Abstract
Thunderstorm activity is indirectly taken into account when using statistics on forest fires. Another way is to use the data of the lightning discharge finding sensors. This chapter proposes using the data of the World Wide Lightning Location Network (WWLLN). To assess the probability of forest fire occurrence, it is necessary to know the energy and the spatial distribution of lightning discharges. For the analysis of the data of the storm-direction-finding WWLLN, it is proposed to use clustering algorithms. For the computational experiment, the region covering the Timiryazevskiy forestry of the Tomsk region (55.93 - 56.86) on the north, (83.94 - 85.07), and the data on lightning discharges registered by the WWLLN network in this region in July 2014. The sample data were 273 lightning discharges. The results of clustering are presented, as well as the image of the silhouette index for each object, the average value of the ASW index for grouping solutions obtained using the complete, kmeans, and dbscan algorithms.
TopBackground
One of the causes of forest fires are lightning discharges. Lightning is an electrical discharge caused by separation into positive and negative charges in the clouds, which leads to a potential difference of the order of 10-100 MV [Latham & Williams, 2001]. In order to discharge is occur, the presence of water in all three phases is necessary (solid, liquid and gaseous) [Williams, 1989].
Thunderstorms are divided into intramass and frontal ones. Intra-mass thunderstorms over the continent arise as a result of local warming of air from the Earth's surface, which leads to the development in it of the ascending streams of local convection and to the formation of powerful cumulonimbus clouds. Frontal thunderstorms occur at the boundaries between warm and cold air masses [Kozlov & Mulyayarov, 2004]. Discharges may be classes of cloud-to-cloud and cloud-to-ground. Approximately 90% of the cloud-to-ground discharges are negative, and the nature of the remaining 10% of the positive discharges is not fully understood [Latham, 1991]. Discharges of the cloud-to-ground class [Ivanov, 1996] can lead to the forest fire. Energetic characteristics of the positive and negative cloud-to-ground lightning discharges are different. These differences are significant in terms of forest fuel ignition. Energy reaches the surface in one stroke as a result of the majority of positive discharges. In the same time, for the negative discharges a multi-stroke is characteristic [Uman, 1969].
Key Terms in this Chapter
Thunderstorm: An atmospheric phenomenon, in which electrical discharges occur within the clouds or between the clouds and the earth’s surface - lightning accompanied by thunder.
Lightning: An electrical spark in the atmosphere that usually occurs during a thunderstorm.
World Wide Lightning Location Network (WWLLN): An international network for registering lightning discharges on the globe. WWLLN was based at the University of Washington in 2002 and currently includes more than 70 receiving stations.
The density of Lightning Discharges: The ratio of the number of lightning discharges to the area of the site in which they are registered.
Thunderstorm focus: A region of space with an active generation of lightning.
The Republic of Buryatia: An administrative unit within the Russian Federation.
Cluster Analysis: A method of uniting groups (clusters) of objects of research according to the principle of their proximity. The object is a point of multidimensional space, where its coordinates are given by the values of several marks. The measure of proximity of objects is given in different ways, for example, the Euclidean distance.