulations of weeks to months rather than the decades to centuries possible at lower resolutions. In this project, the research team will enhance the Community Earth System Model (CESM), led by the NSF National Center for Atmospheric Research (NCAR), with the capability to run as a Global Storm Resolving Model (GSRM). The GSRM version of CESM has tremendous potential as a tool for research on the weather-climate interface, particularly as CESM has a worldwide community of developers and users and is the primary model used by the US academic research community. As part of the project, multiple students and early career scientists would be trained at the intersection of atmospheric science and high-performance computing, enhancing a workforce that is crucially needed for scientific advancement.The main objective of the project is to lay the groundwork for simulations with CESM, which is comprised of individual models including the Community Atmosphere Model, for which version 7 (CAM7) is currently under development for release in 2024. CAM7's dynamical core uses the Spectral Element (SE) method to solve the equations of fluid motion under the hydrostatic approximation, in which the acceleration term is neglected in the vertical momentum equation. This project will port the nonhydrostatic SE dynamical core developed for the Department of Energy’s (DOE’s) Energy Exascale Earth System Model (E3SM) into CESM/CAM7. A second, more experimental version of the SE dynamical core meant to run on advanced computing architectures will also be ported. The researchers will then run CAM7 to test the ability to reproduce smaller-scale phenomena. Specifically, the project will: • Port DOE’s nonhydrostatic, Fortran-based, SE dynamical core into the CESM framework.• Integrate an experimental C++ version of the SE core into CESM with a GPU-enabled physics package from the NSF-funded EarthWorks project.• Test and demonstrate the capabilities of the new CESM configuration using mesoscale convective systems and tropical cyclones as exemplars.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.