Measurements of atmospheric electric field made below two thunderstorms show that all lightning discharges occurring in the dissipating stage of a thunderstorm occur at almost the same value of the predischarge electric field at the ground surface. The observation is explained on the basis of the shielding of the electric fields generated by the positive charge in the downdrafts by the negative charge in the screening layers formed around them in the subcloud layer. Our observations suggest that in the dissipating stage of the thunderstorm, the charge generating mechanisms in cloud have ceased to operate and the charge being transported from the upper to lower regions of cloud by downdrafts is the only in-cloud process affecting the surface electric field and/or enhancing the electric field stress in and below the cloud base to cause yet another lightning discharge.
Volume 128 | Issue 8
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