Review status: this preprint is currently under review for the journal NHESS.
Global ground strike point characteristics in negative downward
lightning flashes – part 2: Algorithm validation
Dieter R. Poelman1,Wolfgang Schulz2,Stephane Pedeboy3,Leandro Z. S. Campos4,Michihiro Matsui5,Dustin Hill6,Marcelo Saba7,and Hugh Hunt8Dieter R. Poelman et al.Dieter R. Poelman1,Wolfgang Schulz2,Stephane Pedeboy3,Leandro Z. S. Campos4,Michihiro Matsui5,Dustin Hill6,Marcelo Saba7,and Hugh Hunt8
1Royal Meteorological Institute, Brussels, Belgium
2Austrian Lightning Detection and Information System (ALDIS), Vienna, Austria
3Météorage, Pau, France
4Campos Scientific Computing
5Franklin Japan Corporation, Sagamihara 212-0212, Japan
6Scientific Lightning Solutions LLC (SLS), Titusville, Florida, USA
7National Institute for Space Research, INPE, São José dos Campos, Brazil
8The Johannesburg Lightning Research Laboratory, School of Electrical and Information Engineering, University of Witwatersrand Johannesburg, Johannesburg, South Africa
1Royal Meteorological Institute, Brussels, Belgium
2Austrian Lightning Detection and Information System (ALDIS), Vienna, Austria
3Météorage, Pau, France
4Campos Scientific Computing
5Franklin Japan Corporation, Sagamihara 212-0212, Japan
6Scientific Lightning Solutions LLC (SLS), Titusville, Florida, USA
7National Institute for Space Research, INPE, São José dos Campos, Brazil
8The Johannesburg Lightning Research Laboratory, School of Electrical and Information Engineering, University of Witwatersrand Johannesburg, Johannesburg, South Africa
Received: 11 Jan 2021 – Accepted for review: 09 Feb 2021 – Discussion started: 11 Feb 2021
Abstract. At present the lightning flash density is a key input parameter to assess the risk of occurrence of a lightning strike in a particular region of interest. Since it is known that flashes tend to have more than one ground termination point on average, the use of ground strike point densities as opposed to flash densities is more appropriate. Lightning location systems (LLSs) do not directly provide ground strike point densities. However, ingesting their observations into an algorithm that groups strokes in respective ground strike points results in the sought after density value. The aim of this study is to assess the ability of three distinct ground strike point algorithms to correctly determine the observed ground-truth strike points. The output of the algorithms is tested against a large set of ground-truth observations taken from different regions around the world, including Austria, Brazil, France, Spain, South Africa and the United States of America. These observations are linked to the observations made by local LLSs in order to retrieve the necessary parameters of each lightning discharge and serves as inputs for the algorithms. It follows that all three of the algorithms perform well, with success rates up to about 90 % to retrieve the correct type of the strokes in the flash, i.e., whether the stroke creates a new termination point or follows a pre-existing channel. The most important factor that influences the algorithms' performance is the accuracy by which the strokes are located by the LLS. Additionally, it is shown that the strokes' peak current plays an important role, whereby strokes with a larger absolute peak current have a higher probability of being correctly classified compared to the weaker strokes.
The lightning flash density is a key input parameter to assess the risk of occurrence of a lightning strike. Flashes tend to have more than one ground termination point on average, therefore the use of ground strike point densities is more appropriate. The aim of this study is to assess the ability of three distinct ground strike point algorithms to correctly determine the observed ground-truth strike points.
The lightning flash density is a key input parameter to assess the risk of occurrence of a...