Performance Analysis of the North American Lightning Detection Network Using Cn Tower Lightning Data

The North American Lightning Detection Network (NALDN) is a commercial lightning detection network composed of the U.S. National Lightning Detection Network (NLDN) and the Canadian Lightning Detection Network (CLDN). The NALDN was developed to provide lightning information by accurately detecting and locating most cloud-to-ground (CG) lightning strokes and a small fraction of discharges produced by cloud flashes. The NALDN allows lightning activity to be monitored in real-time for use in the protection of North American forests, for forensic applications such as in the electric power and insurance industries, and for a broad range of applications in weather nowcasting and climatology. The U.S. NLDN is owned by Vaisala Inc., while the CLDN is owned by Environment Canada. The CLDN and NLDN are completely interconnected, with all data processing being performed by Vaisala Inc. at the Network Control Center in Tucson, Arizona. From 2001 to 2003, the NLDN underwent an upgrade, creating a great need for the verification of its performance (Cramer et al. [2004]). Verification of NALDN performance is difficult due to the lack of definitive ground truth data. Before and after the recent NLDN upgrade, evaluations using digital video recording systems were performed by the University of Arizona (Kehoe and Krider [2004] and Parker and Krider [2003]). The University of Florida's International Center for Lightning Research and Testing (ICLRT) at Camp Blanding used rocket-triggered lightning to provide ground truth data (Jerauld et al. [2005]). According to Cramer et al. (2004), media and eyewitness reports of lightning strikes have also been used to verify network performance. The CN Tower is one of the best sites in the world to study tall structure lightning. Since the instrumented Tower lies on the border of the CLDN and the NLDN, it provides an excellent opportunity to evaluate the performance characteristics of the NALDN in the Toronto area. Because of the close proximity of the CN Tower to the U.S. border, two out of the three closest lightning detection sensors to the CN Tower are actually upgraded NLDN sensors. This paper presents a comprehensive evaluation of the NALDN performance characteristics in the Toronto area. The data from CN Tower lightning strikes acquired over the summer of 2005 are used to evaluate NALDN performance characteristics such as: flash detection efficiency, stroke detection efficiency, absolute location error, peak current estimation error, and location accuracy model error (50%, 90% and 99% error ellipse).