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J. Rosinski

Abstract

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J. Rosinski

Abstract

Population of cloud droplets in a cloud may be decreased under some circumstances by their removal (along with other particles) by an ice crystal growing on an ice-forming nucleus. Further condensation of water vapor should take place on remaining cloud droplets, which should consequently grow to larger sizes.

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J. Rosinski

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 μ in diameter when solid (ice crystal) and liquid (supercooled cloud droplet) phases are present simultaneously. Particles larger than 5 μ in diameter were scavenged primarily by impaction. On many occasions, concentration of particles larger than 100 μ 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.

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J. Rosinski

Abstract

By melting concentric layers of ice, the size distribution and concentration of solid water-insoluble particles accumulated in hailstones were determined for three hailstorms in Colorado. It was found that in approximately 50 per cent of the hailstones analyzed, particle concentration in ice increased with radial distance. Following an equation derived for this category of hailstones, a relationship is shown among liquid water content of a cloud, concentration of solid particles in cloud droplets, speed of the hailstone, and its residence time in the atmosphere. Spatial distribution of solid particles in hailstones was also determined by slicing hailstones and subsequently separating particles from the ice by sublimation under low pressure. It was found that some of the hailstones analyzed were oriented during their growth.

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J. Rosinski and F. Parungo

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Silver iodide particles deposited on vegetation may photolyse and combine with natural terpenes from tree oils to form compounds which either themselves become aerosols, or become attached to aerosol particles. In either case the new compounds may become active centers acting as freezing nuclei. Silver iodide particles may persist for several months when deposited on coniferous trees, and may release variable doses of such freezing nuclei during that time. Although the concentrations of ice nuclei so produced are probably too small to influence precipitation, they may nevertheless contaminate large areas and thus may be significant for long-range research programs concerned with measuring natural concentrations of freezing nuclei.

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J. Rosinski and C. T. Nagamoto

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Silver chloride, bromide and iodide hydrosol particles were studied as freezing nuclei. Ice nucleation was enhanced through the exchange of iodine ions on the surface of solid silver iodide, using iodine monobromide. Drops containing AgI in concentrations larger than 10−4 gm cm−3 froze between −3 and −3.4C in the presence of iodine monobromide, supplied from the reaction between potassium iodide and N-bromosuccinimide. These results give support to Fukuta-Paik calculations showing that Ag+ sites in AgI are responsible for the enhancement of ice nucleability.

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J. Rosinski and R. H. Snow

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The size distribution of secondary particulate matter, formed from condensing vapors in meteoric trains in the meteoric evaporating zone, was calculated. The diameters of the particles were found to be approximately proportional to the size of the meteor. The particles were calculated to be below 100 A in diameter, and the median volume diameters ranged from 4.5 to 80 A one min after evaporation. The average concentration of secondary particles formed from meteoric showers was found to be higher than the concentration from the steady-state influx of sporadic meteors.

From these results, the majority of the freezing nuclei in Bowen's hypothesis might be interpreted to be connected with the secondary particles formed in meteoric trails. If these particles serve as freezing nuclei, then freezing nuclei should be of similar chemical composition. The presence of larger secondary particles in the wakes of very bright meteors may contribute to the formation of noctilucent clouds.

Bowen's hypothesis should be re-evaluated and the role of the secondary meteoric matter in the earth's atmosphere clarified.

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J. Rosinski and T. C. Kerrigan

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Variable concentrations of different sized water-insoluble particles were found in bulk rainwater and single raindrops (liquid phase) and in hailstones (solid phase) collected from severe thunderstorms in the Colorado-Nebraska region. It was possible to draw the following conclusions from studies of aerosol particles transferred into the liquid phase of the storm: 1) aerosol particles constitute an intrinsic part of a convective cloud in a severe thunderstorm; 2) the size distribution of cloud droplets is extended to larger sizes by thepresence of giant aerosol particles (> 75 n diameter); 3) giant aerosol particles begin to accrete cloud droplets as soon as they enter the cloud; and 4) the size distribution of raindrops falling at the leading edge of a severe storm depends on the concentration of giant aerosol particles ingested by the storm.

The presence of different sized particles in the solid phase led to the following conclusions: 1) transparenthailstones are formed from the frozen Equid phase of a cloud (cloud droplets and raindrops) around giantaerosol particles, some of the giant aerosol particles acting as ice-forming nuclei at temperatures as warmas - 6C; 2) milky hailstones originate in the presence of ice crystals which have grown through the liquid-vapor-solid phase transition; 3) the majority of ice-forming nuclei in milky hailstones are particles between6 and 12 y. diameter, this size range being the result of particle separation by size in an ascending cloud; and4) detailed analysis of particulate matter present in different forms of ice in mixed hailstones provides information on the environmental conditions during their formation and growth.

A numerical model shows possible conditions for the formation of raindrops around giant aerosol particles. The models calculations also predict strong separation of different sized aerosol particles ingested by the storm. The latter was verified in samples from a storm in which rainfall contained no 50-75 μ diameterparticles, while hailstones contained up to 2300 particles in the same size range, per gram of ice.

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C. T. Nagamoto, J. Rosinski, and G. Langer

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J. Rosinski, G. Langer, and C. T. Nagamoto

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