Cloud droplet number enhanced by co-condensation of organic vapours
Cloud droplet number enhanced by co-condensation of organic vapours
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DOI：
10.1038/ngeo1809
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发表时间：
2013-06-01
影响因子：
18.3
通讯作者：
McFiggans, Gordon
中科院分区：
文献类型：
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作者：
Topping, David;Connolly, Paul;McFiggans, Gordon
云对天气和气候有着深远的影响(1)。云的亮度 (2) 和寿命 (3,4) 由云滴数量浓度决定，而云滴数量浓度又由可用种子颗粒的数量决定。非挥发性大气颗粒上云滴的形成是众所周知的(5)。然而，大气中细颗粒物的挥发性范围很大(6,7)。半挥发性化合物与水的共缩合增加了颗粒形成云滴的倾向(8)，并对陆地生物圈和气候之间的反馈产生潜在影响(9)。在这里，我们系统地研究了云滴的形成，使用了云块模型，该模型扩展到包括在各种现实条件下半挥发性有机化合物的共凝结。随着空气团的上升和冷却，它所能容纳的有机蒸气的浓度会下降。因此，模拟的有机蒸气随着上升而变得越来越饱和，并因此在膨胀成云滴时凝结在不断生长的粒子上。我们表明，越来越多的挥发性物质的凝结增加了这些液滴的可溶质量，并促进了额外水的吸收，这反过来又导致了可行的云滴数量的大幅增加。我们认为半挥发性有机化合物与水蒸气的共凝结对云的辐射特性有重大影响。
Clouds profoundly influence weather and climate(1). The brightness(2) and lifetime(3,4) of clouds is determined by cloud droplet number concentration, in turn dictated by the number of available seed particles. The formation of cloud droplets on non-volatile atmospheric particles is well understood(5). However, fine particulate matter in the atmosphere ranges widely in volatility(6,7). Co-condensation of semi-volatile compounds with water increases a particle's propensity for cloud droplet formation(8), with potential consequences for feedbacks between the terrestrial biosphere and climate(9). Here we systematically study cloud droplet formation, using a cloud parcel model extended to include co-condensation of semi-volatile organic compounds under a broad variety of realistic conditions. As an air parcel rises and cools, the concentration of organic vapour that it can hold declines. Thus, the simulated organic vapours become increasingly saturated as they ascend, and so condense on growing particles as they swell into cloud droplets. We show that condensation of increasingly volatile material adds to the soluble mass of these droplets and facilitates the uptake of additional water, which leads, in turn, to a substantial increase in the number of viable cloud droplets. We suggest that the co-condensation of semi-volatile organic compounds with water vapour has a substantial impact on the radiative properties of clouds.