Further Laboratory Experiments on Aerosol Scavenging in Mixed Clouds to Assess the Role of Phoretic Forces and Particle Solubility

Abstract

Scavenging experiments have been performed in a cloud chamber inside a cold room with different aerosol particles: Paraffin particles, NaCl particles, Magnesium oxide particles, Carbon particles, Sahara dust particles. Essentially the experimental tests were carried on following the sequence of operations: the generation of the aerosol particles, their injection in the lower part of the cloud chamber, injection of water droplets in the whole chamber volume, nucleation of ice crystals, collection of ice crystals and their examination as for resulting scavenging efficiency. Evidence is given of the peculiar behaviour of soluble particles, individual and eventually inside mixed particles, leading to very much important scavenging efficiency, probably to be ascribed to aerodynamic capture. The evident peculiar behaviour of deliquescent particles can be oriented towards applications to an efficient abatement of specific effluents, on one side, and to weather modification experiments, both rain enhancement and hail prevention experiments.

Mechanism of Stefan Flow in the Collection of Particles on Evaporating/Condensing Surfaces: A Review

“…In the field of atmospheric science, researchers began to study the transport mechanism of Stefan flow when exploring the interaction of raindrops or ice crystals with aerosol particles. Vittori, 46 Hallet and Oraltay, 47 Oraltay and Hallet, 48 and Prodi et al 49 investigated by experiment the mechanism of aerosol particle collection in the mixed cloud where evaporating droplets and growing ice crystals coexist. The research results showed that the presence of supercooled droplets in the mixed cloud can effectively improve the collection efficiency of submicrometer particles on the surface of ice crystals.…”

“…The experimental studies in section show that the Stefan flow prevails over other particle transport mechanisms and pushes particles away from the evaporating surface. ,,− Meanwhile, the calculation results show that the phoretic force caused by evaporation can significantly enhance the deposition of submicrometer particles in the range of 0.01–1 μm particle size on the evaporating surface in most theoretical studies. Therefore, the particle collection efficiency by theoretical calculation is much higher than the experimental results. ,− ,− ,,,,, We suggest that the inconsistency between the theoretical calculation and the experimental results originates from the defects of the models.…”