Scientists from the Institut des Géosciences de l’Environnement of Grenoble, the Centre d’Etudes de la Neige and the Groupe de Météorologie Expérimentale et Instrumentale have developed a new approach for measuring the interaction between snow and sunlight. This methodology is important to improve the accuracy of climate models. They did X-ray tomography experiments at ESRF ID19 beamline. The results are published in Nature Communications.
Once deposited on the ground, snow is a material composed of air and ice crystals, whose shape and arrangement vary greatly at the micrometre scale. This is known as the microstructure of snow. This “skeleton” of ice and air governs the propagation of light within the snowpack through optical phenomena such as refraction and internal reflections in the ice phase.
However, despite its extreme complexity and irregularity, natural snow is still represented in a simplistic manner in almost all optical models, including those implemented in climate models. These models typically depict snow as a collection of ice particles with perfect geometric shapes, mainly spheres. Among the many implications for the energy balance of snow, this simplification leads to significant uncertainties in climate modelling, with potential impacts of up to 1.2°C on global air temperature.
In this new study, the authors from the Institut des Géosciences de l’Environnement of Grenoble (IGE / CNRS – INRAE – IRD – UGA – Grenoble INP-UGA), the Centre d’Etudes de la Neige (CEN / CNRM / Météo-France – CNRS) and the Groupe de Météorologie Expérimentale et Instrumentale (GMEI / CNRM / Météo-France – CNRS) have accurately simulated the light propagation in a collection of 3D images of snow microstructure obtained by X-ray tomography, using a ray-tracing model. Very different snow types were investigated, from fresh snow (PP) to refrozen melt-freeze forms (MF). Some images were obtained at the 3SR-Lab. Several snow microstructures required higher resolution and were acquired at ESRF beamline ID19.
Read more on the ESRF website
Image: Snow microstructure: This is what fresh snow looks like at the micrometre scale