The Atmosphere

Atmospheric Composition Grab a handful of air… Earth’s atmosphere is mostly nitrogen and oxygen N2 (78%) and O2 (21%) make up 99% of the atmosphere Less than 1% is other gases, such as argon, carbon dioxide (CO2), methane, water vapor, dust

Earth’s Atmosphere

Key Atmospheric Gases (Small but mighty) Water Amount changes constantly, 0-4% Source of clouds and precipitation Absorbs heat given off by Earth and some solar energy Ozone (O3) Very small amount (>0.01%) Absorbs harmful UV radiation Protects our skin from sun damage Carbon dioxide (CO2) 0.03% Absorbs heat, contributes to global warming

Human Influences on Atmosphere (Air pollutants) Depletion of ozone layer by use of chloroflorocarbons (CFCs) – aerosols, refrigerants, some Styrofoam Automobiles account for 33% of CO2 emissions, contributing to global warming Air pollution…includes carbon monoxide, nitrogen oxides, sulfur oxides, metals, ammonia, particles (e.g., dust), methane How does this affect us? Asthma, lung cancer, respiratory illness, heart disease

Primary Pollutants

Atmospheric structure The atmosphere is made up of 4 main layers, determined by temperature and composition: Troposphere Stratosphere Mesosphere Thermosphere

Troposphere Sphere of weather Thinnest layer of the atmosphere Temperatures decrease with height (Have you ever been to the top of a mountain?) Height: 0 to 12 km

Snowy Mountaintops Contrast with Warmer Snow-Free Lowlands

Stratosphere Temperatures increase Ozone layer Height: 12km to 50km

Mesosphere Temperatures decrease Temperatures as low as -90◦ C Height: 50km to 80km Meteors are broken up

Thermosphere Temperatures increase Oxygen and nitrogen absorb solar radiation Northern lights 80km to…? (no defined upper limit)

Temperature v. Heat Temperature: measurement of the kinetic energy (energy of motion) of atoms or molecules Faster motion = higher temp. Heat: transfer of energy from one object to another because of a difference in temperature Heat flows from higher to lower temp. Radiation, conduction, convection Heat fuels the weather, and temperature measures it!

Pressure-Density-Temperature Relationship Air pressure: weight of the air pressing down gases at the top press down on the ones below Density: measure of particles in a given space More particles = higher density Temperature: proportional to pressure, inversely proportional to density Atmospheric Relationships As T ↑ , P ↑ As T ↓, D ↑ As T ↑ , D ↓ T = Temperature P = Pressure D = Density ↑ = Increases ↓ = Decreases

Air Pressure v. Altitude Altitude: measure of distance “up” in the air Pressure ↓ as altitude ↑ Why is it harder to breathe at the top of a mountain? Components of the atmosphere