CHAPTER 18INVISIBLE BLANKET

THE EARTH’S ATMOSPHERE

ATMOSPHEREShields us against ultra violet rays,

bombardment of meteors, meteorites, and other objects from outer space.

Gases in the atmosphere is essential to life. It supplies the oxygen and carbon dioxide needed by living things.

As an insulator, it prevents extreme temperature.

LAYERS OF THE ATMOSPHERE1. TROPOSPHERE2. STRATOSPHERE3. MESOSPHERE4. THERMOSPHERE /IONOSPHERE 5. EXOSPHERE

TROPOSPHEREWe live in the troposphere.It extends about 14 to 16 km from the earth’s surface.Air is densest.Most of the water vapor in the atmosphere is found in

this layer.Clouds, weather and storm occur here.

JET STREAM – the topmost part of the troposphere which has fast-moving river of air. It was discovered by WW II pilots.

TROPOPAUSE – boundary between the troposphere and stratosphere

STRATOSPHEREIt is about 50km above the earth.Very little water vapor is present in this layer.Air flows in horizontal direction.Pilots fly their aircraft here to take advantage of

the horizontal wind and to void the weather in the troposphere.

No clouds in this layer.OZONE LAYER ( O3) is found in the topmost part

of the stratosphere making this layer warm; protects us against ulta violet rays.

MESOSPHEREExtends to about 90 km above the earth.In this layer temperature decreases with

height.Coldest region of the atmosphere.Most meteors from space burn in this layer

THERMOSPHEREThe topmost part of the atmosphere Temperature can go as high as 1 7270CIn here, the sun’s radiation strips off some of

the electrons from the gases present in this region making them electrically charged or ionized.

This layer reflects long electromagnetic wave back to earth making radio communication possible.

Aurora occurs (display of colors )- ions glow in diff. colors

EXOSPHEREStarts at the top of the thermosphere and

continues until it merges with interplanetary gases or space.

Hydrogen and helium are the prime components and are only present at extremely low densities.

ENERGY SOURCE OF THE ATMOSPHEREA significant aspect of the atmosphere is

motion. HEAT - kinetic energy in a moving molecule.

Heat travels from hotter substance to cooler substance. It is a measure of energy.

TEMPERATURE – refers to the degree of hotness.

SUN – major source of energy on earth.

METHODS OF HEAT TRANSFER1. CONDUCTION – is the transfer of heat

from one substance to another by direct contact.

2 CONVECTION - is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it. Convection above a hot surface occurs because hot air expands, becomes less dense, and rises (see Ideal Gas Law). Hot water is likewise less dense than cold water and rises, causing convection currents which transport energy.

3. RADIATION – heat energy travel in empty space. It travels in the form of waves given off by hot objects. This is the reason why a heavily lighted room is warmer than a room with a single bulb.