Electrical structure in two thunderstorm anvil clouds

Two electric field soundings through thunderstorm anvil clouds show similar charge structures: negatively charged screening layers on the top and bottom surfaces, a layer of positive charge in the interior, and one or two layers of zero charge. Both anvil clouds were strongly electrified: the peak magnitudes of the electric field in the two storms were 70 and 90 kV/m, respectively. The nonzero layers had charge densities comparable to those found in the cores of thunderstorms, ranging in magnitude from 0.4 to 2.7 nC/m3. Layers varied in thickness from 300 to 2000 m. The positive charge probably originated in the main positive charge region normally found at high altitudes in the core of thunderclouds. Transporting positive charge from the storm core to the anvil may influence the ratio of intracloud to cloud-to-ground lightning flashes and the rate of generation of charge in the core. The negatively charged layers probably were screening layers, resulting from the discontinuity in the electrical conductivity at the cloud boundaries. The lower negative screening layer appeared to be carried toward the storm core by winds below and at the lower anvil boundary.