Electric-field changes of lightning observed in thunderstorms

During the Summer and Fall of 1998 we launched five balloon-borne instrumen ts into thunderstorms to observe changes in the vertical component of elect ric field caused by lightning. Four of these were for measurement of field change only. The fifth was part of a larger package that included a gamma r adiation detector and a GPS receiver on board. We have processed electric-h eld-change data from two of these flights. We discuss examples of field cha nges observed at altitude and compare them with data from the National Ligh tning Detection Network (NLDN) for cloud-to-ground lightning flashes that w ere coincident in time. Limits on time resolution and timing accuracy preve nt unambiguous identification of the lightning processes that caused the fi eld changes. It appears that they may have been caused by charge movements relatively near the instruments as compared with the ground-strike location of coincident flashes.