Simulation of the effects of increasing cloud condensation nuclei on mixed-phase clouds and precipitation of a front system
Simulation of the effects of increasing cloud condensation nuclei on mixed-phase clouds and precipitation of a front system
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DOI：
10.1016/j.atmosres.2010.02.005
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发表时间：
2010-05
影响因子：
5.5
通讯作者：
Chao‐Tzuen Cheng;Wei‐Chyung Wang;Jen‐Ping Chen
中科院分区：
文献类型：
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作者：
Chao‐Tzuen Cheng;Wei‐Chyung Wang;Jen‐Ping Chen
云凝结核（CCN）浓度的增加通常会导致暖云降水量的增加和降水量的减少，但它对混合云降水的影响不太明显。在这里，散装公式半两个时刻的混合相云方案与区域模式研究这方面的前系统与对流。虽然这种云方案比云解析模型中使用的大多数详细的箱解析云方案要简单得多，但CCN效应的某些特征得到了合理的模拟。结果表明，第一和第二间接效应的模拟和冰相降水有效地从对流层上层的云水，导致较弱的第一间接效应。敏感性模拟表明，虽然增加CCN数的结果在更多的云滴和冰，其对地面降水的影响取决于减少暖雨生产和减少/增加冰相降水之间的相互作用。因此，云滴的增加增强了水亚饱和环境中冰粒的扩散生长，但抑制了水过饱和环境中的冰粒扩散生长。此外，霜的变化取决于由于更多云滴的增强和由于较小云滴的抑制之间的平衡。对于本文研究的情况，降水对CCN数的变化的响应是非线性的，在高CCN浓度环境中，降水减少，但在低CCN浓度环境中，降水没有明显的趋势。
Increasing cloud condensation nuclei (CCN) concentration usually leads to increasing cloud albedo and decreasing precipitation for warm clouds but its effect on the precipitation of mixed-phase clouds is less clear. Here, a bulk-formula semi-two-moment mixed-phase cloud scheme is incorporated with a regional model to study this aspect on a front system associated with convection. Although this cloud scheme is comparably simpler than most detailed bin-resolving cloud schemes used in cloud resolving models, certain features of CCN effects are reasonably simulated. Results show that both the first and the second indirect effects are simulated and that ice-phase precipitation effectively removes cloud water from the upper troposphere, leading to weaker first indirect effects. Sensitivity simulations show that although increasing CCN number results in more cloud drops and ice, its effect on surface precipitation depends on the interplay between the decreased warm-rain production and the decreased/increased ice-phase precipitation. The increase in cloud drops consequently enhances the diffusional growth of ice particles in water-subsaturated environments but inhibit it in water-supersaturated environments. Moreover, the change in riming depends on the balance between the enhancement due to more cloud drops and the suppression due to smaller cloud drops. For the case studied here, the precipitation responds nonlinearly to CCN number change, causing precipitation decrease in high CCN concentration environments but showing no clear tendency in low CCN concentration environments.