Nitrogen and oxygen are two gases which make up the bulk of the atmosphere. Carbon dioxide, helium, ozone, argon and hydrogen are found in lesser quantities. Plants need nitrogen for their survival. They cannot take nitrogen directly from the air. Bacteria, that live in the soil and roots of some plants take nitrogen from the air and change its form so that plants can use it.
Oxygen is the second most plentiful gas in the air. Green plants produce oxygen during photosynthesis.
Carbon dioxide is another important gas. Green plants use carbon dioxide to make their food and release oxygen. Burning of fuels add billions of tons of carbon dioxide into the atmosphere each year. As a result, the increased volume of carbon dioxide is affecting the earth’s weather and climate.
Our atmosphere is divided into five layers starting from the earth’s surface. These are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
Troposphere: Its average height is 13 km. The air we breathe exists here. Almost all the weather phenomena like rainfall, fog and hailstorm occur in this layer.
Stratosphere: Above the troposphere lies the stratosphere. It extends up to a height of 50 km. This layer is almost free from clouds and associated weather phenomenon, making conditions most ideal for flying aero planes. One important feature of stratosphere is that it contains a layer of ozone gas.
Mesosphere: It lies above the stratosphere. It extends up to the height of 80 km. Meteorites burn up in this layer on entering from the space.
Thermosphere: In thermosphere temperature rises very rapidly with increasing height. Ionosphere is a part of this layer. It extends between 80 to 400 km. This layer helps in radio transmission. In fact, radio waves transmitted from the earth are reflected back to the earth by this layer.
Exosphere: The upper most layer of the atmosphere is known as exosphere. This layer has very thin air. Light gases like helium and hydrogen float into the space from here.
The average weather condition of a place for a longer period of time represents the climate of a place.
It is the incoming solar energy intercepted by the earth. The amount of insolation decreases from the equator towards the poles. Therefore, the temperature decreases in the same manner.
Air builds a great force on our bodies. However, we don’t feel it because it presses us from all directions and also our body exerts a counter pressure.
The air pressure is highest at sea level and decrease with height.
The movement of air from high pressure area to low pressure areas is called wind. Winds can be divided into three types/
Moisture in the air is known as humidity. When the air is full of water vapor we call it a humid day. As the air gets warmer, its capacity to hold the water vapor increases and so it becomes more and more humid. When the water vapor rises, it starts cooling. The water vapor condenses causing formation of droplets of water. Clouds are just masses of such water droplets. When these droplets of water become too heavy to float in air, then they come down as precipitation.
Jet planes flying in the sky leave a white trail behind them. The moisture from their engines condenses. We see trails of this condensed moisture for some time when there is no air movement disturb it.
When trees on hill sides are cut, rainwater flows down the bare mountains and can cause flooding of ow lying areas. There are three types of rainfall: the convectional rainfall, the orographic rainfall and the cyclonic rainfall.