A performance assessment of the World Wide Lightning Location Network (WWLLN) via comparison with the Canadian Lightning Detection Network (CLDN)

摘要

The World Wide Lightning Location Network (WWLLN) uses globally-distributedVery Low Frequency (VLF) receivers in order to observe lightning around theglobe. Its objective is to locate as many global lightning strokes aspossible, with high temporal and spatial ( 10 km) accuracy. Sincedetection is done in the VLF range, signals from high peak current lightningstrokes are able to propagate up to ~10 km before being detectedby the WWLLN sensors, allowing for receiving stations to be sparsely spaced.Through a comparison with measurements made by the Canadian LightningDetection Network (CLDN) between May and August 2008 over a 4° latitudeby 4° longitude region centered on Toronto, Canada, this study foundthat WWLLN detection was most sensitive to high peak current lightningstrokes. Events were considered shared between the two networks if they fellwithin 0.5 ms of each other. Using this criterion, 19 128 WWLLN strokes(analyzed using the Stroke_B algorithm) were shared with CLDN lightningstrokes, producing a detection efficiency of 2.8%. The peak currentthreshold for WWLLN detection is found to be ~20 kA, with itsdetection efficiency increasing from 11.3% for peak currents greater than20 kA to 75.8% for peak currents greater than 120 kA. The detectionefficiency is seen to have a clear diurnal dependence, with a higherdetection efficiency at local midnight than at local noon; this isattributed to the difference in the thickness of the ionospheric D-regionbetween night and day. The mean time difference (WWLLN − CLDN) betweenshared events was −6.44 μs with a standard deviation of 35 μs, andthe mean absolute location accuracy was 7.24 km with a standard deviation of6.34 km. These results are generally consistent with previous comparisonstudies of the WWLLN with other regional networks around the world.Additional receiver stations are continuously being added to the network,acting to improve this detection efficiency.