Abstract
AgI-type pyrotechnics are widely used in the field of weather modification, as a kind of artificial ice nuclei. However, their precipitation yield remains an intensively studied area. In this paper, we present a study of AgI-type pyrotechnic nucleant-induced water condensation promoted by femtosecond laser filaments in a cloud chamber. It is found that when 50-ml sample was irradiated by the laser filaments, the particles condensed on the glass slide are more soluble and slightly larger (5-15 μm). The irradiation of the laser filament on the nucleant rarely induces the generation of particles of sizes larger than 1 μm; however, it increases the decay time of particles from 13 to 18 min by the creation of numerous small particles. The amount of snow on the cold bottom plate increases by 4.2-13.1% in 2 h, compared to that without the irradiation of the laser filament. These results are associated with the production of high-concentration HNO3 by the laser filament. The concentration of HNO3 in the melt water increases by more than ten times when the sample was irradiated by the laser filaments.
Highlights
Artificial weather modification has always been an aspiration of people for the control of disastrous weather, such as hail, flood, heavy snowfall, or drought
The results indicate that the femtosecond laser filament has a positive effect on hygroscopicity, and of the number density and size of pyrotechnically generated aerosol particles
We investigated the AgI-type pyrotechnic nucleant-induced water condensation promoted by a femtosecond laser filament in a cloud chamber
Summary
Artificial weather modification has always been an aspiration of people for the control of disastrous weather, such as hail, flood, heavy snowfall, or drought. AgI is an important manmade ice nucleus for the catalyzing of cold clouds in weather modification, at temperatures from −5 to −20 °C [1,2,3]. In practical applications, AgI is typically prepared for pyrotechnics by mixing with flammable compounds. In order to increase the nucleation effectiveness (the number of particles nucleated per gram of nucleant) of the AgI pyrotechnic in the cloud, hygroscopic salts are mixed as well. The nucleation effectiveness of the AgI pyrotechnic mixed with KCl or KI is very high, reaching 1012–1013 /g [4,5,6,7]. The artificial ice nuclei can be rapidly activated if there is sufficient amount of supercooled water in the cold cloud. The activation time is approximately a few seconds to 20 min
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