2026-08-12 –, Room 3
The snow cover plays a central role in many Earth system processes, for example influencing climate feed-back, the hydrological cycle, as well as glacier and ice sheet mass balance. Widely used snow cover models such as SNOWPACK (C++) and Crocus (Fortran) show strong performance in operational forecasting and scientific modeling. However, their still tightly entangled code bases make it difficult for the community to modify model components efficiently. This is due to technical dept as well as limitations of the programming languages itself. Recent advances in snow physics parameterizations have highlighted structural limitations in those models, underscoring the need for a more flexible modelling framework.
To address these challenges, we present Helmut, a modular snow cover model implemented in Julia. Helmut combines a state‑of‑the‑art snow process equation solver within a design that emphasizes flexibility, and quick experimentation. Julia’s multiple dispatch allows Helmut users to extend or replace individual components—such as parameterizations, boundary‑conditions, or physical process formulations - efficiently. This enables domain scientists to contribute easily and test new advances with minimal friction.
Helmut successfully reproduces simulations from existing snow models while offering a much more accessible framework for modifying model physics, testing new parameterizations, and experimenting with alternative numerical formulations. We further demonstrate how the structure enables exploration of the impacts of different parameterizations and physical configurations, making such investigations considerably easier.
Helmut was developed in collaboration between the Snow Studies Centre in Grenoble, France, the developers of Crocus and the WSL Institute for Snow and Avalanche research SLF in Davos, Switzerland, the developers of SNOWPACK. It therefore benefited from the combined knowledge, with the goal of having a unified snow model that can be adjusted as needed. Such adjustments can be as simple as introducing a new type of material layer, for example glacier ice, or a new parameterziation for thermal conductivity, to as complex as a new physics-based process that needs to be solved in a coupled fashion with other processes. As of now, most parametrizations for snow follow the Crocus model, while the integrated soil model closely follows the implementation in SNOWPACK. The goal is to have parametrizations that are like SNOWPACK’s and Crocus’s in the model and as a starting point for community-driven future model developments. In this contribution, we show the general model structure and show examples of how the flexible model structure can be leveraged to explore different physics configurations and add new parametrizations. One of these examples demonstrate how soil layers can be defined as extension of the general layer type, and the inclusion of a new detailed radiative transfer process by implementing the Tartes model for albedo.
Background in physics and complex systems, transitioned to scientific software engineering at the Institute for Snow and Avalanches.