Numerical Simulation Research on the Effect of Hail Suppression by AgI Seeding on Microphysical Process and the Charge and Discharge of Hail Cloud

Abstract

A hail process in Xunyi hail suppression experimental area of Shaanxi Province at 13:00 （Beijing Time） on 28 July 1997 was simulated by using a three-dimensional strong storm dynamic electric coupling numerical model.This paper analyzes the influence of artificial hail suppression on the concentration and temporal and spatial variation of ice particles in clouds， as well as its influence on electrification and discharge.The results show that， overall， the concentration and specific water content of ice crystals， snowflakes and graupel particles increase in the range of -40~0 ℃.AgI seeding reduces the average scale of graupel and greatly reduces the conversion ratio to hail， resulting in the reduction of specific water content and number concentration of hail.With the increase of AgI seeding dose， hail suppression effect will be better， but the rainfall will first increase and then decrease.Therefore， the seeding dose should take an appropriate value between balanced hail suppression and precipitation enhancement.AgI seeding will lead to the positive lower non-induced electrification zone appears earlier， the center is enhanced and the upper boundary is raised in the early stage， while in the late stage， the center of the negative upper non-induced electrification zone is enhanced.Therefore， the bottom sub-positive charge area was enhanced in the early stage after seeding， and the upper main positive charge area and the middle negative charge area were enhanced in the late stage.With the increase of catalytic dose， these changes became more obvious.AgI seeding has a certain inhibitory effect on ground lightning， but the cloud flash and total flash increase a little after seeding， the peak time of the first discharge and cloud flash is earlier， the discharge duration is stronger， and the lightning frequency is slightly reduced in the lightning frequent period.

Keywords

• hail cloud
• artificial hail suppression
• charge structure
• discharge type
• numerical simulation of thunderstorm clouds