A study of the characteristics of thunderstorm cessation at the NASA Kennedy Space Center

Abstract

A lightning summary was developed for a 100xlOO kilometer area centered at the NASA Kennedy Space Center. Spatial and temporal patterns, and first stroke peak currents were analyzed from 1986-1995, Three thunderstorms were chosen due to their proximity to the Kennedy Space Center (KSC) and examined for their end of storm characteristics. Radar echoes at the-100C and-200C temperature heights were associated with cloud-to-ground (CG) lightning strike locations from the National Lightning Detection Network, Electric fields were also examined during the same time frame for any correlations,A pattern was observed for the spatial distribution of CG lightning, An inland maximum in ground flash density was observed during the summer months for both negative and positive flashes. The summer months had the lowest percentage positive flashes (2.5%) while the maximum value occurred during the winter (11,4%), Although thunderstorms can occur at any time during the day, the diurnal distribution of lightning flashes showed that the afternoon (2000 UTC) was the time of maximum lightning activity. From a time history of radar echoes, it was found that a 45 dBZ echo, last detected at the-IOOC temperature height, may be a good indicator of the end of lightning activity, The observed lag times between this lightning termination signature and the end of all CG lightning flashes was 30 min for all three thunderstorms, Analysis of these storms using the 40 dBZ reflectivity level at the-100C temperature height, as well as, both reflectivity levels (40-45 dBZ) at the-200C temperature height did not yield as successful results, The electric field mill analysis did not provide any conclusive results in identifying the end of CG lightning activity. However, electric fields did remain high even after the termination of all lightning flashes, indicating the high potential for triggered lightning.