Broadening of Cloud Droplet Size Spectra by Stochastic Condensation : Effects of Mean Updraft Velocity and CCN Activation
Broadening of Cloud Droplet Size Spectra by Stochastic Condensation : Effects of Mean Updraft Velocity and CCN Activation
复制标题
随机凝结拓宽云滴尺寸谱：平均上升气流速度和 CCN 激活的影响
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
R. Caballero
中科院分区：
文献类型：
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作者：
G. Sardina;S. Poulain;L. Brandt;R. Caballero
采用大涡模拟方法研究了均匀各向同性湍流中云滴的凝结生长。作者研究了平均上升气流速度和云凝结核（CCN）的化学成分对水滴生长的作用。结果表明，一个平均恒定的上升气流速度叠加到湍流场减少了单独的湍流波动引起的液滴尺寸谱的展宽。扩展了作者以前关于随机凝结的结果，作者介绍了一种新的理论估计的液滴尺寸谱加宽，占这种上升气流速度效应。当液滴达到临界尺寸时，观察到光谱展宽的类似减少，这取决于CCN的化学组成。与液滴表面成比例的液滴半径分布的平方的分析表明，对于大颗粒，分布是纯高斯的，而对于较小颗粒，其变得强烈非高斯，左尾的特征在于雾度活化半径周围的峰。这种分布可以显着影响后期阶段的液滴增长，涉及湍流碰撞，因为碰撞概率内核取决于液滴的大小，这意味着需要新的特定的封闭模型来捕捉这种效果。
The authors study the condensational growth of cloud droplets in homogeneous isotropic turbulence by means of a large-eddy simulation (LES) approach. The authors investigate the role of a mean updraft velocity and of the chemical composition of the cloud condensation nuclei (CCN) on droplet growth. The results show that a mean constant updraft velocity superimposed onto a turbulent field reduces the broadening of the droplet size spectra induced by the turbulent fluctuations alone. Extending the authors’ previous results regarding stochastic condensation, the authors introduce a new theoretical estimation of the droplet size spectrum broadening that accounts for this updraft velocity effect. A similar reduction of the spectra broadening is observed when the droplets reach their critical size, which depends on the chemical composition of CCN. The analysis of the square of the droplet radius distribution, proportional to the droplet surface, shows that for large particles the distribution is purely Gaussian, while it becomes strongly non-Gaussian for smaller particles, with the left tail characterized by a peak around the haze activation radius. This kind of distribution can significantly affect the later stages of the droplet growth involving turbulent collisions, since the collision probability kernel depends on the droplet size, implying the need for new specific closure models to capture this effect.
影响因子：
56.9
作者：
Beals, Matthew J.;Fugal, Jacob P.;Stith, Jeffrey L.
通讯作者：
Stith, Jeffrey L.