Analysis Of Characteristics For Lightning Activity And Tornadic Supercell

Based on the WRF(Weather Research and Forecasting)model incorporated non-inductive and inductive charge separation and discharge parameterization,a supercell involving server tornadoes,strong hail and frequent lightning activity was simulated.The relationship of server tornadoes,hail and lightning were analyzed,and the reasons were further explored by perspective of microphysics,dynamics and electricity.The observations show that the ground flashes are relatively frequent,and dominated by-CG(negative Cloud-to-Ground)before the occurrence of hail.The lightning flashes increase rapidly and quickly peaked about 20 minutes before hail production;the lightning flashes were momentarily weakened and the polarity of ground flash have reversed,which from negative polarity to positive polarity after the hail production.The lightning jump occurred and rapidly peaked,and the tornado was under the formation and had not yet touched the ground.The lightning frequency has been weakening during the development of the tornado.No ground flashes have occurred in the mesocy clone area and the peaked time intensity of the mesocyclone lags behind in the peaked time for lightning flashes frequency about 15 minutes.The simulated results demonstrated that:(1)The content and size of particles have quickly increased and the height of particles have descended for updraft sudden strengthen leading to hydrometers have steadily collision-coalescence increases.The wind for vertical direction have tilt resulting in amounts of hydrometers into Flank Fear Downdraft(FFD).The negative charge region at lower have formed after graupel/hail-ice/snow rebounding collision charge separation and the positive charge region were enhanced in the action of non-inductive and inductive together at mid-level.Frequently discharge have occurred between main positive charge zone at mid-level and negative charge zone at low-level resulting in positive ground flashes rates have jumped.The collision between particles were much more intense after hail production,and the content of graupel and hail have constantly increased and the height have sostenuto descended.The charge structure was dominated by inverted tri-pole charge structure.Therefore,the positive ground flashes have dominated after hail falling.(2)Seldom ground flashes occurred in mesocyclone area because of rebounding collision separation was above 8 km so that hardly discharged to ground resulting from intensity of updraft was powerful resulting in particles rise higher.The inclination of the wind brings a large number of particles into FFD region,and the particles were with collide violently,resulting in frequent lightning discharges.The downdraft was strengthened within FFD,leading to downdraft produces vorticity below the rotate updraft,and under the influence of cyclostrophic low pressure perturbation in the center of the helical updraft,which provides an upward directed force to pull the downdraft air upward to make the connection with the rotating updraft,leading to the intensity of mesocyclone at mid-level was further enhanced.Therefore,the intensity of mesocyclone was peaked lagging the peak for frequency of ground flashes about 15 minutes.The updraft and downdraft were both weaken after the tornado strongest.The cloud water content was lower and the temperature was higher at low-level.The graupel charged positively non-inductive rebounding collision charge separation consisting of small positive charge region,which restrain the occurrence of positive cloud-to-ground.(3)The occurrence of hail causes the FFD(Front Flank Downdraft)and RFD(Rear Flank Downdraft)subsidence beginning to increase.Under the interaction of the updraft within the main updraft region and the RFD subsidence,the middle cyclone intensity is also increasing.It is more conducive to the occurrence of tornadoes,and the continued increase in subsidence flow of FFD causes the charged particles' height to begin to decrease,but the collision and electrification process between particles becomes weaker,and the electrification and discharge activities begin to weaken.