SnowPappus v1.0, a blowing-snow model for large-scale applications of the Crocus snow scheme

Full article: https://gmd.copernicus.org/articles/17/1297/2024/gmd-17-1297-2024.pdf

Led by Matthieu Baron

Abstract

Wind-induced snow transport has a strong influ- ence on snow spatial variability, especially at spatial scales between 1 and 500 m in alpine environments. Thus, the evo- lution of operational snow modelling systems towards 100– 500 m resolutions requires representing this process at these resolutions over large domains and entire snow seasons. We developed SnowPappus, a parsimonious blowing-snow model coupled to the state-of-the-art Crocus snow model able to cope with these requirements. SnowPappus simulates blowing-snow occurrence, horizontal transport flux and sub- limation rate at each grid cell as a function of 2D atmospheric forcing and snow surface properties. Then, it computes a mass balance using an upwind scheme to provide eroded or accumulated snow amounts to Crocus. Parameterizations used to represent the different processes are described in de- tail and discussed against existing literature. A point-scale evaluation of blowing-snow fluxes was conducted, mainly at the Col du Lac Blanc observatory in the French Alps. Eval- uations showed that SnowPappus performs as well as the currently operational scheme SYTRON in terms of blowing- snow occurrence detection, while the latter does not give ac- cess to spatialized information. Evaluation of the simulated suspension fluxes highlighted a strong sensitivity to the sus- pended particle’s terminal fall speed. Proper calibrations al- low the model to reproduce the correct order of magnitude of the mass flux in the suspension layer. Numerical per- formances of gridded simulations of Crocus coupled with SnowPappus were assessed, showing the feasibility of us- ing it for operational snow forecast at the scale of the entire French Alps.