| According to the problem of how initial lightning discharges is researched based on the full lightning 3d location data and corresponding discharge waveform gained by Low-frequency E-field Detection Array(LFEDA)which is self-development by Chinese Academy of Meteorological Sciences.Researching the feature and difference of the two initial lightning discharge pulses which are narrow bipolar events and initial breakdown pulses(The first pulse of the initial breakdown pulse cluster is defined as FIBP).Simulating the transmission rule of both as the initial signal.The initial discharge process of lightning is analyzed.Specific results are as follows:The application and analysis tools of low frequency full-flash detection array location data and discharge waveform are written.lightning pulses can be classified as a lightning process,initial lightning pulses can be selected,initial pulse waveform can be displayed by using this tool.The characteristics of the lightning initial process initiated by NBE and IBP is revealed.Lightning process can be initated by both NBE and IBP.The intracloud lightning account for 14 percent,while the cloud-to-ground lightning account for 30 percent which initiated by NBE.The intracloud lightning account for 86 percent,while the cloud-to-ground lightning account for 70 percent which are initiated by IBP.As an initial NBE(INBE),it is more isolate and larger than the first pules of initial IBP(FIBP).The average time interval from INBE to subsequent first pulse is 7ms,with a mid-value of3.9ms.The amplitude ratio between INBE and the subsequent pulse is 3.5.The above values is larger than those of FIBP with the corresponding values of 0.6ms,0.2ms and 0.8.Most of the positive INBE and FIBP corresponds to a upward discharge in the initial stage while negative correspond to a downward ones.The shorter rising time for INBE also indicates a faster velocity.There are not apparent difference in rise time,half-peak width and pulse width for INBE,NBE in process and isolated NBE.It is difficult to distinguish INBE from other NBE by pulse property.A physical discharge model of two kinds of lightning discharge events NBE and IBP is established.Simulation results show that,NBE and IBP can be both regarded as the transmission line of vertical development.The current conforms to the double exponential distribution.Contrast with measured results shows that,the transprot speed of NBE is6.5×10~7m/s,while the IBP is 1.5×10~8m/s.The development scale of NBE is 494m,while the IBP is 296m.The simulative electric field waveform of INBE and FIBP is displayed with the change of transmission distance.There are obvious electrostatic field and induction field where INBE within 15km,FIBP within 10km.In the future,the radiation field is dominant.On the integrated waveform,with the increase of distance,the positive and negative amplitude ratio increases and the pulse width increases. |
