The Structure of the Atmosphere What are the main gases in our atmosphere? Nitrogen (78%) Oxygen (21%) Argon and all others (ozone, Carbon dioxide water vapor etc.) (~1%) We divide our atmosphere into 4 layers based on temperature Troposphere Stratosphere Mesosphere Thermosphere

Troposphere Troposphere: Temp. and pressure drop as you go up layer closest to the Earth's surface extending up to about 10-15 km above the Earth's surface. contains 75% of the atmosphere's mass Most clouds/weather occur in the troposphere. Temp. and pressure drop as you go up

Stratosphere Above the troposphere extends from about 15 to 50 km above the Earth's surface Temp. increases with altitude because of absorption of sunlight by ozone (ozone layer) Temperature increases with altitude Stratopause

Mesosphere Above the stratosphere Extending from 50 to 80 km above the Earth's surface A cold layer where the temp. decreases with increasing altitude Where meteors burn up

Thermosphere Extends from 80 km – 320 km Temp. is hot However, the thermosphere would actually feel very cold to us because so few molecules will hit our skin and transfer enough energy to cause appreciable heat

What does our atmosphere do? Two main natural processes Greenhouse effect – keeping the planet warm through absorbing long wave radiation from the planet (water, CO2, CH4) Ozone shield – blocking unwanted UV radiation Protects life on earth from cataracts, skin cancer.