Cloud-to-ground lightning characteristics of warm season Mesoscale Convection Systems in the Central United States: 1992-1993

Abstract

This study provides a detailed analysis of cloud-to-aphics. ground (CG) lightning flashes within individual Mesoscale Convective Systems (MCSs) that occurred in the Central United States during May-August of 1992 and 1993. Analysis of the CG lightning flashes provided a climatology of the CG lightning characteristics within MCSS. Specifically, the total number of bashes per storm system flash rate, percentage positive, first stroke peak current, and flash multiplicity were examined. Also, by comparing the storm systems of 1992 vs.1993, it was determined whether the CG lightning characteristics of the flood producing storm systems of 1993 were vastly different than the preceding year. Results from the climatology of the CG lightning characteristics showed that the total number of flashes per storm system (V = 74.4 %), percentage positive (V = 71.1 %), and flash rate (V = 63.5 %) values showed relatively high variance from storm system to storm system. In contrast, the positive multiplicity (V = 10.9 %), negative multiplicity (V = 10.5 %), and (mean and median) negative peak current (V = 9.2 % and V = 8.8 %) values did not exhibit as much of a discrepancy between the 67 storm systems. The (mean and median) positive peak current (V = 20.6 % and V = that the positive peak current was higher than the negative peak current within the majority of the individual MCSS and that the maximum negative peak currents were generally observed in the second half of the life cycle of the storm systems. The storm systems of 1993 averaged a higher number of flashes per storm system (2 5,000 flashes more) and a higher overall flash rate (B 300 flashes/ltr more), while averaging nearly the same duration (12.0 hrs) as the storm systems of 1992 (11.4 hrs). This comparison between the two years studied seemed to indicate that the storm systems of 1993 were more electrically active than the storm systems of 1992. However, closer examination showed that the apparent differences between the total number of flashes per storm system and flash rate yielded a low level of statistical significance (p = 0.46) due to the aforementioned high variations in these CG characteristics.