Modification of mixed phase clouds.
The basic group of weather modification methods of mixed phase clouds deals with cloud phase instability of cloud environment determined by long-term existence in clouds of extensive zones with supercooled liquid droplets (up to temperatures minus 35°-40°С). At introduction of artificial ice embryonic particles into such zones it begins the process of conversion of water pair from supercooled drops to these particles because saturating an aqueous tension over ice is less than above water, because of what the supercooled droplets of a fog evaporate and ice crystals grow up to the sizes of precipitation particles much faster than droplets.
Two methods of artificial increase of quantity of the additional crystallization centers are applied in works on weather modification:
Introduction of cold reagents in zones with supercooled liquid water droplets, i.e. substances which evaporation causes sharp local decrease of temperature resulting to freezing cloudy droplets in this zone. Granulated carbonic acid (dry ice CO2), which has temperature -70°С and liquid nitrogen (N2) having the temperature of boiling -178°С are used for these purposes. Airborne carbon dioxide complexes are applied to introduction of granulated carbonic acid into clouds. The cloud seeding by liquid nitrogen is made with the help of airborn nitric generators of fine-dispersed particles of ice, GMCHL-A.
The second way of artificial crystallization of the supercooled droplets is the introduction of aerosols of silver iodide AgI into a cloud. Particles of AgI not influencing directly on temperature of air, carry out function of artificial nucleuses crystallization, i.e. they play a role of a substrate for growth of ice particles, as their crystal structure is isomorphous to ice. The aerosols of silver iodide are injected into a cloud by shooting PV-26 flares at flight of the plane near to the cloud tops. Each PV-26 flare contains 40 grams of pyrotechnic compound of silver iodide and produce 5х1012 ice nucleuses per 1 gram of pyrotechnic material at temperature -10°С. The length of an active smoking track is 1 km.
Suppression of development of convective clouds.
Methods, used for this purpose, is based on convective instability of the atmosphere. The droping of self-opening packages with coarse-dispersion powders (more often — cement) in top of a cloud is applied to artificial initiation of in-cloud descending movements. In this case a quasiordered descending air flow is created in the top part of a cloud, due to which the structure of the ordered air movements in a zone of top of a cloud is broken. In a field of a horizontal wind there is reorganization and inflow of dry near-cloud air begins inside to Cu, Cb. The dry air is cooled because of evaporation of cloudy particles in it, that promotes its lowering inside of a cloud (on hundreds meters), what even can generate a powerful descending flow.
In the prevailing majority of cases such seeding results to partial (more often — complete) destruction of clouds. The intensity of dissipation process in Cu-Cb clouds is practically identical both in warm and in the cooled clouds.