A decade of high‐latitude lightning location: Effects of the evolving location network in Finland

Abstract

The present lightning location system of the Finnish Meteorological Institute has been in operation since 1998. We present statistics from the 10‐year period 1998–2007. The main emphasis of this study is to give a comprehensive analysis of the development of the location system. Our results complement previous studies by providing 10‐year lightning statistics from high latitudes in Europe (60–70°N). The changes in the detection efficiency have also been discussed. Our results indicate that in Finland (1) the median (average) peak currents in 2007 were −11.3 (−16.0) kA and +13.3 (+20.7) kA for negative and positive flashes, (2) the percentage of positive flashes in 2007 was 17%, (3) the average multiplicity for negative (positive) flashes in 2007 was 2.1 (1.2), (4) the median semimajor axis of the 50% location error ellipse in 2007 was 600 m (for 92% of flashes it was below 5 km), and (5) the average number of sensors reporting a flash in 2007 was 6.3. The network has experienced several configuration changes, leading to a more stable and better performing system, but these technical changes have also caused significant changes in the statistics of the measured lightning data. Clearly, lightning statistics over a 10‐year period cannot be handled without considering the impact of technical changes on the detection network.