National Lightning Detection Network (NLDN) performance in southern Arizona, Texas, and Oklahoma in 2003–2004

Abstract

[1] Four field campaigns were conducted in southern Arizona (AZ) and in northern Texas and southern Oklahoma (TX-OK) in 2003 and 2004 to evaluate the performance of the U.S. National Lightning Detection Network TM (NLDN) in detecting cloud-to-ground (CG) lightning after an upgrade in 2002 and 2003. The 2-year average flash detection efficiency (DE) in AZ was 93% (1024/1097), and the measured (first plus subsequent) stroke DE was 76% (2746/3620). The corresponding values in TX-OK were 92% (338/367) and 86% (755/882), respectively. After correcting for the time resolution of the video camera (16.7 ms), we estimate that the actual NLDN stroke DE and video multiplicities were about 68% and 3.71 in AZ and 77% and 2.80 in TX-OK. The average DE for negative first strokes (92%) was larger than the measured DE for subsequent strokes that produced a new ground contact (81%) and the DE for subsequent strokes that remained in a preexisting channel (67%). The primary cause of the NLDN missing strokes was that the peak of the radiated electromagnetic field was below the NLDN detection threshold. The average estimated peak current (I p ) of negative first strokes and the average multiplicity of negative flashes varied from storm to storm and between the two regions, but this variability did not affect the DE as long as the recording sessions had more than 60 flashes. By analyzing the NLDN locations of subsequent strokes that remained in the same channel as the first stroke we infer that the median random position error of the NLDN was 424 m in AZ and 282 m in TX-OK. An evaluation of the classification of lightning type by the NLDN (i.e., CG stroke versus cloud pulse) showed that 1.4-7% (6/420 to 6/86) of the positive NLDN reports with an I p 10 kA in TX-OK were produced by CG strokes; 4.7-26% (5/106 to 5/19) of the positive reports with 10 kA < I p 20 kA were CGs; and 67-95% (30/45 to 30/32) of the reports with I p ! +20 kA were CG strokes. Some 50-87% (52/104 to 52/60) of the negative, single-stroke NLDN reports in AZ and TX-OK with jI p j 10 kA were produced by CG flashes. Both the upper and lower bounds in these classification studies have observational biases.

The European lightning location system EUCLID – Part 1: Performance analysis and validation

“…As a result, the estimated LA of an LLS based on lightning strikes to towers is expected to be somewhat better than that for natural lightning. On the other hand, the LLS location error determined from video data of strokes in the same channel is an upper limit because the return stroke channel is not always seen all the way down to the ground strike point of each return stroke (Biagi et al, 2007). Keeping in mind those specific limitations of tower measurements and VFRS recordings, the agreement between LA determined from GBT data and VFRS data in Austria is almost perfect.…”

“…Due to the reason that almost no positive flashes with multiple strokes in the same channel exist, the LA is determined with negative flashes only. The method to estimate the LLS LA, based on multi-stroke flashes, is described in Schulz et al (2012) and Biagi et al (2007). As mentioned in Schulz et al (2012) this method does not show any systematical location error.…”

Analysis of lightning-induced forest fires in Austria

“…The detection efficiency since 1999 on cloud to ground flashes is 98 %. This makes it one of the best-performing LLS worldwide (ALDIS 2009;Anderson 2002;Biagi et al 2007;Castedo-Dorado et al 2011;Diendorfer 2007;Outcalt 2008;Podur et al 2003). The first detection sensor was put into operation in 1991, and archived lightning data are available since 1993.…”

“…Because ALDIS detects around 98 % of all CG flashes in Austria (Diendorfer 2007), it was assumed that lightning could not have been the cause of the forest fire, if there were no flashes detected within the relevant time period. Single positive flashes under 10 kA were excluded from the analysis too, even if they were the nearest events, because studies have shown that these flashes are mostly (more than 90 %) CC and not CG lightnings (Biagi et al 2007;Diendorfer 2007;Hall and Brown 2006). Additionally, the probability for each lightning flash was estimated by the location accuracy of a specific flash (error ellipse).…”

“…Castedo-Dorado et al 2011;Conedera et al 2006;Hall and Brown 2006). The declaration "lightning fire" is taken as confidential.…”