Three-dimensional lightning mapping observations in storms

A GPS-based system for mapping both individual lightning discharges and the total lightning activity inside storms has been developed and used to study storms in Oklahoma, New Mexico, and most recently during the STEPS 2000 campaign in northwestern Kansas and eastern Colorado. The system produces detailed three dimensional images of the lightning activity by accurately measuring the time of arrival of impulsive radiation events over a countywide network of measurement stations. Observations have been obtained of the initial and complete sequences of lightning in relatively small New Mexico storms, and of the large and extremely active electrical storms of the western great plains. Of particular interest in the latter are the discovery of lightning-free regions, or lightning `holes', in tornadic and supercell storms, that appear to be characteristic of very strong updrafts in the storms. In two cases, tornadoes formed on the western edge of the lightning holes. Also discovered is the occurrence of frequent, short duration (sub-millisecond) discharge events within overshooting convective tops in large storms. The discharges rise up above other lightning in the storm to altitudes approaching 16 to 19 km and indicate the presence of strong convective surges in the storms. Many of the mapping observations have been obtained in conjunction with dual-polarization or conventional radar observations of the storms.