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  • 1
    Publication Date: 2024-03-05
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉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.〈/p〉
    Description: 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.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉There are regional effects due to the high spatial variability in mineral dust and snow properties〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Thin snow layers favor a rise in temperature, higher elevations mainly show accelerated snow melt〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉We found a significant impact on surface radiation, temperature and snow cover properties〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Initiative and Networking Fund of the Helmholtz Association
    Description: https://doi.org/10.35097/1579
    Keywords: ddc:551.5 ; light‐absorbing impurities ; dust on snow ; snow albedo ; regional impact ; modeling ; ensemble simulation
    Language: English
    Type: doc-type:article
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  • 2
    Publication Date: 2022-03-14
    Description: The size and shape of snow grains directly impacts the reflection by a snowpack. In this article, different approaches to retrieve the optical-equivalent snow grain size (ropt) or, alternatively, the specific surface area (SSA) using satellite, airborne, and ground-based observations are compared and used to evaluate ICON-ART (ICOsahedral Nonhydrostatic—Aerosols and Reactive Trace gases) simulations. The retrieval methods are based on optical measurements and rely on the ropt-dependent absorption of solar radiation in snow. The measurement data were taken during a three-week campaign that was conducted in the North of Greenland in March/April 2018, such that the retrieval methods and radiation measurements are affected by enhanced uncertainties under these low-Sun conditions. An adjusted airborne retrieval method is applied which uses the albedo at 1700 nm wavelength and combines an atmospheric and snow radiative transfer model to account for the direct-to-global fraction of the solar radiation incident on the snow. From this approach, we achieved a significantly improved uncertainty (〈25%) and a reduced effect of atmospheric masking compared to the previous method. Ground-based in situ measurements indicated an increase of ropt of 15 μm within a five-day period after a snowfall event which is small compared to previous observations under similar temperature regimes. ICON-ART captured the observed change of ropt during snowfall events, but systematically overestimated the subsequent snow grain growth by about 100%. Adjusting the growth rate factor to 0.012 μm2 s�1 minimized the difference between model and observations. Satellite-based and airborne retrieval methods showed higher ropt over sea ice (〈300 μm) than over land surfaces (〈100 μm) which was reduced by data filtering of surface roughness features. Moderate- Resolution Imaging Spectroradiometer (MODIS) retrievals revealed a large spread within a series of subsequent individual overpasses, indicating their limitations in observing the snow grain size evolution in early spring conditions with low Sun.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
    Publication Date: 2022-02-18
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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