Atmosphere:The thin envelope of gases surrounding the earth Highly compressible Density decreases rapidly with height Air:A mechanical mixture of gases and aerosols Definitions
Vertical Structure of Atmosphere • Troposphere (surface to 8-20 km) Upper boundary varies from about 8 km (poles in winter) to about 20 km (tropics) Weather and climate layer Most of atmosphere’s mass; all of its water
Vertical Structure of Atmosphere • Troposphere (surface to about 8-20 km) Upper boundary varies from about 8 km (poles in winter) to about 20 km (tropics) Weather and climate layer Most of atmosphere’s mass; all of its water • Stratosphere (8-20 km up to about 50 km) Ozone (O3) Layer Temperature inversion
Vertical Structure (ctd.) • Mesosphere (50-80 km) • Temperature decreases with height. Why? • Thermosphere (80-? km) • Temperature inversion. Why?
Vertical Structure (ctd.) • Homospherevs. Heterosphere
Vertical Structure (ctd.) • Homospherevs. Heterosphere • Transition zones between layers • Tropopause • Stratopause • Mesopause
Defining Layers by Function – the Ozonosphere • Roughly corresponds to the stratosphere • How does the ozone layer work? • Why is there a “hole” in the ozone layer? • Why no “hole” where the pollution is produced?
Defining Layers by Function – the Ionosphere • Upper mesosphere + thermosphere • Produces the aurora borealis and aurora australis • D Layer – absorbs AM radio waves; disappears at night • E Layer – weakens at night • F Layer – reflects AM radio waves
Composition of the Air • Uniform gases Nitrogen (N2) 78%, (O2) 21%, Argon (Ar) 1%, trace gases (Neon, Helium, Methane (CH4), etc.) • Variable gases Water Vapor (H2Ov), O3, CO2
Composition (ctd.) • Aerosols Solid: Ice/salt crystals, soil particles, volcanic dust Condensation nuclei Liquid: Water droplets (cloud, fog)
Origin of the Atmosphere • Volcanoes release H2, CO2, H2Ov, N2, NH3, CH4 No O2 or O3, so no land organisms! • One-celled aquatic organisms release CO2 to atmosphere when breaking down food through fermentation • Simple aquatic plants took in CO2 and released O2 to atmosphere via photosynthesis O3 formed from the O2
Origin of Atmosphere (ctd) • CO2 gets stored in shells and decaying plants • N2 builds up in atmosphere