Numerical Simulation of Evolution and Electric Structureof the Cumulonimbus Cloud in Northwestern Russia

This paper continues the research started in [4] that investigates the thundercloud with hail observed over Saint Petersburg on July 22, 2017. The results of numerical simulation of the cumulonimbus cloud using a small-dimensional model are presented. The spatiotemporal variations in the updraft velocity, liquid water content, ice water content, volume charge density, electric field strength, and other parameters are studied. Two cases are simulated and intercompared: without and with the heterogeneous cloud droplet freezing. It is shown that the formation of precipitation including hail occurs more intensively in the second case. Special attention is paid to the simulation of cloud electric structure, which was performed in combination with the modeling of its dynamics and microstructure. It is demonstrated that the most powerful cloud electrification processes occur due to the interaction between cloud and precipitation particles (hailstone–ice crystal, melting hailstone–cloud droplet, raindrop–cloud droplet). The dynamics of the cloud electric structure at different life stages is modeled.