Feedback Effect Of Electric Field Upon Microphysical Process,Dynamical Development And Electric Activity Within Thunderstorms

In order to get a more particular vision of the feedback effect from electric field generated by electric activity upon dynamic development,microphysical process and subsequent charge activity within thunderstorms,the 3D dynamics-electrification coupled numerical cloud model can be used when the electric field effect?EFE?has been respectively introduced in thermodynamic equation and falling velocities for different hydrometeors.An inland moderate hailstorm's ground sounding data was chosen(Xunyi city of Shaanxi province at 1 o'clock p.m.on Jul.28^th,1997),the main differences from whether considering EFE were compared and discussed as following.?1?Under the EFE calculated circumstance,due to the weak charge activity form beginning,the updraft and downdraft speed,movement and production rates of hydrometeors remain same.However,with the accumulation of hydrometeors and enhancement of charge activity,the differences appear and last over 30 minutes till the decay stage.The accumulated feedback effect along with this total period cannot be neglected.?2?The change of falling velocity account directly for EFE.After electric field coupled,the peak velocities for raindrop,hail and ice crystal totally increase,while there are both increase and decrease for graupel's peak velocity.Electric field forces particles'grid-scale mass weighted instantaneous speeds change a lot,but it is more obvious among small-size hydrometeors,hail's instant velocity is the most susceptible comparatively because the instant speed difference of hail is nearly close to its peak falling velocity.Due to hydrometeors'falling velocity adjustment,particles'main production rates change accordingly.The rates for graupel and hail decrease little,while the rates for raindrop and ice crystal increase on the contrary,those sharp rate differences are more obvious among particle's collision process.?3?EFE broaden average spectral distribution of different particles to some degree at the height where particles get peak water contents,this arouse large-size solid particles'concentration and restrain the moderate-size's,which founds a favorable measure advantage.Total solid and liquid precipitation intensities in different cases vary little,the difference generates from precipitation appearing till the end of thundercloud,remain 2 orders smaller than that in EFE neglected case.Though the difference is not remarkable,EFE helps to put off the solid precipitation and appear the obvious periods of rising and falling tendency in mature stage.?4?EFE enhances updraft and downdraft speed,the difference peaks 1 order smaller.EFE helps condensation and evaporation intensify,deposition and sublimation shrink,increases space water vapor and latent heating,and prepares certain internal energy for thundercloud further development.Due to the synchronous change among thermodynamic field and dynamic field,positive disturbance potential temperature and updraft speed,EFE enlarges the strength of center positive potential temperature,widens its influence scope,but this influence barely touch the core spot of convective center.?5?EFE makes space charge structure and vertical electric field stay synchronized variation by contrast,the increase of decrease trend in charge structure positively correspond with the same variation of vertical electric field namely.EFE partly enhances non-inductive electrification intensity,modulates inductive electrification region,which also correspond to the variation of charge structure.EFE makes the lightning amounts nearly double,lightning generates earlier and lasts longer,the moment of high lightning frequency delays.In all,EFE promotes subsequent electrification and discharge activity within thunderstorms.