标题： 湍流分层大气中由于缠绕-聚类不稳定性导致的雨滴形成加速 显示英文标题

标题： Acceleration of raindrops formation due to tangling-clustering instability in turbulent stratified atmosphere

摘要： 水蒸气在活跃的云凝结核上的冷凝产生了微米大小的水滴。 要形成雨水，它们必须迅速增长到至少 50-100 $\mu$m 的水滴。 观测表明，这一过程仅需15-20分钟。 这种快速增长的未解物理机制对于理解和模拟降雨至关重要，被称为“降雨形成中的冷凝-聚并瓶颈”。 我们表明，最近发现的小水滴在温度分层湍流中的缠绕聚集不稳定性现象（Phys. Fluids 25, 085104, 2013）导致了水滴簇的形成，水滴数密度显著增加。 缠绕聚集不稳定性机制比之前考虑的纯惯性聚集（由湍流涡旋的离心效应引起）更为有效。 这是簇内碰撞-聚并速率显著增强的原因。 我们对水滴增长的分析解释了在15-20分钟内，温暖云中初始1 $\mu$m 大小的水滴增长到40-50 $\mu$m 大小的水滴的观测结果。 显示英文摘要

摘要： Condensation of water vapor on active cloud condensation nuclei produces micron-size water droplets. To form rain, they must grow rapidly into at least 50-100 $\mu$m droplets. Observations show that this process takes only 15-20 minutes. The unexplained physical mechanism of such fast growth, is crucial for understanding and modeling of rain, and known as "condensation-coalescence bottleneck in rain formation". We show that the recently discovered phenomenon of the tangling clustering instability of small droplets in temperature-stratified turbulence (Phys. Fluids 25, 085104, 2013) results in the formation of droplet clusters with drastically increased droplet number densities. The mechanism of tangling clustering instability is much more effective than the previously considered pure inertial clustering caused by the centrifugal effect of turbulent vortices. This is the reason of strong enhancement of the collision-coalescence rate inside the clusters. Our analysis of the droplet growth explains the observed fast growth of cloud droplets in warm clouds from the initial 1 $\mu$m size droplets to 40-50 $\mu$m size droplets within 15-20 minutes.