Short Duration Discharges Located by NMIMT's Lightning Mapping Array

While analyzing the LMA data, a distinct subset of lightning discharges has been observed. These events are short in duration, lasting less than 80 microseconds and often the LMA only records a single point. Actual source points are difficult to distinguish from random system noise; however, three categories of short duration discharges have been identified as real lightning events. The first category is the isolated event, where single point discharges are occurring in a region of the storm where other lightning has occurred. They do not appear to be associated with any of the larger, more substantial discharges within the storm. These short duration events are often localized, and in some instances are the only discharge in given area for several seconds. A preliminary comparison of these isolated discharges in one storm on June 29th, 2000, to the wind-field data from the radar synthesis, shows that most of them are occurring on the edges of the updrafts. These are also the same type of discharges that have been seen in the convective surges higher up in the storm that indicate severe weather. Another type of short duration discharge is the precursor event, which can occur up to half a second before an intra-cloud discharge. They are located in the same area as the initial points of the following discharge. This is different from the isolated events which are scattered spatially. The last category of short duration discharges is the high source power event, which have powers ranging from 100 kW to 52MW in the 60-66 MHz passband. These high power events have been seen as both isolated and precursor events. What makes them different is that they are significantly higher in power than 99% of the other located LMA sources, which range from 1W to 10 kW. Some of these events have been recorded by fast antenna and from the sferic waveform they have been identified as positive bi-polars. Analysis of these short duration flashes is an ongoing attempt to better understand the total lightning picture.