Airborne measurement of atmospheric potential gradient

Grounded-rotor induction-type electric field meters are mounted horizontally at the wing tips and vertically at the bottom of the fuselage of a P4Y airplane for the airborne measurement of the fair weather atmospheric potential gradient. The measurement has been corrected for the electric field distortion due to the aircraft itself by comparing observed values of potential gradient and conductivity at the earth's surface and at altitude during low-altitude flights over a portable ground station. A typical altitude distribution of potential gradient observed during clear weather at 67° north latitude is integrated to obtain a value of atmospheric potential at a 6-km altitude of 220 kv relative to the earth's surface.