INITIAL COMPARISON OF LIGHTNING MAPPING WITH OPERATIONAL TIME-OF-ARRIVAL AND INTERFEROMETRIC SYSTEMS

The mapping of lightning radiation sources produced by the operational Time-of-Arrival National Aeronautics and Space Administration/Lightni ng Detection and Ranging (NASA/LDAR) system is compared with that of t he Interferometric French Office National D'Etudes et de Recherches Ae rospatiales (ONERA-3D) system. The comparison comprises lightning acti vity in three Florida storms and also individual flashes in one of the se storms. Although limited in scope, the comparison and analysis show a significant difference in the representation of lighting radiation by each mapping system. During the duration of a flash, the LDAR data show a continuity in time and a three-dimensional structure of radiati on sources. The ONERA-3D radiation source data are more intermittent i n time and have a more two-dimensional structure. The distinction betw een the radiation sources mapped by the two systems is also reflected in the difference between their propagation speeds, 10(4)-10(5) m s(-1 ), estimated by the LDAR system, and 10(7)-10(8) m s(-1), estimated by the ONERA-3D system. We infer that this difference occurs because mos t of the radiation sources mapped with LDAR are associated with virgin breakdown processes typical of slowly propagating negative leaders. O n the other hand, most of the radiation sources mapped with ONERA-3D a re produced by fast intermittent negative breakdown processes typical of dart leaders and K changes as they traverse the previously ionized channels. Thus each operational system may emphasize different stages of the lightning flash, but neither appears to map the entire flash.