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 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

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 mb or kilopascals. Pressure is the weight of air above sea level (I kilogram per 1cm 2).

Air pressure numbers on weather maps are called ‘isobars’ One half the atmosphere is below 5.6 km

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