Importance of aerosol composition and mixing state for cloud droplet activation over the Arctic pack ice in summer
Importance of aerosol composition and mixing state for cloud droplet activation over the Arctic pack ice in summer
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DOI：
10.5194/acp-15-2545-2015
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发表时间：
2015-01-01
影响因子：
6.3
通讯作者：
Svensson, E.
中科院分区：
文献类型：
--
作者：
Leck, C.;Svensson, E.
云凝结核（CCN）的浓度进行了测量，整个探险队的破冰船在北冰洋中部，包括3周的冰漂移业务在87度N，从2008年8月3日至9月9日。与该地区和该季节以前的观测结果一致，在0.2%的水蒸气过饱和度（SS）下，CCN的日平均浓度通常在15至30 cm（-3）的范围内，但浓度在整个考察期间变化了2至3个数量级，偶尔低于1 cm（-3）。CCN浓度最高的冰缘附近，并下降了3的因素，在第一个48小时的运输从公海到浮冰区。对于较长的运输时间，它们再次增加，表明在浮冰上的局部来源，建议是聚合物凝胶，通过气泡破裂在开放的引线上注入空气中的液滴。我们推断了无法解释的非水溶性气溶胶部分的性质，这是必要的复制所观察到的CCN浓度。这是可能的假设科勒理论和模拟云成核过程中使用拉格朗日绝热空气包裹模型，解决了动力学公式的水凝结的大小分辨气溶胶粒子。我们建议，内部/外部混合的水不溶性颗粒的部分是在相应的较小的气溶胶尺寸范围内较大。这些粒子在物理和化学上表现为聚合物凝胶：在云滴活化期间，聚合物凝胶结构上的亲水性和疏水性实体的相互作用最初仅显示出部分润湿特性和仅弱的吸湿性生长。给定时间，实现高CCN活化效率，这通过凝胶的亲水性或表面活性特性来促进。因此，在这项研究中的结果认为，高北极气溶胶的行为在CCN-计数器在水蒸汽SS> 0.4%（高相对湿度）的操作可能无法正确地解释传统的科勒理论。
Concentrations of cloud condensation nuclei (CCN) were measured throughout an expedition by icebreaker around the central Arctic Ocean, including a 3 week ice drift operation at 87 degrees N, from 3 August to 9 September 2008. In agreement with previous observations in the area and season, median daily CCN concentrations at 0.2% water vapour supersaturation (SS) were typically in the range of 15 to 30 cm(-3), but concentrations varied by 2 to 3 orders of magnitude over the expedition and were occasionally below 1 cm(-3). The CCN concentrations were highest near the ice edge and fell by a factor of 3 in the first 48 h of transport from the open sea into the pack ice region. For longer transport times they increased again, indicating a local source over the pack ice, suggested to be polymer gels, via drops injected into the air by bubbles bursting on open leads. We inferred the properties of the unexplained non-water soluble aerosol fraction that was necessary for reproducing the observed concentrations of CCN. This was made possible by assuming Kohler theory and simulating the cloud nucleation process using a Lagrangian adiabatic air parcel model that solves the kinetic formulation for condensation of water on size resolved aerosol particles. We propose that the portion of the internally/externally mixed water insoluble particles was larger in the corresponding smaller aerosol size ranges. These particles were physically and chemically behaving as polymer gels: the interaction of the hydrophilic and hydrophobic entities on the structures of polymer gels during cloud droplet activation would at first only show a partial wetting character and only weak hygroscopic growth. Given time, a high CCN activation efficiency is achieved, which is promoted by the hydrophilicity or surface-active properties of the gels. Thus the result in this study argues that the behaviour of the high Arctic aerosol in CCN-counters operating at water vapour SSs > 0.4% (high relative humidities) may not be properly explained by conventional Kohler theory.