Tuesday, 11 January 2005: 11:30 AM
On the stochastic nature of droplet growth by coalescence
Recently, Kostinski and Shaw (BAMS, accepted for publications) suggested, via simple arguments, that warm rain initiation can occur within the proverbial 20 to 30 minutes, without having to appeal to giant aerosols or to droplet clustering. Standard turbulent energy cascade under realistic conditions appears sufficient to trigger rain formation. This is due, in large measure, to the fact that regardless of the initial size, the fastest one-in-a-million droplets, required for warm rain initiation, grow about ten times faster than the average droplet. I review these theoretical ideas, focusing on the role of pronounced fluctuations in cloud droplet growth, punctuated by coalescence events, and explore possible implications of these fluctuations in cloud seeding and weather modification.