The Atmosphere Composition, Structure and Temperature

Weather The state of the atmosphere at a particular place for a short period of time Changes hourly, daily, and seasonally

Climate A generalization of the weather conditions over a long period of time

Qualities Measured Regularly Air temperature Humidity Type and amount of cloudiness Type and amount of precipitation Air pressure Speed and direction of the wind

Composition of the Atmosphere Major Components –78% nitrogen –21 % oxygen –Almost 1% argon –Carbon dioxide and other gases

Composition of the Atmosphere Variable Components –Water Vapor –Dust –Ozone Pollution in the lower atmosphere Layer in the stratosphere that absorbs UV rays

Height and Structure of the Atmosphere Pressure Changes –Height—the closer to Earth, the more pressure

Height and Structure of the Atmosphere Atmosphere divided according to temperature –Troposphere Layer in which we live Turbulent weather Temperature decreases with altitude Outer boundary—tropopause—about 12 kilometers high

Height and Structure of the Atmosphere –Stratosphere Temperature stays relatively stable to a height of about 20 km Temp begins a gradual increase until it reaches the stratopause, about 50 km Ozone is concentrated in the stratosphere

Height and Structure of the Atmosphere –Mesosphere Temps decrease with height until the mesopause, approximately 80 km above the Earth Temperature approaches –90°C

Height and Structure of the Atmosphere –Thermosphere No well-defined upper limit Temperatures of individual atoms and molecules reach 1000°C, but the gases are so far apart, the collective heat is insignificant

Height and Structure of the Atmosphere

Earth-Sun Relationships Rotation –Earth spinning on its axis –Circle of illumination— the line separating the dark half of Earth from the lighted half

Earth-Sun Relationships Revolution –Movement of the Earth around the sun –Earth travels more than 107,000 km per hour

Earth-Sun Relationships Seasons –The lower the angle of the sun, the more spread out and less intense is the solar radiation –Also determines the amount of atmosphere the sun’s rays must penetrate

Heat Transfer Conduction –Heat transfer by touch—by molecular activity Convection –Transfer of heat by liquids or gases moving from one place to another Radiation –Transfer of heat by electromagnetic waves –Empty space

Solar Radiation Scattering –Gases and dust in the atmosphere –About 30% of the solar energy reaching the outer atmosphere is scattered back into space –Some solar energy is scattered in the atmosphere

Solar Radiation Albedo –Amount of radiation that is reflected by the Earth’s surface

Solar Radiation Absorption –Nitrogen is a poor absorber –Oxygen absorbs most of the shorter UV radiation high in the atmosphere –Ozone absorbs most of the remaining UV rays in the stratosphere –Water vapor absorbs most of the solar radiation within the atmosphere –No gases are effective at absorbing visible light

Greenhouse Effect About 50% of solar energy that strikes the top of the atmosphere reaches Earth’s surface Earth is heated from the ground up because of radiation hitting the surface Radiation hits the Earth; some bounces back and hits particles in the atmosphere which then bounces it back to the Earth