Laboratory studies of the graupel nuclei formation and the processes of their further growth in a liquid droplet medium

The article presents a set of equipment for studying the growth of graupel nuclei and the growth of graupel particles. It was established in the work that the growth parameters as mass, the rate of mass growth have extreme values from –5 °C to –12 °C. It was found that at the initial stage of hail formation, two growth modes are observed: first, the growth of ice particles occurs due to the diffusion of water vapor; second, the growth of ice particles occurs as a result of crystal aggregation. The calculated values of the density of ice formed during the diffusion of water vapor vary from 0.9 to 0.97 g/cm3, in the second case from 0.2 to 0.6 g/cm3. A significant increase in the growth rate of hail occurs during the translational-rotational movement of the air flow in the wind tunnel. The article shows that with an increase in water content, the growth rate of hailstones increases. When the water content reaches approximately one gram per cubic meter there is a sharp decrease in the growth rate. With a further increase in the water content, the growth rate increases. The sharp decrease in the growth rate is most likely due to the fact that at a water level of about one gram per cubic meter, the nuclei are saturated with moisture and the ice density increases, and this leads to a decrease in the rate of hail growth.