Reduction of snow albedo from vehicle emissions at Portillo, Chile

Only scarce literature exists on the effect of direct deposition of vehicle particulate matter emissions onto snow surfaces with well-quantified sources and atmospheric conditions. Local emissions from vehicles in the surroundings of ski resorts not only reduce the whiteness of the snowy landscape affecting the attractiveness to visitors, but also modify the onset of snowmelt and thus the environmental equilibrium of the local area and of the surrounding region. The changes in albedo observed at Portillo, in the Chilean Andes, were an increase of around 0.17 units after a heavy snowfall (20 cm accumulation), an increase of around 0.07 after a prolonged lighter snowfall (10 cm accumulation), and a mean decrease of around 0.08 units per day with heavy traffic (around 2000 vehicles per day). Other parameters such as wind velocity and direction did not greatly affect the snow albedo during this study because the wind direction was fairly constant due to the terrain restriction. It is difficult to estimate how much the snow metamorphism and melting contributed to the observed decrease. The albedo changes observed are helpful to confirm the close cause-effect relationship between these parameters and the snow albedo, and to foresee that traffic restriction may allow for more stable snowpack conditions. The case study presented here can be extrapolated to other vehicle-contaminated snow areas, thus examining their contribution to snow radiative forcing and climate change at multiple scale.