Evaluation of a long-range lightning detection network with receivers in Europe and Africa

This study focuses on the performance evaluation of the experimental long-range lightning detection network Zeus, with receivers located in Europe and Africa. The evaluation is carried out in terms of locating error and detection performance. Zeus´ receivers record the radio noise (sferics) emitted by cloud-to-ground lightning discharges in the very low frequency (bandwidth between 5 and 15 kHz). The lightning location is retrieved by means of the arrival time difference (ATD) triangulation technique. The presented study includes evaluation of the system´s locating error and detection performance over the African continent, equatorial/mid-Atlantic, the Caribbean, and northern South America. This dataset is validated over a period extending from July through October 2004. The Lightning Imaging Sensor onboard NASA´s Tropical Rainfall Measuring Mission satellite is used as the validation source. The analysis shows that the number of receivers as well as their relative location (relative position of the flash-event to the network´s receivers) plays a key role in the retrieval error magnitude. Median error values within the network´s periphery are found to be approximately 20 km, while outside the periphery significantly larger (∼130 km). Simulation of chi-square values, implemented from the ATD algorithm, shows an adequate agreement between theoretical error-related computations and the network´s retrievals. In terms of detection performance, the Zeus system is also validated over the same area/period. The chief observation is that the detection performance is likewise dependent on the number of receivers used by the system rather than their relative location.