An AeroCom assessment of black carbon in Arctic snow and sea ice
An AeroCom assessment of black carbon in Arctic snow and sea ice
复制标题
DOI：
10.5194/acp-14-2399-2014
复制
发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Zhang, K.
中科院分区：
文献类型：
--
作者：
Jiao, C.;Flanner, M. G.;Zhang, K.
虽然许多全球气溶胶模式预测了地表沉积，但只有少数模式被用来直接模拟黑碳（BC）沉积对雪和海冰的辐射效应。本文利用AeroCom项目两个阶段中25个模式的气溶胶沉积场来模拟和评估北极雪内BC浓度和辐射效应。我们通过在2004 - 2009年不同沉积场和气象条件下驱动社区地球系统模型的离线陆地和海冰组分来实现这一目标，在此期间，在北极积雪中进行了广泛的BC测量。我们发现，模型通常低估了俄罗斯北部和挪威雪中的BC浓度，而高估了北极其他地方的BC含量。虽然模拟的BC在雪中的分布与测量值相关性较差，但平均值是合理的。与观测平均值19.2 ng g（-1）相比，在相同网格单元、雪深和测量月份上采样的BC浓度的多模型平均（范围）偏差在AeroCom模型的早期阶段（第一阶段）为-4.4(-13.2至+ 10.7)ng g(-1)，在AeroCom模型的较新阶段（第二阶段）为+ 4.1(-13.0至+ 21.4)ng g（-1）。决定北极雪中模式BC浓度的因素包括北极BC排放、北极外气溶胶的运输、降水、北极内气溶胶的沉积效率以及融水对雪中颗粒的去除。敏感性研究表明，模型测量评价受融水清除效率的影响较弱，因为大多数测量是在未融化的积雪中进行的。在第二阶段模式中，北极（60-90°N）大气中BC的停留时间为3.7 ~ 23.2天，这意味着当地BC沉积效率在模式间存在较大差异。结合大多数北极BC沉积来自北极外排放的事实，这些结果表明，气溶胶去除过程是模式性能变化的主要来源。在第一阶段和第二阶段模式下，BC在雪中的北极辐射效应的多模式平均值（全范围）分别为0.15 (0.07-0.25)wm（-2）和0.18 (0.06-0.28)wm（-2）。在校正了与北极不同地区观测到的BC浓度相关的模式偏差后，我们得到了联合AeroCom集合的多模式平均北极辐射效应为0.17W m（-2）。最后，在观测地点取样的模拟BC浓度与整个北极之间存在高度相关性，这表明野外活动提供了一个合理的北极样本。
Though many global aerosols models prognose surface deposition, only a few models have been used to directly simulate the radiative effect from black carbon (BC) deposition to snow and sea ice. Here, we apply aerosol deposition fields from 25 models contributing to two phases of the Aerosol Comparisons between Observations and Models (AeroCom) project to simulate and evaluate within-snow BC concentrations and radiative effect in the Arctic. We accomplish this by driving the offline land and sea ice components of the Community Earth System Model with different deposition fields and meteorological conditions from 2004 to 2009, during which an extensive field campaign of BC measurements in Arctic snow occurred. We find that models generally underestimate BC concentrations in snow in northern Russia and Norway, while overestimating BC amounts elsewhere in the Arctic. Although simulated BC distributions in snow are poorly correlated with measurements, mean values are reasonable. The multi-model mean (range) bias in BC concentrations, sampled over the same grid cells, snow depths, and months of measurements, are -4.4 (-13.2 to + 10.7) ng g(-1) for an earlier phase of AeroCom models (phase I), and + 4.1 (-13.0 to + 21.4) ng g(-1) for a more recent phase of AeroCom models (phase II), compared to the observational mean of 19.2 ng g(-1). Factors determining model BC concentrations in Arctic snow include Arctic BC emissions, transport of extra-Arctic aerosols, precipitation, deposition efficiency of aerosols within the Arctic, and meltwater removal of particles in snow. Sensitivity studies show that the model-measurement evaluation is only weakly affected by meltwater scavenging efficiency because most measurements were conducted in non-melting snow. The Arctic (60-90 degrees N) atmospheric residence time for BC in phase II models ranges from 3.7 to 23.2 days, implying large inter-model variation in local BC deposition efficiency. Combined with the fact that most Arctic BC deposition originates from extra-Arctic emissions, these results suggest that aerosol removal processes are a leading source of variation in model performance. The multi-model mean (full range) of Arctic radiative effect from BC in snow is 0.15 (0.07-0.25) W m(-2) and 0.18 (0.06-0.28) W m(-2) in phase I and phase II models, respectively. After correcting for model biases relative to observed BC concentrations in different regions of the Arctic, we obtain a multi-model mean Arctic radiative effect of 0.17W m(-2) for the combined AeroCom ensembles. Finally, there is a high correlation between modeled BC concentrations sampled over the observational sites and the Arctic as a whole, indicating that the field campaign provided a reasonable sample of the Arctic.