A New Ice Nucleation Active Site Parameterization for Desert Dust and Soot
A New Ice Nucleation Active Site Parameterization for Desert Dust and Soot
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DOI：
10.1175/jas-d-16-0074.1
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发表时间：
2017-03-01
影响因子：
3.1
通讯作者：
Leisner, Thomas
中科院分区：
文献类型：
--
作者：
Ullrich, Romy;Hoose, Corinna;Leisner, Thomas
基于德国卡尔斯鲁厄大气气溶胶相互作用和动力学(AIDA)小室11年的非均质冰成核实验结果，发展了一个新的非均质冰成核经验参数化框架。该框架目前包括沙漠沙尘和烟尘气溶胶，并通过冰核活动表面位置(INAS)的方法来量化冰核形成效率。所有沙漠沙尘实验的浸没冻结INAS密度n(S)遵循作为温度的函数的指数拟合，与AIDA实验的早期分析很好地一致。沙漠沙尘的沉积成核n(S)等值线在240K以下的冰饱和比-温度(Si-T)图上呈U型曲线，这些等值线的负斜率可以用经典成核理论解释，而向更高温度的行为可能是由孔隙凝结和冻结机制引起的。在低于240K的温度下测得的碳烟的沉积成核也遵循U形等值线，对于有机碳含量较高的碳烟，其沉积成核曲线向更高的硅方向移动。对于烟尘气溶胶的浸没冻结，只确定了n的上限(S)，并用它重新定标了现有的参数化线。将新的参数化框架与基于碳纳米管的参数化框架和模式中使用的经验框架进行了比较。对比表明，S等值线在形状和大小上存在较大差异，尤其是沉积成核。对于模型中的应用，这种新框架的实现比其他表达式的实现更简单。
Based on results of 11 yr of heterogeneous ice nucleation experiments at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) chamber in Karlsruhe, Germany, a new empirical parameterization framework for heterogeneous ice nucleation was developed. The framework currently includes desert dust and soot aerosol and quantifies the ice nucleation efficiency in terms of the ice nucleation active surface site (INAS) approach.The immersion freezing INAS densities n(S) of all desert dust experiments follow an exponential fit as a function of temperature, well in agreement with an earlier analysis of AIDA experiments. The deposition nucleation n(S) isolines for desert dust follow u-shaped curves in the ice saturation ratio-temperature (Si-T) diagram at temperatures below about 240 K. The negative slope of these isolines toward lower temperatures may be explained by classical nucleation theory (CNT), whereas the behavior toward higher temperatures may be caused by a pore condensation and freezing mechanism. The deposition nucleation measured for soot at temperatures below about 240K also follows u-shaped isolines with a shift toward higher Si for soot with higher organic carbon content. For immersion freezing of soot aerosol, only upper limits for n(S) were determined and used to rescale an existing parameterization line.The new parameterization framework is compared to a CNT-based parameterization and an empirical framework as used in models. The comparison shows large differences in shape and magnitude of the n(S) isolines especially for deposition nucleation. For the application in models, implementation of this new framework is simple compared to that of other expressions.