Homogeneous ice nucleation in aqueous ammonium sulfate aerosol particles
Homogeneous ice nucleation in aqueous ammonium sulfate aerosol particles
复制标题
硫酸铵水溶液气溶胶颗粒中的均匀冰核形成
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
S. Martin
中科院分区：
文献类型：
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作者：
J. H. Chelf;S. Martin
云的形成机制影响云的辐射特性。因此，准确的云形成模式和相关的全球变暖模式需要硫酸铵颗粒的冻结数据，硫酸铵颗粒是对流层上层云的主要成分。几个实验室小组研究了水硫酸铵颗粒中的均匀冰核；然而，在报告的数据中存在重大分歧。在目前的工作中，冰的冻结温度是通过将由蒸汽冷凝产生的（nh4） 2 so4颗粒通过温度控制的流动池来测量的，在流动池中，用红外光谱检测冰的形成。为了确定几个实验室之间不同结果的可能解释，本研究中使用的实验方法被仔细检查。进行实验以排除伪影，并改变实验条件以发展对颗粒冻结过程的完整理解。所有的实验都产生一致的结果。目前研究中采用的气溶胶流管技术的传质计算表明，10.4到10.6中的一个冷冻颗粒可以从周围过冷的水颗粒中清除足够的水蒸气，使得单个冰粒积累足够的质量，从而在红外光谱中产生正冻结事件。这一结果似乎部分解释了几个实验室采用不同实验方法观察硫酸铵中均匀冰核的混乱和相互矛盾的结果。6下限J(1厘米3 s)值确定为1.1 - 1 x 10 6(233±1 K, x = 0.013±0.001),1.1×10 6(231±1 K, x = 0.029±0.004),1.7×10 6(227±1 K, x = 0.066±0.015),2.8×10 6(226±1 K, x = 0.071±0.018),8.4×10 6(224±1 K, x = 0.097±0.034),和8.4 x 10 8(221±1 K, x = 0.153±0.076),在相关的温度和溶质摩尔分数水成分(x)在括号指出。
The mechanisms involved in cloud formation affect the resulting cloud radiative properties. Therefore, accurate cloud formation models and related global warming models require freezing data for ammonium sulfate particles, a major constituent of upper tropospheric clouds. Homogeneous ice nucleation in aqueous ammonium sulfate particles has been studied by several laboratory groups; however, there is significant disagreement in the reported data. In the present work, the ice freezing temperatures are measured by sending (NH 4 ) 2 SO 4 particles, generated by vapor condensation, through a temperature-controlled flow cell, where ice formation is detected with infrared spectroscopy. To determine possible explanations for disparate results among several laboratories, the experimental methods used in this study are closely examined. Experiments are performed to preclude artifacts, and experimental conditions are varied to develop a complete understanding of processes involved in particle freezing. All experiments produce consistent results. Mass transfer calculations for the aerosol flow tube technique employed in the current study suggest that one frozen particle in 10 4 to 10 6 may scavenge sufficient water vapor from surrounding supercooled aqueous particles such that a single ice particle accumulates enough mass to yield a positive freezing event in the infrared spectrum. This result appears to partially explain the confusing and conflicting results coming from several laboratories employing different experimental methods to observe homogeneous ice nucleation in ammonium sulfate. Six lower limit J (cm -3 s -1 ) values are determined as 1.1 1 x 10 6 (233 ± 1 K, x=0.013±0.001), 1.1 × 10 6 (231 ± 1 K, x=0.029±0.004), 1.7 × 10 6 (227±1 K, x=0.066±0.015), 2.8 × 10 6 (226±1 K, x=0.071±0.018), 8.4 × 10 6 (224±1 K, x=0.097 ±0.034), and 8.4 x 10 8 (221 ± 1 K, x = 0.153 ±0.076), where the associated temperatures and solute mole fraction aqueous compositions (x) are noted in parentheses.