The Establishment And Simulation Of A 3D High-resolution Multi-uplink Pilot Stochastic Model

In order to deepen the understanding of the phenomenon of multiple upward leaders initiated from tall structures in attachment process,a new model is presented,in which the initiation and development module of multiple upward leaders are implanted in the existing three-dimensional(3D)stochastic parameterization of leader attachment process,using electric field parallel computing technology to improve the simulation efficiency.The new model has been applied to simulate real CG lightning in Guangzhou actual building groups and is compared with the observation results of statistical data and leader morphological characteristics in this paper,which is proved reasonable in some extent.In order to carry out the research of initiation mechanism,based on the newly established multiple upward leaders model,a comparative experiment is set up to discuss the influence of ground building and downward leader parameters on the inception of multiple upward leaders.Both observation and model work have found that the downward leader has the probability to strike the subsequent leader initiating from the low building.In order to explain it,this paper designs a group of sensitivity experiments on the influence of altitude intercept on the inception and attachment of multiple upward leaders.The main research conclusions are as follows:(1)Compared with the single leader model,the 3D high resolution multiple upward leaders stochastic model established in this paper is more reasonable and can simulate the lightning channel similar to the single leader model when the downward leader intensity is weak.It can also simulate the multiple upward leaders when the downward leader intensity is strong.(2)The simulation results of lightning attachment process of Pearl River New Town in Guangzhou are consistent with the observed results.The results show that the highest tower can protect a certain area of buildings nearby and attract more distant downward leader branches,the higher the height of the building,the more obvious this effect is.The inception of multiple upward leaders and the strike point of last jump are influenced by the distribution,height of high structures and the initial position of the downward leader.(3)The influence of each parameter on initiation of multiple leaders is as follows: the increase of single high building height will make the number of initiating multiple leaders decline until it reaches the critical height of initiating only one upward leader.The range of the critical height increases as the distance between the single tall building and the center position of building group increases.The downward leader intensity can affect the number of upward leaders.The stronger the lightning,the easier it is to trigger more leaders.When the lightning is weak and the position is biased,the upward leader will not even be triggered from the building group.The initial position of the downward leader and the interval between buildings mainly affects the initiation position of the upward leaders.(4)On the study of the altitude intercept on the initiation and attachment of the upward leaders,it is concluded that there are two critical height differences in the high and low buildings,which represent that the low building no longer give priority to initiating upward leaders and when the low building can no longer initiate upward leaders.(5)The statistical results show that when the height difference of the high and low building is between two critical height differences,the downward leader often strikes the subsequent leaders initiated from the low building.When the height difference reaches the second critical height,the event mainly occurs in the same high building.Whether this phenomenon occurs on the same building is affected by the height difference of two buildings,and the main reason is the different initial position and development patterns of the downward leaders.