Insoluble Particles in Hail and Rain

Abstract

Varying concentrations of different sized, solid, water-insoluble particles in rainwater and hailstones collected during thunderstorms indicate the existence of several scavenging mechanisms of micron-size particles. It is shown that Stefan flow is probably the predominant mechanism of in-cloud scavenging of particles 1.5?5 ? in diameter when solid (ice crystal) and liquid (supercooled cloud droplet) phases are present simultaneously. Particles larger than 5 ? in diameter were scavenged primarily by impaction. On many occasions, concentration of particles larger than 100 ? diameter in rainwater was found to be inversely proportional to rainfall intensity. Studies of spatial distribution of solid particles in hailstones should be supplemented by isotopic analysis.