Measurements of light-absorbing impurities in snow over four glaciers on the Tibetan Plateau
Measurements of light-absorbing impurities in snow over four glaciers on the Tibetan Plateau
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DOI：
10.1016/j.atmosres.2020.105002
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发表时间：
2020-10
影响因子：
5.5
通讯作者：
H. Niu;Shi-chang Kang;Yuhang Wang;C. Sarangi;D. Rupakheti;Y. Qian
中科院分区：
文献类型：
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作者：
H. Niu;Shi-chang Kang;Yuhang Wang;C. Sarangi;D. Rupakheti;Y. Qian
黑碳（BC）、灰尘和有机碳（OC）气溶胶沉积在冰川表面时，可以吸收光线，减少降雪量。雪中的这些杂质被称为ILAI（即，不溶性光吸收杂质）。大气化学模式已被广泛用于模拟冰川地区大气气溶胶的输送和沉积。然而，在青藏高原（TP）的冰川积雪的ILAIs的系统调查是罕见的。在这项研究中，ILAIs在雪中的观测和大气气溶胶的ILAIs在地面上的四个冰川上的TP的模拟进行了分析。在地表老化雪中，BC和灰尘之间存在较强的相关性，并且它们的相关性随雪坑深度而显著变化。雪坑中的BC和OC浓度随深度的增加而降低。ILAI浓度在不同深度区间的显著差异反映了ILAI在雪坑中不同的物理化学性质和沉积后过程，为相关过程提供了重要的观测约束。冰川上空近地面大气ILAI的月变化具有明显的空间异质性。统计结果表明，2015年夏季ILAI浓度高于2014年，这与CALIPSO观测结果定性一致，可能反映了夏季风年际变化对积雪ILAI负荷的影响。随着雪坑深度的增加，BC的光衰减（ATN）逐渐减小，而BC的质量吸收截面（MAC）在整个雪坑剖面上的变化趋势与ATN相反。扫描电子显微镜（SEM）成像表明，富含钙和硅的颗粒占主导地位的生物，石英和飞灰颗粒的cryoconite，提供额外的限制雪中尘的来源，可以促进更好地了解的物理化学性质和气候效应的颗粒在冰川cryoconite。
Black carbon (BC), dust, and organic carbon (OC) aerosols, when deposited onto the surface of glaciers, can absorb light and decrease the snow albedo. These impurities in snow are referred to as ILAIs (i.e., insoluble light absorbing impurities). Atmospheric chemical models have been extensively used to simulate the transport and deposition of atmospheric aerosols in glacierized areas. However, systematic investigations of ILAIs in snowpack of glaciers on the Tibetan Plateau (TP) are rare. In this study, observations of ILAIs in snow and simulations of ILAIs of atmospheric aerosol at surface over four glaciers on the TP have been analyzed. Strong correlation between BC and dust was found in surface aged-snow, and their correlation significantly varied with snowpit depth. BC and OC concentrations in snowpit tended to decrease with depth. Significant differences of ILAI concentrations among depth intervals reflect their diverse hydrophilicities, physiochemical properties and post-depositional processes in snowpit, offering important observational constraints on the related processes. Monthly variation of atmospheric ILAIs at surface over glaciers is characterized by distinct spatial heterogeneity. The statistical results show higher ILAI concentrations in the summer of 2015 than 2014, which is in qualitative agreement with CALIPSO observations, likely reflecting the effects of inter-annual variation of summer monsoon on snow ILAI loadings. Optical attenuation (ATN) of BC is gradually decreased with depth of snowpit, whereas the trend of mass absorption cross-section (MAC) of BC throughout the profile of snowpit is opposite to that of ATN. The scanning electron microscopy (SEM) imaging demonstrates that calcium and silicon rich particles dominate over biological, quartz and flying ash particles in the cryoconite, providing additional constraints on the sources of dust-in-snow and can facilitate better understanding of the physicochemical properties and climatic effects of particles in the glacial cryoconite.