Simulation study of discharge processes in thunderstorm

The discharge characteristics in thunderstorm have been calculated by using a numerical cloud model. The results indicate that discharge processes occur when simulated thunderstorm developed at the stage of 30—45 min and initial locations of discharge mainly dlstributes between 4.4—4.8 km and 6.4—6.8 km above the ground (corresponding to ambient temperature of - 10°C and - 25°C). In simulated thunderstorm with a tripole electric structure, 10% of discharges occur between upper positiie charge area and middle negative charge area and propagate upwards (from middle negative charge area to upper positive charge area); while, 90% of discharges occur between lower positive charge area and middle negative charge area and propagate downwards (from negative charge area to lower positive charge area). There is a positive correlation between updraft and discharge. The occurrence of discharge process needs hydrometer with a specified concentration and size in cloud (corresponding to ⩾5 mm/h for precipitation on the ground). The maximum value of precipitation lags the peak of discharge number by a period of about several minutes. The discharge and its variation in thunderstorm are an important factor for monitoring and forecasting thunderstorm.