High resolution modelling of dust and black carbon deposition events on snow in the Alps.

The environment in alpine regions is impacted by transported anthropogenic pollutants and mineral dust. Upon deposition, both dust and black carbon act as light absorbing particles (LAP) with potential impacts on albedo and the rate of melting for alpine snowpacks. In April/May 2018 a strong dust deposition event was observed within the seasonal snowpack at the Lautaret pass in the French Alps. This comes in addition to the background BC deposition that occurred during the same period. Here, we use the regional Weather Research and Forecasting model with Chemistry (WRF-Chem) to simulate the sources, processing, and deposition of both dust and black carbon (BC) to the alpine snowpack during this period. Our goal is to accurately simulate the full lifecycle of dust and BC from initialemissions, transport and processing in the atmosphere, and removal via wet and dry deposition. We use the model with three nested domains including the primary dust emissions region in Africa (low resolution domain), a second domain the includes Europe, and a third high resolution domain over the Alps. The goal of using this setup is to describe meteorology at different scales, including long range transport of dust as well as high resolution meteorology over the complex alpine terrain within the Alps, as they impact aerosol deposition. The meteorological variables estimates are evaluated against in situ measurement at the Lautaret pass. We also evaluate the ability of the model to accurately simulate the transport and deposition of the Saharan dust and black carbon that was observed within snow. Future plans include using model predicted dust and BC deposition rates to drive a physically based snowpack model for this same period to evaluate their impact on snowpack evolution.