FORTE radio‐frequency observations of lightning strokes detected by the National Lightning Detection Network

Abstract

Abstract. This work compares simultaneous observations of lightning from two complementary systems. FORTE is a low-Earth-orbit satellite carrying radiowave and optical instruments for the study of lightning. The radio receivers aboard FORTE observe very high frequency (VHF) emissions from the air-breakdown process preceding (and sometimes accompanying) a lightning current. The National Lightning Detection Network (NLDN) is a ground-based array of sensors in the contiguous United States observing the low-frequency (LF) and very low frequency (VLF) radiation from vertical currents. Prior to the launch of FORTE in 1997, essentially no work had been done on the statistical correlations between (1) ground-based LF/VLF and (2) spaced-based VHF remote sensing of lightning. During a 6-month campaign in April-September 1998, FORTE took most of its triggered VHF data over and near the contiguous United States, and NLDN data were specially postprocessed in a loosened-criterion mode providing enhanced detection range beyond the coastline and borders of the array itself. The time history of reported events from the two systems was compared, and event pairs (each pair containing one event from FORTE, the other from NLDN) which were candidate correlations (closer than 200 ms from each other) were scrutinized to determine whether the members of a pair actually came from the same discharge process. We have found that there is a statistically significant correlation, for a subset of FORTE events. This correlation is most likely to occur for intracloud and less likely to occur for cloud-to-ground discharges. The correlated VHF and NLDN events tend to occur within +30 Us of each other, after correction for the propagation of the VHF signal to FORTE from the NLDN-geolocated stroke location. Most correlations outside of _+30 Us turn out to be merely a statistical accident. The NLDN-furnished geolocation allows the correlated FORTE-detected VHF pulses to be better interpreted. In particular, we can deduce, from the lag of the VHF groundreflection echo, the height of the VHF emission region in the storm.

Joint radio and optical observations of the most radio-powerful intracloud lightning discharges

“…The second parameter is the delay of the TIPP echo (if there is an echo), while the third is the signal-to-noise ratio (SNR) of that echo feature relative to the rms statistical noise of the autocorrelation (Jacobson et al, 1999(Jacobson et al, , 2011. In cases where the lightning has been geolocated either by the LLS or by coincidence with groundbased lightning-detection networks (see, e.g., Jacobson et al, 2000), the TIPP echo delay can be used to infer the discharge height above the reflective ground.…”

Study of oblique whistlers in the low-latitude ionosphere, jointly with the C/NOFS satellite and the World-Wide Lightning Location Network

“…Figure 14b is similar, but restricted to stroke locations within 1000 km. The baseline in such a histogram gives a measure of the level of "accidental" coincidence (Jacobson et al, 2000), so that the peak-to-baseline ratio is effectively the ratio of "real + accidental" to "accidental" coincidences, or the coincidence signal-to-noise ratio (SNR). Figure 14 shows that the SNR exceeds 8 for distance <10 000 km, and approaches 20 for distance <1000 km.…”

A Wildfire Behavior Modeling System at Los Alamos National Laboratory for Operational Applications

“…In order to develop a realistic database of fire starting points within the Los Alamos region, we adopted a dataset of lightning strike locations (Jacobson et al 2000, Smith et al 2002. These strike locations were organized by geographic coordinates and by signal strength ( Figure 5).…”