Three-dimensional lightning mapping observations as a complement to radar observations of storms

Observations of the total lightning activity inside storms can valuably complement radar as a means of sensing the location, structure, and severity of convective storms. The observations are obtained by accurately measuring the arrival times of impulsive VHF radiation signals from the lightning at a countywide network of receiving stations. The measurements can be processed to obtain 3-dimensional pictures both of individual lightning discharges and of the overall electrical activity in storms over a 150 to 200 km diameter area, and 2-dimensional observations over a 400-500 km diameter area. Mapping networks are being operated by NASA in northern Alabama and by the University of Oklahoma and National Severe Storms Laboratory in central Oklahoma and provide real-time pictures of the development of storms in these areas (see lightning.nmt.edu/oklma and www.ghcc.msfc.nasa.gov/sport/sport_lightning.html, and associated links) Of particular interest in both locations is the development of large storm systems. The lightning activity is essentially continuous in such storms and shows the location and development of the storm cores and the occurrence of convective surges in the storms. The lightning intensity is found to be a good indicator of storm intensity and severity. Characteristic lightning-free regions and lightning `holes' (or partial holes) are often observed inn conjuction with tornadoes in supercell storms. The structure and inferred polarity of the lightning activity also provide additional information on the storm nature. In summary, the mapping data provide an entirely new and intriguing way of looking at storms.