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。 要形成降雨，它们必须迅速增长到至少 50-100 $\mu$m 的水滴。 观测表明，这个过程仅需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纠缠团聚不稳定性现象（Phys. Fluids 25, 085104, 2013）导致了水滴团聚体的形成，其水滴数密度显著增加。 纠缠团聚不稳定性机制比我们之前考虑的由湍流涡旋的离心效应引起的惯性团聚不稳定性更有效。 这是团聚体内碰撞-聚并速率强烈增强的原因。 本研究开发的水滴增长的平均场理论有助于解释在15-20分钟内从初始1微米大小的云滴迅速增长到40-50微米大小的云滴的观测现象。 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 the tangling clustering instability is much more effective than the previously considered by us the inertial clustering instability caused by the centrifugal effect of turbulent vortices. This is the reason of strong enhancement of the collision-coalescence rate inside the clusters. The mean-field theory of the droplet growth developed in this study can be useful for explanation of the observed fast growth of cloud droplets in warm clouds from the initial 1 micron size droplets to 40-50 micron size droplets within 15-20 minutes.