Voltages inside and just above thunderstorms

We estimate the voltage relative to the Earth inside thunderstorms and at c loud top from balloon soundings of electric field through convective region s and stratiform clouds. These are the first estimates we know of that give the voltage through the entire depth of storm clouds. Cloud top voltages w ere available for 13 soundings and ranged between -23 and +79 MV, with an a verage of +25 MV. The average cloud top voltage among the nine cases with p ositive values was +41 MV. These values support the Wilson [1920] hypothesi s that thunderstorms drive the global electric circuit. The average cloud t op voltage above electrified stratiform clouds was +32 MV, so these clouds may also make a substantial contribution to the global electric circuit. Wi thin clouds the voltage values ranged between -102 and +94 MV in the 15 sou ndings. The voltage difference associated with intracloud and cloud-to-grou nd lightning flashes estimated from our soundings is in the range of about 20 to 130 MV. From the voltage differences inside storms we estimate the en ergy available for weak and strong lightning flashes as approximately 10(7) and 10(10) J, respectively.