Regional Impact of Snow-Darkening During a Severe Saharan Dust Deposition Event in 2018 Across Eurasia

Abstract

Aerosols such as mineral dust particles reduce the surface albedo when deposited on snow. This leads to increased absorption of solar radiation. Especially in spring, this phenomenon can lead to increased snowmelt, which triggers further feedbacks at the land surface and in the atmosphere. Quantifying the magnitude of dust-induced variations is difficult because of the 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 investigate the effects of mineral dust on snow albedo across Eurasia. In a comprehensive ensemble simulation study, we investigated the short-term effects of an extreme Saharan dust deposition event in 2018. We found region-dependent feedbacks. Mountainous regions and areas near the snowline showed a strong impact from mineral dust deposition. The former showed a particularly strong decrease in snow depth. For instance, in the Caucasus Mountains we found a mean significant decrease in snow depth of -1.4 cm after one week. The latter showed a stronger feedback effect on surface temperature. In the flat region around the snow line, we found a mean significant surface warming of 0.9 K after one week. This study shows that the effects of mineral dust deposition depend on several factors. Primarily, these are elevation, slope, snow depth, and fraction of snow cover. Therefore, especially in complex terrain, it is necessary to use fully coupled models to study the effects of mineral dust on the snowpack and the atmosphere.