Lightning stroke clustering into cloud-to-ground lightning flashes

Abstract

Cloud-to-ground stroke data have been analysed for the years 2010-2012 for the Cata- lan region. These strokes have been grouped together into lightning ashes using a hierarchical clustering method, with two di erent approaches to the clustering radius, as the objective of the study was to evaluate di erent clustering methods. The results for the two approaches were com- pared with the results from a step-by-step method, giving us di erences of 2% and 7% in the nal number of lightning ashes. Using di erent values for the lightning ash window and lightning spa- tial radius the multiplicity values from the clustering methods results ranged from 1.6 to 2.0. These results can improve the reliability of studies where the number of lightning ashes is important such as in severe weather case studies or in climatological rainfall to lightning ratio analysis.