Analysis of Lightning Field Changes Produced by Florida Thunderstorms.
Abstract
An interactive computer program has been developed to compute accurate values of lightningcaused changes in the cloud electric field (DeltaE). The DeltaE's for individual discharges in eight Florida thunderstorms have been analyzed using a nonlinear, leastsquares minimization procedure and point charge (Q) and point, dipole (P) models of the change in cloud charge. The results indicate that the temporal and spatial behavior of the Q and P model parameters are similar to those reported previously by Koshak and Krider (1989). In all storms, the high altitude Pvectors tend to point downward toward a narrow altitude band of Qsolutions that is centered at about 8 km; low altitude Pvectors tend to point upward toward the Qregion, and the Pvectors that are at the same altitude as the Qsolutions tend to be horizontal. Because there are inherent limitations in the above leastsquares analysis method and models, a new, fundamentally different approach for analyzing lightning field changes has been developed. This method finds an optimum volume charge distribution on a grid of finite dimensions and resolution. With this linear approach, we now have the ability to describe complex field change patterns subject to a variety of external constraints. We also have a framework in which a standard eigenanalysis can be used to access the general information content of data and the effects of measurement errors. Tests of the linear method with simulated lightning sources show that a centroid of the lightning charge distribution can be retrieved to within the grid resolution (2 km) when a Landweber iterative algorithm is used. Tests on three natural lightning events show that there is good agreement with previous Q and Pmodel solutions and a reasonable result for one event that could not be described with either a Q or a Pmodel.
 Publication:

Ph.D. Thesis
 Pub Date:
 January 1990
 Bibcode:
 1990PhDT.......162K
 Keywords:

 Physics: Atmospheric Science