Regional Impact of Snow‐Darkening on Snow Pack and the Atmosphere During a Severe Saharan Dust Deposition Event in Eurasia.

Light‐absorbing impurities such as mineral dust can play a major role in reducing the albedo of snow surfaces. Particularly in spring, deposited dust particles lead to increased snow melt and trigger further feedbacks at the land surface and in the atmosphere. Quantifying the extent of dust‐induced variations is difficult due to high variability in the spatial distribution of mineral dust and snow. We present an extension of a fully coupled atmospheric and land surface model system to address the impact of mineral dust on the snow albedo across Eurasia. We evaluated the short‐term effects of Saharan dust in a case study. To obtain robust results, we performed an ensemble simulation followed by statistical analysis. Mountainous regions showed a strong impact of dust deposition on snow depth. We found a mean significant reduction of −1.4 cm in the Caucasus Mountains after 1 week. However, areas with flat terrain near the snow line also showed strong effects despite lower dust concentrations. Here, the feedback to dust deposition was more pronounced as increase in surface temperature and air temperature. In the region surrounding the snow line, we found an average significant surface warming of 0.9 K after 1 week. This study shows that the impact of mineral dust deposition depends on several factors. Primarily, these are altitude, slope, snow depth, and snow cover fraction. Especially in complex terrain, it is therefore necessary to use fully coupled models to investigate the effects of mineral dust on snow pack and the atmosphere. Plain Language Summary: Dust particles such as Saharan dust can darken snow surfaces, leading to increased absorption of solar radiation. The result is earlier snow melt in the spring and a warming of the land surface. Predicting dust deposition and subsequent regional impacts is difficult because the distribution of snow and dust appears in complex patterns depending on the landscape. We extended an atmospheric and land surface model system to investigate the impact of Saharan dust particles across Eurasia during a Saharan dust transport event. We found that mountainous regions are particularly affected by the dust particles, leading to increased snowmelt. In addition, regions with thin and patchy snow cover show a strong response to the dust particles, mainly causing a warming of the land surface. We found that the effects of dust particles depend on different regional characteristics. Therefore, when investigating dust on snow, it is important to use model systems that represent both the atmospheric process and surface properties properly. Key Points: There are regional effects due to the high spatial variability in mineral dust and snow propertiesThin snow layers favor a rise in temperature, higher elevations mainly show accelerated snow meltWe found a significant impact on surface radiation, temperature and snow cover properties [ABSTRACT FROM AUTHOR]