Statistical analysis of glaciogenic seeding impact on radar and lightning characteristics of hail clouds

The effect of glaciogenic seeding on 40 hail and hail dangerous clouds is investigated. Seeding was carried out in accordance with the rocket technology of hail suppression. An unseeded control cloud was matched for each seeded cloud. For this purpose, the parameter dV35 was used, which is the cloud volume with reflectivity >35 dBZ above the zero-isotherm level. A cloud was considered to be a control if at the beginning of seeding and 10 minutes earlier dV35 differs by no more than 15% from the same value of the seeded cloud. To assess seeding impact the radar and lightning characteristics of seeded and control clouds pairs were analyzed. It was found that the average, maximum and minimum values of the maximum reflectivity, the height of the upper boundary, the vertically integrated water content, the intensity of precipitation and dV35 are higher for seeded clouds and the height of the maximum reflectivity is slightly lower than the similar values of the control clouds. Seeding leads to statistically significant changes in cloud characteristics at the level p = 0.01. Seeding induces a 4.4-fold increase in the frequency of intracloud discharges, a 3.7-fold increase in the frequency of negative cloud-to-ground discharges, and an almost complete termination of positive cloud-to-ground discharges. Such significant changes in hail and hail-dangerous clouds as a result of seeding may indicate the possibility of artificial control of their lightning activity, as well as the possibility of using these changes for assessing the hail suppression efficiency.