The World Wide Lightning Location Network (WWLLN) over Spain

Abstract. A study to determine the detection efficiency and location accuracy of the Worldwide Lightning Location Network (WWLLN) over Spain is presented by comparing data with those of the Meteorological Spanish Agency (AEMET), taken as a ground truth. The WWLLN operates a planetary distributed network of stations which detect lightning signals at a planetary scale. Very high currents from lightning strokes radiate strong Very Low Frequency (VLF) signals in the band 6–22 kHz, which are detected up to 10,000 km by the WWLLN stations. Two WWLLN stations operate in the Iberian Peninsula since 2012, which are supported by other stations at distances below 4000 km. The stations in the Iberian Peninsula are at a distance of around 800 km. This is a short distance in comparison with the typical distance between WWLLN stations in other areas, which is around 5.000–15.000 km. The WWLLN stations locate the time and position of the lightning stroke detected by triangulation, similarly as Global Positioning Systems do. Distances to each station are obtained by means of the time of arrival of the signal to the corresponding stations. A lightning detection is considered as a valid one when at least five stations detect it with a time and space coincidence with AEMET data of 0.5 s and 20 km, respectively. A study of the WWLLN performance for the whole area of Spain is carried out, obtaining that the detection efficiency of WWLLN is around 38 % with a location accuracy between 2 and 3 km. The efficiency for high energy strokes is considerable higher. The results obtained for Spain are better than those obtained in previous studies in other areas of the World, which may be caused by the high density of stations in the Spanish region and its surroundings. A study for two reduced regions with different geographic features is also considered to assess the possible influence of the different typology of storms on the network features. Finally, an application of the WWLLN data for three major storms in 2020, 2021 and 2022 in the Mediterranean area of Spain demonstrates that the WWLLN is well suited for tracking the time evolution of adverse meteorological phenomena.