Transport And Communications

Cloud seeding is the way of artificial weather modification to change the amount or kind of precipitation. This is realized by the dispersion of substances serving as condensation or crystallization nuclei, which affect microphysic processes inside the cloud. The greatest effect of infication is achieved by the artificial production of ice nuclei in the cloud consisting of supercooled water droplets. For this purpose, different chemical reagents are applied, usually by airplane or ground generator. The most common way is dispersion of solid carbon dioxide (CO2). As its evaporation temperature falls significantly, this results in formation of a certain amount of ice crystals. Another widespread method is the introduction of silver iodide (AgI) into the cloud. The cooling in the air leads to creation of microscopic ice crystals. Cloud, eventually fog seeding is of great economic importance not only in agricultural (water source management in tropical and subtropical areas, crop protecion etc.), but also in industrial and transport sectors. Especially in air transport it contributes to dissipation or reduction of hazardous aviation weather phenomena occuring near or at the airport. The aim of this paper is to explain the actual activities in the area of weather modification for the purpose of influencing clouds and precipitation.