Assessing the Territory According to the Degree of Thunderstorm Danger

Introduction

This chapter presents the assessing method of thunderstorm danger on a vast, low-density populated territory, where there is a lack of monitoring tools and systems, except global lightning detection networks. In some regions of the world, especially in sparsely populated areas, thunderstorms are the main cause of wildfires. For example, in the boreal zone of North America (Johnson, 1992), in the northern part of Canada (Wierzchowski, Heathcott, & Flannigan, 2002), in the sparsely populated northern regions of Siberia, the proportion of fires caused by lightning can reach 70–90% (Kozlov, Mullayarov, & Solovev, 2009; Ivanov & Ivanova, 2010; Tarabukina & Kononova, 2018). In areas where wildfires mainly occur due to careless handling of fire by the local population, sometimes thunderstorms significantly increase the complex fire hazard situation (Ganteaume, 2013; Conedera, Cesti, Pezzatti, Zumbrunnen, & Spinedi, 2006).

The most significant cause of the outbreak of wildfires is intense dry thunderstorms, which are formed and develop most often in drought conditions. However, the passage of absolutely dry thunderstorms is quite rare and most often thunderstorm processes are accompanied by precipitation. It should be noted that fires caused by thunderstorms most often occur during air mass thunderstorms (or heat thunderstorms), which are characterized by small precipitation. With the passage of frontal thunderstorms precipitation is uneven - from its complete absence to heavy rain. It is established that even heavy rain is not able to eliminate the fire caused by lightning (Ivanov & Ivanova, 2010). The fire may be unextinguished inside the deadwood or under the canopy of trees. In good weather such a weak hidden burning can turn into a strong fire. Therefore, there is a possibility of wildfires in the five-day and ten-day intervals after the passage of thunderstorms (Kozlov et al., 2009; Ivanov & Ivanova, 2010).

Strong ground lightning discharges predominantly have a burning effect (Larjavaara, Pennanen, & Tuomi, 2005; Solovyev, Kozlov, Karimov, & Vasiliev, 2010). The greatest current strength is characteristic of positive lightning discharges (Rakov & Uman, 2003; Mullayarov, Toropov, Kozlov, & Karimov, 2009). Such discharges occur on the outskirts of thunderstorm fronts and are accompanied by weak precipitation. In defining the possible places of wildfires, it is necessary to know the conditions of a territory’s lightning hazard.

Thus, the study of the nature of the spatial-temporal distribution of lightning discharges is one of the important components in understanding the processes accompanying the occurrence of a wildfire caused by the activity of a thunderstorm discharge. The chapter will be focused on the description of ways and methods for assessing the territory according to the degree of thunderstorm danger.

On the example of the territory of the south of Siberia, the study of the spatial and temporal distribution of lightning activity is presented. It is worth noting that the territory of the south of Siberia is a mountainous country, which includes the territory of the Altai-Sayan mountainous country (ASMC) and the territory of the Republic of Buryatia. For mountainous countries poor development of road infrastructure is typical and it is in remote areas that thunderstorms are most often the main cause of wildfires. Due to the late detection and inability to use the equipment, fires cover large areas and cause significant damage. Therefore, for mountainous countries, it is important to define areas of the most susceptible to the occurrence of wildfires caused by lightning discharges (Wierzchowski et al. 2002; Conedera et al., 2006; Kozlov et al., 2009; Ivanov & Ivanova, 2010; Ganteaume, 2013; Müller & Vacik, 2017).