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24 September 1983, Volume 2 Issue 3   
  • A CALCULATION OF THE MECHANISM OF THE ELECTRIFICATION BY POLARIZED PRECIPITATION IN THUNDERSTORM
  • Yan Muhong;Ge Zhengmo
  • 1983 Vol. 2 (3): 26-39. 
  • Abstract ( ) PDF (954KB) ( )
  • A numerical model relating to time with the mechanism of the electrification by polarized precipitation is employed(in this paper) to simulate the growth process of the electric field in thunderstorm and hailstorm. Assuming hydrometeores are of Marshall-Palmer distribution, the integrally separated probability and the cosine of the coalescence-angle are reasonably adopted in the caleulation in accordance with List's experimental records. It is shown from calculations that the charging rate due to the collision between hailstones and icd crystals is the highest, the electric field which is large enough to trigger lightning can be produced within about 250-750 seconds after the hailfall rate reaches 2-26mm/hour and its maximum may even grow up to 7000v/cm, the charging rate by the collision between rain drops and cloud droplets is weaker,the electric field of about 4000v/cm, however, would also appear if the charging time is long enough.The critical rainfall rate which may induce sufficient electric field to trigger lightning is 3mm/hour.This result is coincident with the observations.The eletrification by the collision between hailstones and cloud drop- lets may produce high charging rate when high concentration of droplets exists in clouds.Charging rates with great differences may happen depending upon different concentrations of droplets and under the condition of low concentration, lightning would not be stimulated even if the rainfall rate is high.This coincides also with the data of observations. As the practical maximum of electric field, about 4000v/cm, is formed in cloud, the hydrometeors may still keep falling with large speed instead of suspensing.The suppression effects of the force of the electric field on the growth of the electric field and the reversion-current effects of small ice crystals can be neglected.It is found from the calculation that the charge amount may reach about -100--400pc for single hail-particles(rad-ius 2-3mm)and-3--10pc for raindrops(radius 0.8mm).All these are similar to the data from aircraft measurements. In addition, the time of forming maximum of electric field may vary depending upon the initial state of cloud which has little effect on the electric field value, however.