WRF-Chem-Polar: an open, collaborative, and reproducible framework for modeling the polar atmosphere

Over the past 15 years, substantial developments have been made to adapt the regional chemistry-climate model WRF-Chem for applications in polar environments, with a main focus on the Arctic. These developments address key processes that are either absent from, or insufficiently represented in, the standard WRF-Chem distribution, particularly those controlling aerosol-cloud interactions, boundary layer chemistry, and surface-atmosphere coupling over snow, sea ice, and the polar ocean. However, until now, these advances have been distributed across multiple publications, code branches, and project-specific implementations, limiting transparency, reproducibility, and community use.

Here we present WRF-Chem-Polar, a consolidated and openly available modeling framework that integrates our polar-specific model developments into a single, traceable code base. The framework is hosted on GitHub and is structured around two tightly linked components: (i) a unified WRF-Chem-Polar model code that incorporates developments for polar aerosol and cloud processes and (ii) a dedicated infrastructure for compiling, running, and analyzing simulations.

A key objective of WRF-Chem-Polar (including the model code and infrastructure) is to enable transparent model evolution. All developments are tracked through version control, with automated test cases designed to systematically compare model behavior across code versions. This approach allows scientific changes to be evaluated quantitatively, supports regression testing, and facilitates controlled experimentation when introducing new parameterizations or process representations. The infrastructure also provides transparent workflows for simulation setup, post-processing, and diagnostics, improving reproducibility across users and platforms. Code quality, readability, and consistency is improved via coding style guides and modern software tools that include unit testing and automatic enforcement of linting rules.

By making these developments openly accessible and actively maintained, WRF-Chem-Polar lowers the barrier for the community to apply advanced polar chemistry–aerosol–cloud representations, while providing a robust framework for continued development and evaluation. This effort supports both fundamental process studies and applied research and contributes to broader open-science and FAIR modeling and furthers our objective of uptake of our work within the Earth system modeling community.