Black carbon (BC) aerosol deposited in and onto Arctic snow increases the snow's absorption of sunlight and accelerates snowmelt. Wet removal of BC from the atmosphere plays a key role in determining its abundance in the Arctic atmosphere and in Arctic snow. However, this process is poorly understood, mainly due to the scarcity of relevant measurements. To study wet deposition of BC, we made measurements of mass concentration of BC in snow and rain (C_MBC) and of BC in air (M_BC) with high accuracy (16% and 10%, respectively) at the Barrow Atmospheric Baseline Observatory, Alaska, from July 2013 to August 2017 and analyzed them along with routinely measured meteorological parameters from Barrow. Monthly mean M_BC near the surface and C_MBC were poorly correlated from midwinter to early spring, when C_MBC was close to the annual median while M_BC was at its annual peak. Seasonal variations in the altitude distribution of M_BC may lead to these differences in seasonal variation of M_BC near the surface and C_MBC. About 50% of the annual wet deposition of BC occurred in the 3 months of summer, associated with high values of total precipitation and BC originating from biomass burning. Size distributions of BC in snow and rain were stable throughout the year, suggesting that the size distribution of BC in the lower troposphere was similarly stable. Calculations by two global models reproduced the observed seasonal variations of C_MBC and showed that BC from biomass burning dominated C_MBC in summer.

中文翻译：

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北极阿拉斯加黑碳湿沉降的季节性变化

沉积在北极雪中及其上的黑碳（BC）气溶胶会增加雪对阳光的吸收并加速融雪。从大气中湿去除BC在确定其在北极大气和北极雪中的丰度方面起着关键作用。但是，由于相关测量的稀缺性，人们对该过程的了解很少。为了研究BC的湿沉降，我们在巴罗大气基线观测站以高精度（分别为16％和10％）测量了雪和雨中BC（C _MBC）和空气中BC（M _BC）的质量浓度。于2013年7月至2017年8月在阿拉斯加提供服务，并对其进行了分析，并与常规测量的巴罗气象参数进行了比较。月平均M _BC从表层附近到C _MBC的相关性从冬至初春差，当C _MBC接近年中值而M _BC处于年峰值时。在的高度分布的季节性变化中号_BC可能导致的季节变化这些差异中号_BC的表面和近Ç _MBC。每年约有50％的BC湿沉降发生在夏季的3个月，这与高降水量和源自生物质燃烧的BC有关。全年在雨雪中的BC大小分布稳定，这表明对流层下部的BC大小分布稳定。由两个全球模型计算转载的观察季节变化Ç _MBC并表明，生物质燃烧BC为主Ç _MBC在夏季。