Orange snow and citizen science

<p>In the beginning of February 2021, a large dust plume travelled from the Sahara across the Mediterranean Sea and deposited a colorful layer of particles on the snow-covered slopes of the&#160;Pyrenees and the Alps. The event was widely reported in the media due to the surprising color of the sky and of the snow cover.<span>&#160;</span></p><p>To characterize the amount of dust deposited on the ground during this remarkable event, we organized a citizen science campaign. We collected 150 snow samples from which the deposited dust mass was measured over the Pyrenees, the French and the Swiss Alps. The analysis of all samples shows a robust deposition gradient from the Pyrenees to the Alps and enhanced deposition rates on south facing slopes in agreement with satellite data. The samples were used in combination with detailed snow modeling to evaluate the dramatic impact of the dust deposition on the melt and duration of the snow cover.<span>&#160;</span></p>