Exploring first and second-order spatio-temporal structures of lightning strike impacts in the French Alps using heavy subsampling

Abstract This applied spatial statistics paper deals with a dataset of cloud-to-ground lightning strike impacts in the French Alps over the period 2011–2021 (approximately 1.4 million of events) modelled by a spatio-temporal point process. We explore first and higher-order structure for this point pattern and address the questions of homogeneity of the intensity function, first-order separability and dependence between events. Due to the nature of the dataset (very inhomogeneous in space and time) and the large amount of data, most of the nonparametric methods and statistical tests we consider lead to numerical problems or exceed clusters timeout. We suggest different subsampling strategies strongly reducing the number of events to overcome these difficulties and show how they can be used to draw conclusions on the initial point pattern.