Three‐dimensional charge structure of a mountain thunderstorm

Abstract

Lightning charge transport is analyzed for a thunderstorm which occurred on 18 August 2004 near Langmuir Laboratory in New Mexico. The analysis employs wide band measurements of the electric field by a balloon‐borne electric field sonde or Esonde, simultaneous Lightning Mapping Array measurements of VHF pulses emitted during lightning breakdown, and Next Generation Weather Radar data. The thunderstorm was composed of two principal updrafts. In the stronger updraft the positively charged particles reached altitudes up to 14 km, and in the weaker updraft the positive particles reached 11 km altitude. The negatively charged particles generated in the updraft appeared to reach altitudes up to 10 km in the strong updraft and 8 km in the weaker updraft. Just outside the updrafts the positive and negative particles drop sharply; thereafter, they drop down at a nearly linear rate, between 1 and 2 km in altitude per 10 km in horizontal distance. Initially, as the updraft developed, most charge was transported by updraft flashes; later, after about 15 to 20 min, extensive flashes were predominant. Most cloud‐to‐ground (CG) flashes transported negative charge from outside the updraft at 6 km altitude down to ground; however, some strokes of a CG reached into a higher negative charge region closer to the updraft. Nearly 6 times as much charge was transported by intracloud (IC) flashes when compared to CG flashes. The ratio of the average charge transport for an IC flash to the average charge transport for a CG flash was 1.6, while the average generator current associated with the combined updrafts was 2.3 amperes for 40 min.