Section 11.1 – Atmosphere Basics 8th Grade Earth and Space Science Class Notes
Atmosphere Basics • Combination of gases, dust, water droplets, and ice crystals • Surrounds the Earth • Extends from the Earth’s surface to outer space Picture of the Earth’s atmosphere taken from a space shuttle
Permanent Atmospheric Gases • Earth’s atmosphere consists mainly of nitrogen (78 percent) and oxygen (21 percent). • The amounts of nitrogen and oxygen in the atmosphere are fairly constant over recent time.
Variable Atmospheric Gases • The concentrations of some atmospheric gases are not as constant over time. • The amount of water vapor, ozone, and carbon dioxide vary significantly from place to place.
Water Vapor (H2O(g)) • Invisible, gaseous form of water • Can range of 0% - 4% • Concentration depends on the seasons, altitude, and properties of the surface underneath
Carbon Dioxide (CO2) • During the past 150 years, the concentration of atmospheric carbon dioxide has increased, due primarily to the burning of fossil fuels. • Currently 0.039% (up by 0.028%)
Ozone (O3) • Mostly in ozone layer (20 – 50 km above) • Only 0.0012% but plays important role in blocking out harmful rays from the sun • Concentration has decreased due to CFCs which are now banned • Scientists estimate it should fully recover by the 2100
Atmosphere Particles • Contains variable amounts of solids in the form of tiny particles, such as dust, salt, and ice • Fungi and bacteria are often attached to these particles Fluorescent sample of bacteria taken from the air.
Troposphere • Closest to the Earth’s surface • Contains most of the atmosphere’s mass • Weather occurs in this layer • Air temperature decreases with altitude • Top is called tropopause
Stratosphere • Above tropopause • Contains the ozone layer • Air temperature increases with altitude since the ozone layer absorbs the sun’s energy • Ends at the stratopause
Mesosphere • Above the stratopause • Air temperature decreases with altitude since very little solar radiation is absorbed • Ends at mesopause
Thermosphere • Low air density so temperature rises (can be over 1000°C) • Contains the ionosphere (made up of charged particles) • Ends at thermopause
Exosphere • Outermost layer • Transitional region between the Earth’s atmosphere and outer space
Review of Thermal Energy and Heat • Remember – all matter is made of particles in constant, random motion! • These moving particles contain kinetic energy. • The total kinetic energy of the moving particles is called thermal energy. Less thermal energy More thermal energy
Review of Thermal Energy and Heat • Heat is the transfer of thermal energy from regions of higher temperature to regions of lower temperature Direction of movement
Energy Transfer in the Atmosphere • In the atmosphere thermal energy is transferred by: • Radiation • Conduction • Convection
Radiation • Transfer of thermal energy by electromagnetic waves • Thermal energy is transferred from the Sun to Earth by radiation
Absorption and Reflection • Incoming solar radiation is either reflected back into space or absorbed by Earth’s atmosphere or its surface. • 30% reflected • 20% absorbed by atmosphere and clouds • 50% absorbed by Earth’s surface
Rate of Absorption • Depends on physical characteristics of the surface and the amount of solar radiation • Examples – water heats and cools more slowly; dark colors absorb energy faster Solar Radiation Around the World Darker = more
Conduction • Transfer of thermal energy when objects at two different temperatures are in contact • Occurs between the Earth’s surface and lowest part of the atmosphere
Convection • Remember – convection is the transfer of thermal energy by the movement of heated material from one place to another • Near the Earth’s surface air becomes heated, expands, and rises then as it rises it cools, contracts, and sinks. • This creates convection currents in the atmosphere.