Effect of aerosol on trade cumulus cloud morphology
Effect of aerosol on trade cumulus cloud morphology
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DOI：
10.1029/2009jd011750
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发表时间：
2009-06
影响因子：
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通讯作者：
Hongli Jiang;G. Feingold;I. Koren
中科院分区：
文献类型：
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作者：
Hongli Jiang;G. Feingold;I. Koren
[1]对清洁和污染的气溶胶条件和若干不同网格尺寸的信风积云进行了大涡模拟，以探索(1)积云场对气溶胶扰动的微物理和形态响应以及(2)这些响应对分辨率的稳健性。云的大小分布符合负幂函数，表明随着分辨率的提高，越来越多的小云被分解。在最高分辨率模拟中的云量比在高分辨率模拟中高30%。受污染的云群比清洁的云群包含更多的较小的云。它们的对流频率较高，寿命较短。受污染的云层也往往有更高的云平均液态水含量。据推测，这些反应是在污染云的情况下，由云边缘更强的蒸发所引发的连锁反应的结果。在所有情况下，根据最近的卫星研究，最小的云要么主导云量和云层反射率，要么对云量和云层反射率有显著贡献。云量和液态水路径对气溶胶变化的响应很大程度上取决于对“云”的定义，这表明在对这些响应进行参数化之前应谨慎行事。
[1] Large-eddy simulations of trade wind cumulus clouds are conducted for clean and polluted aerosol conditions and at a number of different grid sizes to explore (1) the microphysical and morphological responses of fields of cumulus to aerosol perturbations and (2) the robustness of these responses to resolution. Cloud size distributions are shown to be well approximated by a negative power law function indicating that as resolution increases, more and more small clouds are resolved. Cloud fraction in the highest-resolution simulations is 30% higher than in the coarse-resolution simulations. Polluted cloud populations contain higher numbers of smaller clouds than clean cloud populations. Their frequency of convection is higher and lifetimes are shorter. The polluted clouds also tend to have higher cloud-averaged liquid water contents. It is hypothesized that these responses are a result of a chain reaction set off by stronger evaporation at cloud edges in the case of polluted clouds. In all cases, the smallest clouds either dominate or contribute significantly to cloud fraction and cloud reflectance, in accord with recent satellite studies. The response of cloud fraction and liquid water path to aerosol changes is shown to be strongly dependent on the definition of what constitutes a “cloud,” suggesting that caution be exercised before parameterizing these responses.