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Results of experimental investigations of an influence of the model hydrometeors on an electromagnetic radiation of the discharge phenomena initiated in an artificial thundercloud have been presented. It was established that the characteristics of an electromagnetic radiation of the cloud discharges initiated by the model hydrometeor groups in an artificial thundercloud depend on the location of the cells of a different polarity relative to the ground, as well as on the place of an introduction of the large hydrometeor arrays into the gap between the cells. It was determined that the character of the registered electromagnetic radiation of the discharge phenomena initiated by the model hydrometeor groups in the artificial thundercloud was close to the character of the powerful bipolar impulses of very high frequency registered for the cloud discharges and during the beginning stage of a downward lightning formation. It was proposed that the arrays of a large hail in a thundercloud could provoke the discharge phenomena significantly modifying the characteristics of the electromagnetic radiation of the cloud discharges. It was experimentally shown that the introduction into the artificial thundercloud of the model hydrometeor groups combined in a common system by the dielectric string can sufficiently decrease a power and the duration of the impulses of an electromagnetic radiation of the initiating discharge phenomena.

Results of physical modeling of how arrays of large model hydrometeors exert an influence on processes forming subsequent negative lightning strikes are presented. The modeling involved a system of artificial thunderstorm cells. It has been shown for the first time that the introduction of an array of large model hydrometeors to the space between negatively charged cells significantly increases the probability of the formation of a subsequent discharge, total length of the discharge system, and magnitude of the neutralized charge. The influence of hydrometeors on parameters of current pulses of the first and subsequent discharges has been established. The results obtained can be used in developing methods of artificial stimulation of multistrike lightning and directed discharging of a thunderstorm cloud.

Basic provisions of the scientific and engineering fundamentals of the methods of an artificial initiation of the downward lightning and intracloud lightning by the model hydrometeor arrays have been formulated. The key role played by the model hydrometeor size and form on the probability of an artificial initiation of the downward lightning and intracloud lightning has been established. Volume hydrometeors of centimeter size are tailored for such goals. Dividing of the model hydrometeors on the five classes differing on the electric field amplification coefficient has been proposed. Model hydrometeors with the amplification coefficient from 5 to 19 will be the most optimal for an artificial lightning initiation. It was found that the requirements for the sizes and parameters of the model hydrometeor families and to the places of their introduction in a thundercloud will be determined in most by the effect of the earlier appearance of the avalanche corona on the hydrometeors. It discharges the nearest parts of the thunderstorm cells leading to the local decreasing of the field strength, probability of the streamer corona initiation, and its transition into the volume leader. It was determined that the combining of the model hydrometeors in the group by the dielectric string or tape and the simultaneous introduction in thundercloud of some hydrometeor arrays will significantly increase the probability of the artificial initiation of the intracloud lightning and lightning “cloud–ground,” and the successful discharging of a thundercloud. Moreover, the minimal linear sizes of separate hydrometeor groups should be more than several dozens of centimeters. Some variants of the disposition of the model hydrometeor groups in a thundercloud (near the bottom boundary of the thunderstorm cell, inside the thunderstorm cell, and in the space between the thunderstorm cells) when the most optimal conditions for the initiation of the intracloud lightning and lightning “cloud—ground” are provided, have been proposed.

We have experimentally studied how arrays of model coarse hydrometeors influence the initiation and propagation of discharge between an artificial-thunderstorm cell of negative or positive polarity and the ground. It is established for the first time that the probability of initiation and stimulation of a channeled discharge between negatively or positively charged cloud and the ground significantly depends on the shape and size of coarse hydrometeors occurring near the thunderstorm cell boundaries. The obtained results can be used in developing methods for the artificial initiation of the cloud–ground type lightning of both polarities and targeted discharge of thunderstorm clouds.

The results of experimental simulation of the influence of hydrometeor groups on the probability of initiation of spark channel discharges between an artificial thunderstorm cell of negative or positive polarity and the ground were presented. It has been discovered that there is a significant influence of the kind of hydrometeors and the method of their combination into a group on the initiation and stimulation of sparkdischarge propagation from an artificial thunderstorm cell. It has been revealed that injection of the groups of plate-rhombus hydrometeors sharply increases the probability of initiation of channel discharge from a negatively charged artificial cell. It has been established that volume-cylinder hydrometeors display an analogous behavior for a positively charged cell. It has been found that the simulation of accelerated formation of the spark discharge between neighboring hydrometeors in the group is a necessary condition for the initiation and stimulation of the channel-discharge propagation between the cloud and the ground. It has been revealed that a dielectric string or dielectric tape can be used for such purposes. A multifactor physical picture of hydrometeor influence on the initiation and stimulation of the spark channel discharge between an artificial thunderstorm cell and the ground has been proposed. This may result in promising methods of artificial initiation of lightning using arrays of model hydrometeors.

The initiation of discharge by model hydrometeors between an artificial-thunderstorm cell (aerosol cloud) of negative or positive polarity and ground has been experimentally studied. It is established for the first time that the conditions of cloud–ground spark discharge initiation by hydrometeors, as well as the characteristics of discharge significantly depend on the polarity of charged cloud. The effect of hydrometeor arrays can be manifested by the cloud–ground lightning initiated in a thundercloud and used for developing scientific principles of artificial lightning discharge.