The Atmosphere

Composition  Nitrogen  Oxygen  Other –Argon –Carbon Dioxide –Methane –Water Vapor  Atmospheric dust

Nitrogen  Most abundant  78%  Volcanoes erupt  Dead plants and animals decay

Oxygen  2 nd most abundant  about 21%  Produced by plants

Atmospheric Dust  Mostly soil  Salt  Ash from fires  Volcanic fires  Explosion matter  People bits- skin, hair, bits of clothing  Pollen  Bacteria & Viruses  Aerosols- tiny liquid droplets

Air Pressure  Atmosphere pulled by gravity  THUS denser near Earth’s surface  Most Earth’s atmospheric gases located within 30 km of surface  Why is it harder to breathe at higher elevations?

Layers  Troposphere –18 km above Earth’s surface  Stratosphere –18-50 km  Mesosphere –50-80 km  Thermosphere – km

Troposphere  Nearest Earth  Almost all weather occurs here  Densest layer –Why?  Temperature decreases as altitude increase

Stratosphere  Temperature rises as altitude rises  Contains ozone layer –absorbs UV radiation  reduces amount of UV radiation hitting the surface –How does this help us?  Ozone absorbs UV energy & warms air  Ozone- molecule made of three oxygen atoms

Mesosphere  Coldest layer  Temperatures have reached -93° C

Thermosphere  Nitrogen & Oxygen absorb UV radiation  2,000°C  Would not feel hot –VERY THIN –particles rarely collide to transfer heat

Lower Thermosphere  N & O atoms in lower thermosphere absorb harmful solar radiation (X & gamma rays)  Ions- electrically charger particles  seen in North and South Poles  Ionosphere

Layers

Energy in the Atmosphere  Radiation- transfer of energy across space  Conduction -flow of energy from direct conduct of a warmer object to a cooler object  Convection- transfer of heat from air currents

Energy  Solar energy reaches Earth as electromagnetic radiation –Visible Light –Infrared Radiation –Ultraviolet Light  Only two BILLIONTHS of sun’s energy reach Earth

Energy Absorption  Only HALF of the solar energy that enters atmosphere reaches Earth’s surface  Other half: –Absorbed or reflected by clouds, gases, or dust –Reflected by Earth’s surface  Why does the Earth just get hotter and hotter?

Heating  Oceans and land radiate the energy they have absorbed BACK into the atmosphere  Dark colored objects absorb more than light colored objects  Cities tend to be hotter in temperature than countryside

Movement of Energy in Atmosphere  Hotter air=less dense  Cooler air=more dense  Air is heated  rises  Air cools  falls  Convection Currents: rising and falling of air with the heating and cooling

Greenhouse Effect  Sunlight enters atmosphere, heat is radiated back, some escapes, REST is absorbed by greenhouse gases and radiated back to surface

Greenhouse Gases  Trap and radiate heat  Not a high concentration of them in atmosphere  Abundant gases: –Water vapor –Carbon dioxide –Methane –Nitrous oxide  Carbon dioxide and methane results from industrial processes