Performance Characteristic Improvements of the U.S. National Lightning Detection Network

Updates made in 2012 to the U.S. National Lightning Detection Network® (NLDN®) has led to performance characteristics improvements. Deployment of Vaisala's LS7001 sensors continued in 2012 replacing the older generation IMPACT sensors. The LS7001 employs the latest digital sensor technology along with improved embedded software with enhanced features. Digital processing improves the sensitivity of the sensor to low amplitude lightning-generated signals. Digital filtering of local noise sources allows better signal-to-noise ratio along with flexibility in site-selection. These have led to enhanced detection of cloud and cloud-to-ground lightning. The LS7001 sensors use onset corrections, which accurately determine the arrival time of electromagnetic waveforms from lightning events at a sensor. This reduces the timing error and improves the accuracy with which lightning events can be geolocated. Additional factors such as propagation across uneven terrain, varying ground conductivity, and the accurate speed of electromagnetic waves propagating over ground are also being accounted for. This has led to an improvement in the median location accuracy (given by the length of the semi-major axis of the 50% error ellipse) of the NLDN from about 300 m to about 150 m in the interior of the network. These performance characteristics continue to be validated by triggered lightning, tower, and camera studies.