Cloud albedo enhancement by surface-active organic solutes in growing droplets
Cloud albedo enhancement by surface-active organic solutes in growing droplets
复制标题
DOI：
10.1038/45758
复制
发表时间：
1999-09-16
期刊：
影响因子：
64.8
通讯作者：
Charlson, RJ
中科院分区：
文献类型：
--
作者：
Facchini, MC;Mircea, M;Charlson, RJ
了解地球大气层中云的特性目前受到基本困难的限制，难以充分描述云滴成核和生长的过程。小水滴数量的微小变化可能会显著影响云密度（1）以及降水的形成。基于实验室研究和理想化的原子核组成的云形成模型表明，有机溶质显著降低了表面张力（2）--决定液滴数量的参数之一--但是缺乏关于大气中有机物质的组成和性质的数据排除了现实的实验室或模型研究。在这里，我们报告测量真空蒸发样品的云水从波河流域，意大利，显示了表面张力的大幅下降，高达约三分之一相对于纯水，为现实浓度的有机溶质预计存在于不断增长的液滴。如此大的表面张力变化，如果它们发生在云液滴的临界尺寸附近的成核，导致增加的液滴人口，因此在云的对流。忽略这种影响所产生的误差估计与其他计算的气溶胶对太阳辐射散射和吸收的直接和间接影响相当（3）。
Understanding the properties of clouds in the Earth's atmosphere is currently limited by difficulties at the fundamental level of adequately describing the processes of cloud droplet nucleation and growth. Small changes in droplet population may significantly influence cloud albedo(1) as well as formation of precipitation. Models of cloud formation based on laboratory studies with idealized composition of nuclei suggest that organic solutes significantly lower surface tension(2)-one of the parameters determining droplet population-but the lack of data on composition and properties of the organic material in the atmosphere precludes realistic laboratory or model studies. Here, we report measurements on vacuum-evaporated samples of cloud water from the Po Valley, Italy, that show a large decrease in surface tension, by up to about one-third relative to pure water, for realistic concentrations of organic solutes expected to exist in growing droplets. Such large surface-tension changes, if they occur in cloud droplets near the critical size for nucleation, lead to an increase in droplet population and hence in cloud albedo. The error produced in ignoring this effect is estimated to be comparable to other calculated direct and indirect influences of aerosols on scattering and absorption of solar radiation(3).