论文摘要
云层冰晶的形成和降水过程中闪电诱导等离子体的潜在影响 几十年一直颇有争议。我们在此阐述了大型云层模拟室观察所得的激光产生的水和冰晶云体等离子体通道间的相互作用。冰和超冷水并存的典型风暴云条件下，没有检测发现冰晶形成或沉淀过程中等离子体通道所受的直接影响。然而在薄卷云冰晶云层的典型条件下，等离子体通道诱发了冰晶倍增意外强劲的影响。在几分钟内，激光作用就能引发室内总体冰晶粒子数量密度的大量增殖至高达百倍，即使只有室内容积的1/10-1/9暴露于等离子体通道中。新形成的冰粒迅速降低了冰饱和度的水蒸汽压力， 从而增加了云层光学厚度使之增加三个数量级。依赖于激光丝和所得等离子体离子的水蒸汽凝聚中的冰粒完全蒸发的模型再现了我们的实验结果。这一惊人效果可能会打开有关上层对流层中水蒸汽和冰晶遥感的新视角。
Abstract
Potential impacts of lightning-induced plasma on cloud ice formation and precipitation have been a subject of debate for decades. Here, we report on the interaction of laser-generated plasma channels with water and ice clouds observed in a large cloud simulation chamber. Under the conditions of a typical storm cloud, in which ice and supercooled water coexist, no direct influence of the plasma channels on ice formation or precipitation processes could be detected. Under conditions typical for thin cirrus ice clouds, however, the plasma channels induced a surprisingly strong effect of ice multiplication. Within a few minutes, the laser action led to a strong enhancement of the total ice particle number density in the chamber by up to a factor of 100, even though only a 10−9 fraction of the chamber volume was exposed to the plasma channels. The newly formed ice particles quickly reduced the water vapor pressure to ice saturation, thereby increasing the cloud optical thickness by up to three orders of magnitude. A model relying on the complete vaporization of ice particles in the laser filament and the condensation of the resulting water vapor on plasma ions reproduces our experimental findings. This surprising effect might open new perspectives for remote sensing of water vapor and ice in the upper troposphere.