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首页> 外文期刊>Nature >Surface tension prevails over solute effect in organic-influenced cloud droplet activation
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Surface tension prevails over solute effect in organic-influenced cloud droplet activation

机译：在有机影响的云滴活化中，表面张力胜于溶质效应

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摘要

The spontaneous growth of cloud condensation nuclei (CCN) into cloud droplets under supersaturated water vapour conditions is described by classic Kohler theory(1,2). This spontaneous activation of CCN depends on the interplay between the Raoult effect, whereby activation potential increases with decreasing water activity or increasing solute concentration, and the Kelvin effect, whereby activation potential decreases with decreasing droplet size or increases with decreasing surface tension, which is sensitive to surfactants(1). Surface tension lowering caused by organic surfactants, which diminishes the Kelvin effect, is expected to be negated by a concomitant reduction in the Raoult effect, driven by the displacement of surfactant molecules from the droplet bulk to the droplet-vapour interface(3,4). Here we present observational and theoretical evidence illustrating that, in ambient air, surface tension lowering can prevail over the reduction in the Raoult effect, leading to substantial increases in cloud droplet concentrations. We suggest that consideration of liquid-liquid phase separation, leading to complete or partial engulfing of a hygroscopic particle core by a hydrophobic organic-rich phase, can explain the lack of concomitant reduction of the Raoult effect, while maintaining substantial lowering of surface tension, even for partial surface coverage. Apart from the importance of particle size and composition in droplet activation, we show by observation and modelling that incorporation of phase-separation effects into activation thermodynamics can lead to a CCN number concentration that is up to ten times what is predicted by climate models, changing the properties of clouds. An adequate representation of the CCN activation process is essential to the prediction of clouds in climate models, and given the effect of clouds on the Earth's energy balance, improved prediction of aerosol-cloud-climate interactions is likely to result in improved assessments of future climate change.
机译：经典的科勒理论（1,2）描述了在过饱和水蒸气条件下云凝结核（CCN）自发地生长为云滴。 CCN的这种自发活化取决于Raoult效应与开尔文效应之间的相互作用，Raoult效应随水活度降低或溶质浓度升高而增加，开尔文效应则随液滴尺寸的减小而降低，或随着表面张力的降低而增加。表面活性剂（1）。由表面活性剂引起的表面张力降低（其降低了开尔文效应），可以预期是由于表面活性剂分子从液滴本体向液滴-蒸汽界面的位移所致，拉乌特效应随之降低（3,4） 。在这里，我们提供的观察和理论证据表明，在环境空气中，表面张力的降低可能胜过Raoult效应的降低，从而导致云滴浓度显着增加。我们建议考虑液-液相分离导致吸湿性颗粒核被富含疏水有机物的相完全或部分吞噬，这可以解释缺乏同时降低Raoult效应，同时保持表面张力显着降低的原因，即使是部分表面覆盖。除了粒径和组成在液滴活化中的重要性外，我们还通过观察和建模表明，将相分离效应纳入活化热力学可以导致CCN数浓度高达气候模型预测值的十倍，从而变化云的性质。 CCN激活过程的充分表示对于预测气候模型中的云至关重要，并且鉴于云对地球能量平衡的影响，改进的气溶胶-云-气候相互作用的预测可能会改善对未来气候的评估更改。

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  • 来源
    《Nature》 |2017年第7660期|637-641|共5页
  • 作者

    Ovadnevaite Jurgita; Zuend Andreas; Laaksonen Ari; Sanchez Kevin J.; Roberts Greg; Ceburnis Darius; Decesari Stefano; Rinaldi Matteo; Hodas Natasha; Facchini Maria Cristina; Seinfeld John H.; Dowd Colin O;

  • 作者单位

    Natl Univ Ireland Galway, Sch Phys, Galway, Ireland|Natl Univ Ireland Galway, Ctr Climate & Air Pollut Studies, Galway, Ireland;

    McGill Univ, Dept Atmospher & Ocean Sci, Montreal, PQ, Canada;

    Finnish Meteorol Inst, Helsinki, Finland|Univ Eastern Finland, Dept Appl Phys, Kuopio, Finland;

    Ctr Natl Rech Meteorol, 42 Ave Gaspard Coriolis, F-31057 Toulouse, France;

    Ctr Natl Rech Meteorol, 42 Ave Gaspard Coriolis, F-31057 Toulouse, France|Scripps Inst Oceanog, 9500 Gilman Dr,0221, La Jolla, CA 92093 USA;

    Natl Univ Ireland Galway, Sch Phys, Galway, Ireland|Natl Univ Ireland Galway, Ctr Climate & Air Pollut Studies, Galway, Ireland;

    CNR, Inst Sci Atmosfera, I-40129 Bologna, Italy;

    CNR, Inst Sci Atmosfera, I-40129 Bologna, Italy;

    CALTECH, Div Chem & Chem Engn, Mail Code 210-41, Pasadena, CA 91125 USA|Portland State Univ, Dept Environm Sci & Management, Portland, OR 97201 USA;

    CNR, Inst Sci Atmosfera, I-40129 Bologna, Italy;

    CALTECH, Div Chem & Chem Engn, Mail Code 210-41, Pasadena, CA 91125 USA;

    Natl Univ Ireland Galway, Sch Phys, Galway, Ireland|Natl Univ Ireland Galway, Ctr Climate & Air Pollut Studies, Galway, Ireland;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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