The atmosphere of Earth is a layer of gases surrounding the planetEarth that is retained by Earth’s gravity. The atmosphere protects lifeon Earth by absorbing ultraviolet solar radiation, warming thesurface through heat retention (greenhouse effect), and reducingtemperature extremes between day and night.
Composition of airAir is the name given to atmosphere usedin breathing and photosynthesis.
The Atmosphere ______ The temperature in the atmosphere ______ varies depending on the different ______ layer we are in. ______
The Troposphere (I)• It is the lowest level ofearth’s atmosphere wherethe right mixture of oxygenand nitrogen works tosupport life.• Here, living things are also free from the radiation showerswhich flow down through most of the earth’s atmosphere.• Compared to the rest of the atmosphere, the troposphere is a tinylayer, extending at most 16km up from the earth’s surface. Withinthis small layer almost all of our weather is created.
The Troposphere (II)• Generally, as altitude increases, temperature decreases steadily.But the earths topography—mountain ranges and plateaus—cancause some lower regions in the troposphere to experiencetemperature inversions.• Towards the top of thetroposphere temperaturesfall to an average low of -57 ºC and wind speedsincrease significantly,making the top of thetroposphere an extremelycold and windy place.
The Stratosphere (I)• The gradual change from thetroposphere to the stratospherebegins at approximately 11kmhigh. The temperature in thelower stratosphere is extremelystable and cold at -57 ºC.• There are strong winds. Highcirrus clouds sometimes formin the lower stratosphere, butfor the most part there are nosignificant weather patterns inthe stratosphere.
The Stratosphere (II)• From the middle of the stratosphere and up, the temperaturepattern undergoes a sudden change, sharply increasing withheight. Much of this temperature change is due to increasinglevels of ozone concentration which absorbs ultravioletradiation. • The temperature can reach 18 ºC in the upper stratosphere near an altitude of 40km high.
The Mesosphere• 40km above the earth’s surface marks the transition to themesosphere. In this layer, temperature once again begins to fallas altitude increases, to temperatures as low as -143 ºC near itstop, 81km above the earth. • Such extreme cold allows the formation of so-called noctilucent clouds, made of ice crystals clinging to dust particles.
The Thermosphere• It directly above the mesosphere and directly below theexosphere. Within this layer, ultraviolet radiation causesionization.• Thermospheric temperatures increase with altitude due toabsorption of highly energetic solar radiation by the small amountof residual oxygen still present. Temperatures can rise to 2,000°C.• Radiation causes thescattered air particles inthis layer to becomecharged electricallyenabling radio waves tobounce off and bereceived beyond thehorizon.
The Exosphere• The exosphere is the uppermostlayer of the atmosphere.• In the exosphere, an upwardtravelling molecule moving fastenough to attain escape velocitycan escape to space; if it ismoving below escape velocity itwill be prevented from escapingby gravity.
The greenhouse effect is a process by which radiation from the surface of the Earth is absorbed by atmospheric gases, and is re-radiated in all directions.Since part of this re-radiation is back towards the surface, energy istransferred to the surface and the lower atmosphere. As a result, thetemperature there is higher than it would be if direct heating by solarradiation were the only warming mechanism.
Earth is the third planet fromthe Sun, and the densest and fifth-largest of the eight planets inthe Solar System. It is also thelargest of the Solar Systems fourterrestrial planets. It is sometimesreferred to as the world, the BluePlanet, or by its Latin name, Terra.