Discuss the mechanism by means of which the atmosphere is able to maintain its heat-balance. Is the atmosphere getting progressively hotter, and if so, why? (200 Words)
The source of heat for our planet is Sun. Energy from the sun is transferred through the space and through the earth’s atmosphere to the earth’s surface. There are three ways heat is transferred into and through the atmosphere:- conduction, convection and advection.
- The atmosphere is largely transparent to the incoming solar radiation before reaching the earth, whereas it is opaque to outgoing radiations which reflects part of it back to the earth.
- Some amount of insolation received at the top of the atmosphere is reflected back to the space and the remaining part are absorbed by the atmosphere and the earth surface.
- The earth after being heated up, often transmits the heat to the atmospheric layers.
- The air in contact with the earth’s surface gets heated slowly and also heats the upper layers in contact with the lower layers. This process is called conduction. This process is important in heating the lower layer of atmosphere.
- The air on heating rises vertically in the form of currents and transmits heat to the upper layers. This process of vertical heating is called convection and is confined only to the troposphere.
- The transfer of heat through horizontal movement of air is called advection. It is a very important phenomenon which is responsible for the day-night duration of everyday weather in middle latitudes.
- The long wave radiation from earth is absorbed by the atmospheric gases such as CO2 and other Green-house gases which heats up the atmosphere. The atmosphere in turn re-radiates and transmits heat in all directions towards the space and earth.
Thus the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth’s surface and in the atmosphere. But trapping of long wave radiation by the increased concentration of Green-house gases leads to gradual heating of earth’s atmosphere and surface, a process known as green-house warming. The beginning of industrial revolution, burning of fossil fuels, deforestation etc. contributes greatly for adding billions of tons of heat trapping green-house gases in the atmosphere.