Earth’s Atmosphere September 20, 2010

Composition Nitrogen: 78% Oxygen: 21% Trace Elements: 1%

Composition Mixture of gases, liquids, and solids Water is the only substance present in all three states –Gas: Water Vapor –Liquid: Water –Solid: Ice

Atmospheric Layers TROPOSPHERE: –Closest to the surface of Earth: where we live! –Contains 75% of atmospheric gases –Weather, clouds, and smog occur here STRATOSPHERE: –Contains ozone layer

Atmospheric Layers MESOSPHERE THERMOSPHERE –Includes ionosphere, layer of electrically charged particles, reflects radio waves –International Space Station orbits in this layer EXOSPHERE –Uppermost part of the atmosphere; last layer before space –No clear boundary between atmosphere and space

Atmospheric Pressure Gravity pulls gases towards Earth Pressure increases closer to the ground Upper layers compress the lower layers of the atmosphere

Temperature Heated molecules move faster and spread out, causing areas of low pressure Cooled molecules move slower and are more dense, causing areas of high pressure Areas of low and high pressure affect weather patterns

Energy from the Sun Sun=source of all energy in our atmosphere Three different things happen to that energy: –1. Reflected back into space –2. Absorbed into the atmosphere –3. Absorbed by land and water surfaces

Energy from the Sun Radiation: transfer of energy by waves –Ex: sun warms your car on a hot day, heat from a campfire Conduction: transfer of energy when molecules bump into one another –Ex: stove burner transferring energy to pot, walking on hot asphalt

Energy from the Sun Convection: transfer of heat by the flow of heated material (air, liquid) –Cool material sinks because of higher density, hot material rises because of lower density –Causes a constant current…in the atmosphere it’s called a convection current –Ex: furnace heating a house