Expansion of the UFS Hierarchical System Development (HSD) Framework: New Aquaplanet Case Added to the UFS-Weather Model

[priyarpillai]

The NOAA Earth Prediction Innovation Center (EPIC) is pleased to announce the development and integration of an idealized Aquaplanet test case into the Unified Forecast System Weather Model (UFS-WM) Hierarchical System Development (HSD) framework. This capability, added in February 2026, was developed in collaboration with NOAA's Physical Sciences Laboratory (PSL).

EPIC and PSL's goal was to create a comparable test for the UFS-WM that enables the broader Earth system modeling community to conduct meteorological research using an easy-to-deploy model configuration and workflow. In this test case configuration, we used a coarse ~ 2° × 2° grid (C48 resolution). Historically, Aquaplanet idealized tests have been widely used to study ocean-atmosphere interactions by simplifying the complex feedbacks present in a fully-coupled Earth System Model (ESM). This simplification restricts interactions to ocean-atmosphere components by removing land, sea ice, and other processes. This reduction in complexity enables researchers to isolate key physical mechanisms and discern more robust insights into the impact of their scientific and code innovations on forecast skill and model performance.

The idealized Aquaplanet test case is now available in the develop branch of the UFS-WM. Required input data, fix files, and model configuration files are pre-staged on all NOAA Tier 1 platforms. Users can also run the test case using the Intel runtime environment container. The container and all necessary data for the Aquaplanet case are available via the HSD S3 bucket. Additionally, a user-friendly plotting script is included in the tests-dev directory of the UFS-WM codebase.

The HSD section of the UFS-WM User's Guide has been updated to reflect these enhancements and to help users configure and run the Aquaplanet case. Interested users can get additional support by submitting questions through the UFS-WM GitHub Discussions Q & A page.

For more information about this release, including contributors, see the related article on the EPIC website!