Unit 6: The Atmosphere

Atmosphere Composition Different today than long time ago! How? 2 main gases make up 99% of the atmosphere Nitrogen—78% Oxygen 21% Other gases in atmosphere Carbon Dioxide—small amount/important Water Vapor—amount varies also important

Atmosphere Structure Pressure decreases as you rise in the atmosphere Air molecules rapidly thin!

Heat Transfer Radiation Conduction Convection Heat that travels through empty space Conduction Heat transferred through contact Convection Heat transfer through fluids (air and water Heat is less dense and rises, cold is more dense and sinks

Heat Transfer 50% is absorbed by earth 20% is absorbed by clouds and atmosphere 30% is reflected back to space

Atmosphere Structure 4 layers determined by temperature gradients

Troposphere Closest layer to the Earth Where all weather occurs Air close to ground is heated by conduction causing temperature to decrease with altitude

Stratosphere Ozone causes temperature to increase with altitude

Temperatures decrease with altitude as you move away from ozone Meteors burn up from friction with our atmosphere Mesosphere

Thermosphere Outermost layer Temperatures increase with altitude due to UV radiation from the sun Auroras found here

Ozone Ozone is a molecule consisting of 3 oxygen atoms Ozone in the stratosphere is necessary for life on Earth Ozone in the troposphere is a pollutant (smog!) Ozone

Stratospheric Ozone Ozone can be created or destroyed by the Sun’s UV rays

Stratospheric Ozone CFCs (chlorofluorocarbons) and other ozone depleting compounds breakdown and prevent new ozone from forming

Thinning of the ozone layer has caused a “hole” to form Stratospheric Ozone

Stratospheric Ozone Good News! The Montreal Protocol (1987) An international agreement to reduce ozone depleting compounds like CFCs The ozone layer should recover by 2050