A classification of Texas thunderstorms according to their cloud-to-ground lightning characteristics during spring 1993

Abstract

The National Lightning Detection Network detected more than 800 000 cloud-to-ground lightning flashes from 119 storm systems which affected Texas during April-June 1993. This study attempted to characterize these flashes over the entire three-month period, then classify the storms according to their lightning characteristics, relative to their type, geographical location, and maximum echo height. Examination of the flashes over the entire period found that the highest ground flash densities within the study region (26.50-34.5" N, 102'-930 W) were in southeastern Texas. The flashes lowering negative charge to ground had a mean multiplicity of 2.91 strokes and median first-return stroke peak current of 32.1 kiloamperes (kA). Six percent of the flashes were positive; the positive flashes exhibited a mean multiplicity of 1.43 and a median peak current of 36.6 kA. Relating the data to storm type revealed that frontal storm lightning was 2-3 times more positive than observed in airmass storms. Negative lightning in airmass storms had slightly higher mean multiplicities and peak currents than in frontal storms, while frontal storms had higher positive flash multiplicities and peak current values. Analysis by storm location showed that inland storm lightning flashes were more than twice as positive as those in coastal storms, but coastal storms had lower multiplicities and higher peak currents (both polarities) than observed in inland storms. Comparison of lightning characteristics to maximum echo height found a positive correlation between flash rates and echo heights, a negative correlation between percent positive rates and echo heights, a positive correlation between negative flash multiplicities and echo heights, and a negative correlation between positive Flash peak currents and echo heights. Negative flash peak currents remained relatively constant with increasing echo heights.