The Earth’s weather and climate: The Earth’s atmosphere has four distinct layers
The layer of atmosphere most distant from the Earth is the thermosphere, which begins approximately 80 km in altitude. It is also the hottest layer; “thermo” being Greek for heat. The temperatures in the thermosphere increase with altitude due to the absorption of intense solar radiation by the limited amount of remaining molecular oxygen.
The source of this heat is through bombardment of solar particles carried on the solar wind that do not reach deeper into the atmosphere.
The mesosphere extends from 50 to 80 km in altitude with very sparse atmosphere, accounting for only about 0.1 per cent of the mass of the atmosphere as a whole. Temperatures decline within the mesosphere as altitude rises, containing the coldest temperatures within the Earth’s atmosphere. At its upper boundary, the mesopause, average temperatures are near -110°C in the summer and -60°C in the winter.
The stratosphere extends from approximately 10-12 km to around 50 km above the Earth’s surface.
The air temperature remains relatively constant up to an altitude of 25 km, and then increases gradually having a stabilizing effect on atmospheric conditions.
The stratosphere contains nearly 90 per cent of the atmospheric ozone, which plays a major role in regulating temperatures as solar energy is converted to kinetic energy when the ozone molecules absorb ultraviolet radiation, resulting in the heating of the stratosphere.
The troposphere is the layer closest to the Earth’s surface, containing more than 80 per cent of total atmospheric mass – composed of 78 per cent nitrogen, 21 per cent oxygen, other trace gases, water droplets, dust, and other particles.
The troposphere is where most weather occurs; the circulation of air in intensive vertical movements results in the formation of clouds, while horizontal movements results in wind. Both temperature and water vapour content decrease rapidly as altitude increases within the troposphere nearly 99 per cent of atmospheric water vapour is contained within this layer, which plays a major role in regulating air temperature as it absorbs solar energy and thermal radiation from the planet’s surface.