I I T M Presentation On ATMOSPHERE Presented BY :- Ankit Sinha Arpan Shukla Satyendra yadav Shalendra S. Sengar Yogesh Bhadauria IITM,EC 2nd

CONTENTS Introduction Composition of Atmosphere Structure of Atmosphere Ozone layer Present Scenario Conclusion

ATMOSPHERE The atmosphere is the thin layer of air that surrounds the earth.The gravitational force of the earth holds the atmosphere around it.It protect us from the harmful rays and scorching heat of sun.It consist of number of gases,dust and water vapour.

Composition of ATMOSPHERE There are many different types of gases in the atmosphere They include nitrogen oxygen, argon, carbon dioxide and other noble gases The gas that is most abundant is nitrogen

Structure of ATMOSPHERE

Structure of ATMOSPHERE (cont.) There are 5 layers in the atmosphere as shown in fig. They are the:- Troposphere Stratosphere Mesosphere Thermosphere Exosphere Each layer has its different composition of gases.

TROPOSPHERE This is the layer closest to the Earth.Weather occurs in this layer. Live occurs in the troposphere.The height of the troposphere varies from the Equator to the poles (17-18 km).It is highest at the equator. The zone of the troposphere where the temperature remains fairly constant is the tropopause.The tropopause divides the troposphere from the stratosphere. The air pressure at the top of the troposphere is only 10% of that at sea level (0.1 atmospheres).

Stratosphere The stratosphere extends from the tropopause to an altitude of about 50 km.In the lower stratosphere, the temperature is around –60 degrees C.Here very strong eastward winds blow horizontally around the Earth.The jet streams here reach speeds of 320 km per hour. The thin ozone layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun.

Mesosphere This is the third layer of the atmosphere.It lies above the stratosphere.It extends upto height of 80 km.Above the mesosphere, the temperature begins to decrease to –100 degrees C.The upper region is the coldest.If watervapor is present thin clouds of ice form.The mesosphere protects the Earth from meteoroids.When they reach the mesosphere, they burn up from the friction of rubbing against the particles of gas. The mesopause at an altitude of 80–90 km, separates the mesosphere from the thermosphere.

Thermosphere The thermosphere begins above the mesosphere at a height of about 80 km.The air is very thin.The density of the atmosphere and the air pressure are one ten-millionth of what they are at the Earth’s surface. Thermosphere means heat-sphere.The temperatures reach 2000 degrees C.because this layer absorbs the ultraviolet radiation from space and convert it into heat.This layer helps in radio transmission.Within this layer UV rays causes ionisation.

Exosphere The upper thermosphere is called the exosphere. The layers are to scale. From Earth's surface to the top of the stratosphere (50km) is just under 1% of Earth's radius.The exosphere extends from 550 km above the surface for thousands of km.The air is very thin.Artificial satellites orbit in the exosphere. In the exosphere, an upward travelling molecule can escape to space if it is moving fast enough to attain escape velocity.

Structure of ATMOSPHERE

Ozone Layer Ozone forms when electricity passes through the stratosphere.Most of the ozone in the atmosphere is found between 16km and 60 km about the surface of the Earth.Ozone shields the Earth from ultraviolet radiation. This layer absorbs 93-99% UV rays.

How is ozone formed? Ozone is formed naturally in the upper stratosphere by short wavelength ultraviolet radiation. Wavelengths less than ~240 nanometers are absorbed by oxygen molecules (O2), which dissociate to give O atoms. The O atoms combine with other oxygen molecules to make ozone: O2 + uv (light) O + O (wavelength < 240 nm) O + O2  O3

How is the ozone layer being depleted? Ozone is produced naturally in the stratosphere. But this "good" ozone is gradually being destroyed by man-made chemicals referred to as ozone-depleting substances (ODS), including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, methyl bromide, carbon tetrachloride, and methyl chloroform. These substances were formerly used and sometimes still are used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants. Now let us see how ozone layer being depleted……………

How is the ozone layer being depleted?(CONT.)

Present scenerio Graph representing yearwise incresement of composition of Methane in atmosphere Graph representing yearwise incresement of composition of CO2 in atmosphere

CONCLUSION

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