Impact of nucleation on global CCN
Impact of nucleation on global CCN
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DOI：
10.5194/acp-9-8601-2009
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发表时间：
2009-01-01
影响因子：
6.3
通讯作者：
Carslaw, K. S.
中科院分区：
文献类型：
--
作者：
Merikanto, J.;Spracklen, D. V.;Carslaw, K. S.
云凝结核（CCN）来自直接排放到大气中的粒子（一次排放）或来自大气中成核的纳米级粒子的生长。将这两种来源分开是很重要的，因为它们对气体和颗粒物排放控制策略以及环境变化的反应方式不同。在这里，我们使用一个全球气溶胶微物理模型来量化的主要和有核粒子的全球CCN的贡献。该模型认为，主要排放的海喷雾，硫酸盐和碳质颗粒，和成核过程适合于自由对流层和边界层。我们估计，在0.2%过饱和度下，全球低空云云凝结核中有45%是来自成核的二次气溶胶（考虑到一次排放和成核率的不确定性，范围在31-49%之间），其余来自一次排放。该模型表明，全球低层云中35%的CCN（0.2%）是在自由对流层和对流层上层形成的。在海洋边界层中，55%的云凝结核（0.2%）来自成核，45%来自自由对流层，10%直接在边界层中成核。模型运行的组合表明，主要和成核CCN是非线性耦合。特别是，边界层成核的CCN强烈抑制在自由对流层中成核的粒子的初级排放和夹带。消除所有一次排放仅使全球CCN（0.2%）减少20%，消除对流层上部成核仅使CCN（0.2%）减少12%，因为边界层成核的贡献增加。
Cloud condensation nuclei (CCN) are derived from particles emitted directly into the atmosphere (primary emissions) or from the growth of nanometer-sized particles nucleated in the atmosphere. It is important to separate these two sources because they respond in different ways to gas and particle emission control strategies and environmental changes. Here, we use a global aerosol microphysics model to quantify the contribution of primary and nucleated particles to global CCN. The model considers primary emissions of sea spray, sulfate and carbonaceous particles, and nucleation processes appropriate for the free troposphere and boundary layer. We estimate that 45% of global low-level cloud CCN at 0.2% supersaturation are secondary aerosol derived from nucleation (ranging between 31-49% taking into account uncertainties in primary emissions and nucleation rates), with the remainder from primary emissions. The model suggests that 35% of CCN (0.2%) in global low-level clouds were created in the free and upper troposphere. In the marine boundary layer 55% of CCN (0.2%) are from nucleation, with 45% entrained from the free troposphere and 10% nucleated directly in the boundary layer. Combinations of model runs show that primary and nucleated CCN are non-linearly coupled. In particular, boundary layer nucleated CCN are strongly suppressed by both primary emissions and entrainment of particles nucleated in the free troposphere. Elimination of all primary emissions reduces global CCN (0.2%) by only 20% and elimination of upper tropospheric nucleation reduces CCN (0.2%) by only 12% because of the increased contribution from boundary layer nucleation.