Modeling the impact of air pollution deposition on the alpine snow lifecycle

Foteini Baladima

Modeling snow cover in mountain regions is a major research challenge that links air pollution, weather, water, and climate. Currently, a major limitation of understanding the alpine seasonal snow pack is poor knowledge of how light absorbing particles (LAP) impact snow albedo and snow cover evolution. One limitation for predicting the impact of these LAP is lack of knowledge of what and how light absorbing impurities (mainly dust and black carbon aerosols) get deposited from the atmosphere to the snowpack. In this thesis we use a high resolution (up to 1 km x 1 km resolution) regional chemical transport model, WRF-Chem, to predict the full atmospheric lifecycle of aerosols from initial emissions through the atmosphere (transport and processing) to predict the rate of removal through deposition. Anthropogenic emissions of back carbon aerosols and natural dust emissions sources (e.g. Saharan dust) will be included. The limited area model will use initial and boundary conditions from a global model in order to capture long range hemispheric transport of dust and black carbon aerosols. We use the fully coupled version of WRF-Chem that predicts online the impacts of aerosols on clouds and the meteorological cycle (i.e. rain and snowfall) to accurately describe aerosol removal rates and deposition. Model predicted deposition rates will be compared with measurements at alpine stations (Col de Porte and/or Col du Lautaret) within the context of the EBONI (dEposition, BecOmiNg and impact of light absorbing Impurities in snow) ANR project and other ongoing measurements made by Centre Etude de la Neige (CEN) and IGE. The model predicted deposition rates will then be used to force the snowpack model CROCUS to predict the impact of these impurities on snowpack physics, including snow albedo and snow metamorphism processes. These results will be compared with measured snowpack properties in alpine environments to evaluate model performance and suggest uncertainties in atmospheric inputs and/or snowpack physics that should be addressed in future work. The results will also be compared to existing atmospheric models (ALADIN and MOCAGE) of deposition fluxes, in order to quantify the benefit of using a high resolution regional chemical transport model.

Supervisors  : J. THOMAS (CHIANTI) and D. VOISIN (CHIANTI)