An evaluation of the Worldwide Lightning Location Network (WWLLN) using the National Lightning Detection Network (NLDN) as ground truth

A performance assessment of the Worldwide Lightning Location Network (WWLLN) is presented using the National Lightning Detection Network (NLDN) as ground truth, over unprecedented time and spatial scales. The study spans 3 years, from 5 April 2006 to 31 March 2009, throughout the contiguous United States. The capabilities of the network are shown to improve greatly from the first to the third year of the study, with an overall detection efficiency of cloud-to-ground flashes increasing from 3.88% in 2006 -2007 to 10.30% in 2008-2009. The WWLLN cloud-to-ground detection efficiency is found to be strongly dependent on peak current and polarity, attaining values larger than 10% (35%) for currents stronger than +/- 35 kA (-130 kA) and values less than 2% for currents between 0 and -10 kA. The location accuracy is found to have a northward and westward bias, with average location errors of 4.03 km in the north-south and 4.98 km in the east-west directions, respectively. The WWLLN is shown to have strong limitations in capturing the diurnal cycle, missing both the timing of the maximum and minimum lightning activity (around 1600 and 0900 LT, respectively), and the amplitude of the cycle as well. It is found that in 3 h intervals, the number of flashes in the WWLLN has some proportionality to the number of flashes in the NLDN, suggesting that the WWLLN has strong potential for meteorological applications.