Analysis of lightning field changes during active Florida thunderstorms

Abstract

A computer algorithm has been developed to derive accurate values of lightning‐caused changes in cloud electric fields under active storm conditions. This algorithm has been applied to data obtained from a network of ground‐based electric field mills at the NASA Kennedy Space Center and the U.S. Air Force Cape Canaveral Air Force Station during portions of two storms. The resulting field changes have been analyzed using a least squares optimization procedure and point‐charge (Q) and point‐dipole (P) models. The results indicate that the values and time variations of the Q‐model parameters under active storm conditions are similar to those reported previously for small storms (Maier and Krider, 1986) when the computations are done with the same analysis criteria and comparable biases. The parameters of P solutions seem to vary with time within the storm interval and from storm to storm. The P vectors at low altitudes all tend to point upward, and those at high altitudes almost always point downward. When a P solution is located in the altitude range corresponding to Q altitudes, the direction of P tends to be horizontal. Since Q solutions typically describe cloud‐to‐ground lightning and P solutions describe cloud discharges (Maier and Krider, 1986), the altitude dependence of the P vectors is consistent with the classic thundercloud charge model that has an excess negative charge at altitudes corresponding to the Q altitudes.