Simulation Of Triggered Upward Flashes Process

This paper is mainly based on a stochastic parameterization scheme for the upward lightning under the background of an existing two-dimensional thundercloud charge/discharge model.Through multiple groups of experiments with two-dimensional high resolution,quantitative analyzing the beneficial effect of the cloud lightning process to trigger generated upward lightning.The main conclusions are as follows:(1)The results show that the intracloud-lightning-triggered upward flashes occur in the typical three pole charge structure.A large number of hetero polar charges are implanted in the main positive and negative charge regions after preceding intracloud flashes(IC),while the bottom secondary positive charge area is almost unaffected.After the intracloud flash,the negative potential near ground space(0-3km)turn to positive potential and negative potential well moved or disappeared,the ground is potential trap center;At the same time,the original air strong electric field is destroyed,the whole space electric field is reduced,the upper part of the main role,positive the main negative charge region of ground electric field is weakened.Because of the positive charge region remained relatively intact,the ground electric field significantly enhanced electric field polarity reversed,the values of electric field enhancement,the upward lightning triggered.(2)We proposed two hypotheses of how upward flash trigger.One is that the upward positive leader triggered another tower-initiated flash with a negative upward leader,the other is that the upward negative leader triggered another tower-initiated flash with a positive upward leader.The former occur in the typical three pole charge structure,the latter occur in the four pole charge structure.The previous upward lightning triggered a upward lightning process,corresponding to the cloud space charge layer distribution has a certain degree of tilt,this kind of charge layer tilt may caused by strong wind or the fast moving of cloud layer distribution and migration above of the building.(3)In comparison with upward flashes initiated simultaneously from two high-object separated,we find that the previous upward lightning make the near ground charge area relatively enhance the role of the ground,making the reversal and enhancement of the electric field near the ground.The location distance of the two lightning starting points is mainly in the range of 0.4 to 4.4km,and the location difference of the two upward lightning starting point is more than 80%.The location distance is between 1.2 and 4.0km,and starting point location distance between 1.6 and 3.2km is more than 50%.