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The Atmosphere Characteristics of the Atmosphere Composition: • 78% nitrogen gas. • 21% Oxygen • 1% “Other” • 0.9% Argon (noble gas) • 0.04% CO2 • 0.06% is trace elements (tiny bits): • Water vapor • Ozone (O3) • Methane (CH4) • Other noble gases (He, Ne, Kr) Characteristics of the Atmosphere Pressure and Temperature: • The atmosphere is held around the Earth by gravity. Gravity pulls gas molecules in the atmosphere toward the Earth s surface, causing air pressure. • As altitude increases, air pressure decreases. • Air temperature decreases as altitude increases. Lower parts of the atmosphere are warmer because they contain a high percentage of gases that absorb solar energy. Air Pressure • Atmospheric Pressure – amount of force or pressure exerted by atmosphere on objects within it • Stronger push = high pressure • Weaker push = low pressure • Differences in pressure cause air to move to even out pressures. This is wind! • Pressure and Density: • Low air density = low pressure • High air density = high pressure • Pressure and Temperature (of contained particles) • Low temperature = slow particles = low pressure • High temperature = fast particles = high pressure What Makes Wind? Movie Measuring Pressure • Barometer: A tool that measures the pressure in the atmosphere. It is used by meteorologists to predict weather patterns. • Types of Barometers: • Water – colored water in sealed bubble with tube • Water in tube above line: low pressure • Water in tube below line: high pressure • Mercury – liquid mercury (Hg) rises/falls in a tube as pressure rises/falls (where we get the term millimeters of mercury or mmHg) • Aneroid – metal cell changes shape due to changes in air pressure, which translate to the dial Layers of the Atmosphere • The Troposphere: The Layer in Which We Live The lowest layer of the atmosphere, it extends 4-12 miles above Earth, depending on your location. Temperature drops as you climb higher because the gases decrease (“thinner air”). Almost all weather happens here. • The Stratosphere: Home of the Ozone Layer Above the troposphere, it extends about 31 miles above Earth. It contains a lot of oxygen, which absorbs radiation and forms the Ozone. This results in increasing temperature as height increases. (closer to more ultraviolet radiation from the Sun) Layers of the Atmosphere • The Mesosphere: The Middle Layer The middle layer of the atmosphere extends about 53 miles above Earth. The gases become thinner and are less effected by UV rays, so temperature decreases with height. It is the coldest layer (5F -184F). The gases are thick enough to slow meteorites, where they burn up leaving meteor showers. Layers of the Atmosphere • The Thermosphere: The Edge of the Atmosphere The uppermost atmospheric layer extends 430 miles above Earth. The gases are increasingly thinner, and can only absorb higher energy UV and X-rays from the sun. Temperature increases with height (closer to the sun’s rays). • The Exosphere: The Outermost Layer: 6200 miles above Earth and composted mostly of Hydrogen and Helium, these particles are so spread out that they rarely interact. They eventually leave by the solar wind. This is where satellites orbit. Layers of the Atmosphere • The Ionosphere: Home of the Auroras Part of the layers of the upper atmosphere, nitrogen and oxygen atoms become ionized (charged) from solar energy. This can result in auroras Layers of the Atmosphere Draw me! Energy In the Atmosphere • Radiation: The Earth receives energy from the sun by radiation. Radiation is the transfer of energy as electromagnetic waves. • Conduction: Thermal conduction is the transfer of thermal energy through contact with a material. • Convection: Convection is the transfer of thermal energy by the circulation or movement of a liquid or gas. Atmospheric Heating The Greenhouse Effect • The Greenhouse Effect: The greenhouse effect is the process by which gases in the atmosphere absorb thermal energy and radiate it back to Earth. Global Warming • Greenhouse Gases and Global Warming Some scientists think that an increase of greenhouse gases in the atmosphere may be the cause of global warming. Why Air Moves • Uneven Heating by the Sun: Air rises at the Equator and sinks at the poles. As the cold air sinks, it creates areas of high pressure around the poles. This cold polar air then flows toward the equator. Why Air Moves • Pressure Belts Are Found Every 30º Convection cells are separated by pressure belts, bands of high and low pressure. The Coriolis Effect • The Coriolis Effect The apparent curving of the path of currents due to the Earth s rotation. 1835 – Gaspard Gustave Coriolis observed and calculated veering effect mathematically Global Winds Types of Global Winds • Polar Easterlies are the wind belts that extend from the poles to 60° latitude in both hemispheres. • Westerlies are the wind belts found between 30° and 60° latitude in both hemispheres. • Trade Winds are the winds that blow from 30° latitude almost to the equator in both hemispheres. Global Winds • The Doldrums The trade winds of the Northern and Southern Hemispheres meet in an area around the equator. • The Horse Latitudes At about 30° north and 30° south latitude, sinking air creates an area of high pressure. • Jet Streams are narrow belts of highspeed winds that blow in the upper troposphere and lower stratosphere. Global Winds – Draw Me! Local Winds • Generally move short distances and can blow from any direction. • Mountain and valley breezes are examples of local winds caused by an area s geography. • Sea and land breezes are affected by temperature. Sea Breeze & Land Breeze Sea Breeze Land Breeze