HAIL SUPPRESSION BY APPLICATION OF EXTERNAL ELECTRIC FIELD

The lightning is often followed in the cloud by a rapidly increasing intensifying echo and then by agush of rain or hail at the ground. The increase in radar reflectivity in small volumes of the cloudfollowing lightning suggested that the electric discharge is influencing the size of particles in the cloud.The analysis indicated that within 30 seconds after a lightning discharge, the mass of some dropletsincreased as much as 100-fold as the result of an electrostatic precipitation effect. Later observationsdisclosed that the rain gush phenomenon can also occur in regions of the cloud that are colder than 00Cand that here gush can be of hail or rain. During a lightning discharge maximum electric field (~10e.s.u.) is produced near the channel. It has been shown that action of a constant and uniform electricfield accelerated the condensation of water vapor by a factor depending upon the intensity 0f electricfield. It was shown that a droplet acquires a particular size under very low supersaturation under anelectric field, which would otherwise, require very high supersaturation. We have shown that in theresultant effect on a droplet due to an external electric field and the field induced due to the centraldipole, the rate of nucleation in water vapor condensation and ice glaciations is about 100 times morenear break-down for dry air, as compared to that in absence of electric field. The calculations show thatat a given relaxation time and temperature, the equivalent supersaturation decreases with increase inelectric field. Effective role of external electric field in nucleation has been applied to explore the hailsuppression phenomenon. It has been found that an application of a small external electric field isequivalent to a large supersaturation ratio. Large size ice crystals (hails) are split into smaller particles,so that damage caused by hails is reduced. At the same time, this happens at an early stage.