Radar studies of formation and development of hail cores in severe convective clouds

The results of analysis of long-term radar observations of hailstorms are presented. The dynamic characteristics of formation and development of hail cores in severe convective clouds are studied. The statistical sample of radar data included 314 hail cells; for each cell the temporal distributions of measured and computed major radar parameters were constructed using the automated system of acquisition, processing, and presentation of radar data. The most informative time characteristics of hail cores’ development and the interrelation between them were identified. The natural variability of hail core volume is demonstrated. The empirical dependence of the maximum hail core volume on the maximum radar reflectivity of a hailstorm was obtained.     

A new approach to estimation of physical efficiency of active modification of intense hailstorms

A principally new criterion that takes into account a probabilistic nature of introduction of an agent into a seeding layer was used when estimating the physical efficiency of active modification. The results of the analysis of intense hailstorm modification show that the criterion adequately determines the modification success, which is confirmed by the time variation of convection cell parameters.     

Radar research of hailstorm formation and development over the central part of Northern Caucasus (Russia). Organization and main results of the regional hail suppression projects

The results of the analysis of long-term radar research of the hailstorms over the central part of the Northern Caucasus are presented. Radar observations which formed the basis of experimental material were carried out continuously from the moment of the first radar echo registration until complete dissipation of the hailstorm. The computerized system of collecting, processing and the analysis of the radar information was used. Time discretization of the radar parameters of the full spatial observation averaged 3 min. Statistical sampling of radar data included 392 hail cells, for each of which the time distributions of the radar parameters both measured and calculated using the computerized system were compiled. Distribution of the hailstorms first radar echo formation zones over the observation region was compiled. Areas with the maximum frequency of the hailstorms first radar echo formation were defined. The hailstorm trajectories were analyzed. Four main types of hail cell trajectories were selected, which included 86 % of the supercells and 64 % of the long-lived multicells. The dynamic parameters of the hail core formation and development were analyzed. The hail storm characteristics of the Northern Caucasus are compared to the hail storms of Mendoza, Argentina, and Alberta, Canada. The bases of the organization of regional hail suppression services which use the rocket technology of cloud seeding are presented. The results of the cloud seeding operations during recent years are shown.     

Radar studies of the distribution of the formation zones of the first radar echo of hail clouds

The results of studying the regions of hail-cell formation in the North Caucasus are considered. The optimal range of the underlying surface heights for their generation is determined based on an analysis of 392 hail cells. It is shown that the majority of hail cells are formed in the zone where the heights of the underlying surface vary from 900 to 2400 m. The most favorable conditions for the formation of hail clouds are recorded in the northern slopes of the Skalistyi (Rocky) ridge. This region accumulates the main maxima of the frequency of first radar echo recording. The second group of the frequency maxima is located over the Pastbishchnyi (Pasturable) and the Lesistyi (Woody) ridges. The generalized scheme for the region under study is constructed of three zones of generation of the first radar echo of the hail cells. It is shown that approximately 70% of hail clouds are formed over submontane and mountainous regions in the central North Caucasus (zones 2 and 3). The directions of motion of hail cells are quantified for each identified zone.     

Radar research of hailstorm formation and development over the central part of Northern Caucasus (Russia). Organization and main results of the regional hail suppression projects

The results of the analysis of long-term radar research of the hailstorms over the central part of the Northern Caucasus are presented. Radar observations which formed the basis of experimental material were carried out continuously from the moment of the first radar echo registration until complete dissipation of the hailstorm. The computerized system of collecting, processing and the analysis of the radar information was used. Time discretization of the radar parameters of the full spatial observation averaged 3 min. Statistical sampling of radar data included 392 hail cells, for each of which the time distributions of the radar parameters both measured and calculated using the computerized system were compiled. Distribution of the hailstorms first radar echo formation zones over the observation region was compiled. Areas with the maximum frequency of the hailstorms first radar echo formation were defined. The hailstorm trajectories were analyzed. Four main types of hail cell trajectories were selected, which included 86 % of the supercells and 64 % of the long-lived multicells. The dynamic parameters of the hail core formation and development were analyzed. The hail storm characteristics of the Northern Caucasus are compared to the hail storms of Mendoza, Argentina, and Alberta, Canada. The bases of the organization of regional hail suppression services which use the rocket technology of cloud seeding are presented. The results of the cloud seeding operations during recent years are shown.

     

The use of hail cloud jet model in operative practice of hail protection

The hail cloud parameters are computed on the basis of jet convection model using the real atmospheric stratification. The analysis of these computations shows the opportunity to use the jet convection model for the operative forecast of hailstorms and their intensity.