Earth’s Atmosphere and Its Electrical Characteristics

Abstract

Based mainly on the way in which the atmospheric temperature varies with height, Earth’s atmosphere is divided into several radial sections. The way in which the air temperature of Earth’s atmosphere varies as a function of height is depicted in Fig. 4.1. Observe that as height increases from ground level, initially the temperature decreases with height, reaches a minimum value at a certain height, and then starts to increase. The height where the temperature starts to increase again is called the tropopause. The height of the tropopause is not constant around the globe. In tropical regions, its height is approximately 12 km and in temperate regions approximately 9 km. The region below the tropopause is called the troposphere. As we will see later, all thunderstorm activity around the globe takes place in the troposphere. With increasing altitude from the tropopause the temperature starts to increase (it could also remain more or less stable over tens of kilometers), and the next inversion point where the temperature starts to decrease with height is called the stratopause. The region between the stratopause and the tropopause is called the stratosphere. This tendency for the temperature to increase with height is broken again with increasing altitude at a height known as the mesopause. The region between the mesopause and the stratopause is called the mesosphere. As we will see later, all three of these regions of the atmosphere – troposphere, stratosphere, and mesosphere – take part in activities related to lightning flashes. Indeed, it is the troposphere where thunder clouds and lightning flashes manifest themselves, but their effects are felt in both the stratosphere and the mesosphere, and these indirect effects manifest in various forms and are called upper atmospheric lightning flashes (a description of these electrical events is given in Chap. 19). But it should be understood that these are not independent events but are always related to the action of lightning flashes taking place in the troposphere. The way in which these indirect effects are manifested depends on the electrical characteristics of the atmosphere and the gas density.