The Atmosphere

The Atmosphere

• The atmosphere is essential to life as it provides oxygen for animals, carbon dioxide for plants, it stabilizes the differences in temperatures between the polar and tropical regions, traps solar energy, recycles water and shields life from ultra violet radiation

Composition• Live at the bottom of

an ocean of air• Held to earth by

weight/gravity• Five layers• Nitrogen 78%• Oxygen 21%• Argon 1%• Water vapour 0 .4%• ozone

Exosphere

Thermosphere

Mesosphere

Troposphere

Stratosphere

http://www.rcn27.dial.pipex.com/cloudsrus/atmosphere.html#layers

Everest 8000m

Composition

• Water vapour ; important in the formation of clouds

• Ozone; important as absorbs harmful ultra -violet radiation from the sun

• Carbon Dioxide; absorbs radiant energy and reflects energy

Structure

Structure

• Layers that vary according to composition and temperature

• Troposphere is where nearly all water vapour, clouds and weather occur

• Important as water vapour absorbs heat, provides moisture and acts as an insulating blanket

• Temperature ; decreases with altitude• 6.4 C/1000m (ELR) or (the environmental lapse rate)

• Pressure: also decreases with altitude. Standard sea level pressure is 1013.2mb or 101.325 kilopascals. Pressure is the weight of air above sea level (I kilogram per 1cm2).

• http://kids.earth.nasa.gov/archive/air_pressure/

• Air pressure numbers on weather maps are called ‘isobars’

• One half the atmosphere is below 5.6 km• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/prs/def.rxml

Temperature and the Atmosphere

• Insolation from the sun drives everything

• Earth sun relationship causes unequal heating of the surface– Rotation– Revolution– Tilt

Heat Distribution

Energy Budget

• Earth sun relationship causes unequal heating of the earth’s surface where the equatorial region receive more than the polar regions

• From year to year incoming radiation equals outgoing heat.

• This input and energy output is responsible for the earth’s overall temperature

• Change one, you change the other (1991 Mt. Pinatubo) or add another blanket to your bed!

• About 2/3 of the solar radiation that reaches our planet is absorbed

• 1/3 is reflected and has little effect on our temperatures

• Of the incoming solar radiation the atmosphere absorbs 18% but reflects and scatters 26%.

• Of the remaining 56% that reaches the earth’s surface, 50% is absorbed and 6% reflected.

• The fact that so much is absorbed by land and vegetation is one idication that the atmosphere is actually heated by the earth not the sun.

Physical Processes: how the lower atmosphere is heated

• Radiation• Convection• Conduction• Evaporation• Condensation• Albedo• Absorption