Holographic measurements of inhomogeneous cloud mixing at the centimeter scale
Holographic measurements of inhomogeneous cloud mixing at the centimeter scale
复制标题
DOI：
10.1126/science.aab0751
复制
发表时间：
2015-10-02
期刊：
影响因子：
56.9
通讯作者：
Stith, Jeffrey L.
中科院分区：
文献类型：
--
作者：
Beals, Matthew J.;Fugal, Jacob P.;Stith, Jeffrey L.
大气云的光学特性和降水效率在很大程度上取决于湍流与其环境的混合。当云中液态水在混合后减少时，液滴可能在整个群体中均匀蒸发，或者在另一种极端情况下，一小部分液滴可能完全蒸发，而其余液滴不受影响。在这里，我们使用航空全息成像来可视化最小湍流尺度下的空间结构和液滴尺寸分布，从而观察它们对夹带和与晴空混合的响应。测量结果表明，湍流云是不均匀的，云和晴空性质之间的急剧转变持续到耗散尺度（< 1厘米）。局部液滴大小分布在数量密度上波动较大，但平均液滴直径几乎不变。
Optical properties and precipitation efficiency of atmospheric clouds are largely determined by turbulent mixing with their environment. When cloud liquid water is reduced upon mixing, droplets may evaporate uniformly across the population or, in the other extreme, a subset of droplets may evaporate completely, leaving the remaining drops unaffected. Here, we use airborne holographic imaging to visualize the spatial structure and droplet size distribution at the smallest turbulent scales, thereby observing their response to entrainment and mixing with clear air. The measurements reveal that turbulent clouds are inhomogeneous, with sharp transitions between cloud and clear air properties persisting to dissipative scales (< 1 centimeter). The local droplet size distribution fluctuates strongly in number density but with a nearly unchanging mean droplet diameter.