Abstract:

Lightning is the main source of natural fire, and lightning fire and other types of forest fires together constitute the global forest fire system. It is generally believed that lightning fire, as a natural fire source, has nothing to do with human beings and is different from man-made fire sources, but in fact, human activities have inextricable links with the occurrence of lightning fire. Since 2019, due to the severe impact of COVID-19 lockdowns, non-essential activities and mobility have decreased, which has led to a significant decrease in pollutant concentrations and lightning. In this paper, we linked the lightning fire with modernization process of human beings, the expansion of habitation, the change of underlying surface, the development of prediction technology and firefighting technology, and the laws and regulations of the country, to explore the impact of human activities on the occurrences of lightning and the forest lightning fire. Lightning is the fire source of the three elements in lightning fire occurrence, the lightning that can cause lightning fire is mainly cloud-to-ground lightning. The human activities in recent decades have profoundly affected the content of aerosols in environment. Aerosols are the main factors affecting lightning, and the large amount of pollution aerosols emitted from urban areas, soot aerosols emitted from biomass combustion and urban heat island effect have all increased the probability of lightning occurrence. The average annual ground lightning density of different land cover types is obviously different, and the construction land has the highest average annual ground lightning density. Intense lightning in forest areas has a higher density and slope. Most of the forests are located in high altitude areas, which is consistent with previous studies showing high lightning frequency in high altitude areas. The lightning in forests is intenser, steeper and more destructive, so forest areas are prone to lightning strikes. Lightning has the characteristic of selective discharge, that is, it will discharge into some special areas, which are also known as lightning selection areas, such as the place groundwater is exposed to the ground, where different conductive soils are connected, and where there are underground metal mines, such as copper and iron mines, and underground lake and water reservoir areas. Lightning strikes are caused by changes in soil conductivity caused by human activities such as mining waste rock sites, reservoir construction on mountain tops, and power transmission lines in mountainous areas. At the same time, due to the abundant trees in the mountainous area, it is also important to avoid the resulting lightning fire. With the development of lightning monitoring technology, a lightning location monitoring system has been established in some areas of China. Especially in 2021, the National Forestry and Grassland Administration launched the "Enlisting and Leading" emergency science and technology project of forest lightning fire prevention and control, and the project team has constructed a lightning fire sensing system in the Daxing'anling region with three-dimensional lightning full-wave detection network as the main body, covering the forest area of the Daxing'anling forest region, which can accurately locate the location of cloud-to-ground lightning in real time, improve the monitoring and warning ability of lightning fires, and improve the efficiency of lightning fire discovery. National laws and regulations indirectly affect lightning fires by affecting forest cover and climate change. This paper is expected to provide reference for the occurrence, prevention and control of forest lightning fire in the future, and provide a basis for the formulation of corresponding policies.

Key words: lightning, lightning fire, human activities, modernization process, monitoring and early warning