The retention of ammonia and sulfur dioxide during riming of ice particles and dendritic snow flakes: laboratory experiments in the Mainz vertical wind tunnel
The retention of ammonia and sulfur dioxide during riming of ice particles and dendritic snow flakes: laboratory experiments in the Mainz vertical wind tunnel
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冰粒和树枝状雪花形成过程中氨和二氧化硫的保留：美因茨垂直风洞的实验室实验
DOI：
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发表时间：
2013
影响因子：
2
通讯作者：
S. Borrmann
中科院分区：
文献类型：
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作者：
Nadine Blohn;K. Diehl;A. Nölscher;Alexander Jost;S. Mitra;S. Borrmann
在美因茨垂直风洞中进行了实验室实验，以确定在雾化过程中溶解在过冷云滴中的微量气体氨和二氧化硫的保留率。形成时的条件与大气混合相云相似：温度为−18℃~−5℃，液态水含量为1 ~ 1.5 g m−3，液滴半径为10 ~ 20 μm，液相浓度为1 ~ 22 mg/l。采用直径在6毫米至1.5厘米之间的浮冰颗粒和雪花作为收集器。定格后的保留系数，即冻结后留在冰相的物种的分数被确定。保留系数介于0.1和1.0之间，取决于微量气体的溶解度和解离度、液相浓度、环境空气温度和边缘收集器的形状。从化学家的观点来看，这可以用物质的有效亨利定律常数来解释，并在物理上用冷冻过程中从边缘收集器中去除潜热的速率来解释。从不同的实验案例中得到的参数化描述了保留系数作为温度的函数。总的来说，氨的平均滞留率为92±21%，与液相浓度无关，而二氧化硫的平均滞留率在低液相浓度下为53±10%，在高液相浓度下为29±7%。
Laboratory experiments were carried out in the Mainz vertical wind tunnel to determine the retention of the trace gases ammonia and sulfur dioxide dissolved in supercooled cloud droplets during riming. The conditions during riming were similar to the ones in atmospheric mixed phase clouds: temperatures from −18 °C to −5 °C, liquid water contents between 1 and 1.5 g m−3, liquid drop radii between 10 and 20 μm, liquid phase concentrations from 1 to 22 mg/l. As collectors, floating ice particles and snow flakes with diameters between 6 mm and 1.5 cm were used. After riming the retention coefficients, i.e. the fractions of the species which remained in the ice phase after freezing were determined. Retention coefficients lying between 0.1 and 1.0 were measured depending on the solubility and dissociation of the trace gas, liquid phase concentration, ambient air temperature, and shape of rimed collector. This can be explained from the chemists’ point of view by the effective Henry’s law constant of the species and physically with the rate of latent heat removal from the rimed collector during freezing. Parameterizations derived from the different experimental cases describe the retention coefficients as a function of temperature. In general, an average retention of ammonia of 92 ± 21 % was determined independently of liquid phase concentration while mean values for sulfur dioxide were 53 ± 10 % at low liquid phase concentrations and 29 ± 7 % at high liquid phase concentrations.