Manipulating marine stratocumulus cloud amount and albedo: a process-modelling study of aerosol-cloud-precipitation interactions in response to injection of cloud condensation nuclei
Manipulating marine stratocumulus cloud amount and albedo: a process-modelling study of aerosol-cloud-precipitation interactions in response to injection of cloud condensation nuclei
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DOI：
10.5194/acp-11-4237-2011
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发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Feingold, G.
中科院分区：
文献类型：
--
作者：
Wang, H.;Rasch, P. J.;Feingold, G.
我们用一个云系分辨模式来研究海洋云增亮。我们研究了注入的气溶胶粒子作为云凝结核（CCN）是如何在海洋边界层内传输的，以及云中的额外粒子如何影响云微物理过程，并对动力学进行反馈。结果表明，云增亮的有效性很大程度上取决于气象条件和背景气溶胶条件。云对流增强在弱降水边界层和CCN限制条件下是非常有效的，之前是重和/或持续降水。在前一种情况下，额外的云凝结核通过大大减弱降水而在后一种情况下通过防止边界层崩溃来帮助维持云水。对于给定量的注入CCN，注入方法（即，喷雾器的数量和分布）对这些云凝结核的空间分布至关重要。区域覆盖率和注入颗粒的数量浓度都是关键因素，但两者都不总是比另一个更重要。同样数量的注入物质对强降水云或污染云的效果要差得多，而且在相对干燥的边界层中也是无效的，边界层支持低液态水路径的云。在污染情况和“干燥”情况下，CCN的注入增加了水滴数浓度，但降低了过饱和度和液态水路径。结果，云经历非常弱的对流增强，不管注射方法如何。
We use a cloud-system-resolving model to study marine-cloud brightening. We examine how injected aerosol particles that act as cloud condensation nuclei (CCN) are transported within the marine boundary layer and how the additional particles in clouds impact cloud microphysical processes, and feedback on dynamics. Results show that the effectiveness of cloud brightening depends strongly on meteorological and background aerosol conditions. Cloud albedo enhancement is very effective in a weakly precipitating boundary layer and in CCN-limited conditions preceded by heavy and/or persistent precipitation. The additional CCN help sustain cloud water by weakening the precipitation substantially in the former case and preventing the boundary layer from collapse in the latter. For a given amount of injected CCN, the injection method (i.e., number and distribution of sprayers) is critical to the spatial distribution of these CCN. Both the areal coverage and the number concentration of injected particles are key players but neither one always emerges as more important than the other. The same amount of injected material is much less effective in either strongly precipitating clouds or polluted clouds, and it is ineffective in a relatively dry boundary layer that supports clouds of low liquid water path. In the polluted case and "dry" case, the CCN injection increases drop number concentration but lowers supersaturation and liquid water path. As a result, the cloud experiences very weak albedo enhancement, regardless of the injection method.