This grant supports the development and use of new balloon-borne instruments to determine the electrical forces from charge carried by lightning channels inside thunderclouds. One of the instruments, an electric-field-change meter, detects the presence of ionizing waves that are not otherwise observable. Another, an electric field meter, measures the vertical profile of the electric field, which provides the energy to support the propagation of lightning. The measurements are analyzed in relation to high-resolution maps of lightning flashes obtained from a ground-based network of VHF receivers linked together by Global Positioning System (GPS) timing, called a lightning mapping array. Using the combination of balloon-borne observations, maps from the lightning array, and radar observations of storm structure, the immediate goals are to learn how lightning is initiated, how much electrical charge is required for the propagation of lightning channels inside clouds, and how lightning is related to the air motions and precipitation of thunderclouds. The long-term goal is to be able to deduce some of the properties of thunderstorms, including beneficial and damaging effects, from the characteristics of the lightning they produce.
