Chapter 22

 Atmosphere – layer of gases that surrounds Earth.  Composition ◦ Most abundant elements in air are Nitrogen, Oxygen, and Argon  Nitrogen makes up 78% of Earth’s atmosphere  Oxygen makes up 21% of Earth’s atmosphere ◦ Two most abundant compounds in air are CO 2 and H 2 O.

nitrogen in atmosphere animals denitrifying bacteria nitrifying bacteria nitrifying bacteria ammonium ammonification decomposers plant nitrogen-fixing bacteria in soil nitrogen-fixing bacteria in roots nitrates nitrites  Nitrogen Cycle

◦ Nitrogen-fixing bacteria in soil change N 2 into nitrogen compounds. ◦ Nitrogen compounds in plants are consumed by animals ◦ Nitrogen compounds return to the soil in wastes ◦ Decay and processes in the soil return N 2 to the atmosphere.

 Oxygen cycle oxygen respiration carbon dioxide photosynthesis

 Oxygen Cycle ◦ Animals, fungi, and bacteria remove Oxygen from the air for cellular respiration. They release CO 2 as waste. ◦ Plants remove CO 2 from the air for photosynthesis and release O 2 as waste.

precipitation condensation transpiration evaporation water storage in ocean surface runoff lake groundwater seepage

 Water Cycle ◦ Water evaporates as gas water vapor from oceans, lakes, streams, and soil. ◦ Plants and animals release water vapor into the air during transpiration. ◦ Water vapor is removed from air by condensation and precipitation. ◦ The amount of water vapor in the air depends on time of day, location, and season.

 Ozone (O 3 ) in the Atmosphere ◦ Ozone layer found in upper layer of the atmosphere and absorbs harmful ultraviolent radiation from the sun. ◦ Damage to Ozone layer caused by release of Chlorofluorocarbons (CFCs), previously used in refrigerators and air conditioners, and nitrogen oxide from exhaust.

 Particulates in the Atmosphere ◦ Tiny solid particles which may include volcanic dust, ash from fires, microscopic organisms, mineral particles lifted from soil by winds, pollen from plants, etc.

 Gases are held near the Earth’s surface by gravity ◦ 99% of the total mass of the atmosphere is held within 32km of Earth’s surface  Air molecules are compressed together and exert a force on any surface.  Pressure decreases as altitude increases ◦ The pull of gravity is not as strong at higher altitudes, so the molecules are farther apart and exert less pressure ◦ Measured with a barometer  Average atmospheric pressure at sea level is 1 atmospheres (atm)

Distinctive pattern of temperature changes with increasing altitude caused by differences in absorption of solar energy.

 Troposphere ◦ Closest to Earth’s surface ◦ Extends to nearly 12km ◦ Contains all water and carbon dioxide ◦ All weather occurs here ◦ Air is heated by thermal energy radiated from Earth’s surface ◦ Temperature decreases with altitude

 Stratosphere ◦ Extends to nearly 50km ◦ Contains almost all of the ozone ◦ Temperature increases with altitude as ozone absorbs solar radiation

 Mesosphere ◦ Extends to about 80km ◦ Temperature decreases with altitude to nearly -90°C  Thermosphere ◦ Temperature increases with altitude because nitrogen and oxygen absorb solar radiation ◦ Temperatures recorded at more than 1,000°C ◦ Contains the Ionosphere  Atoms of gas molecules lose electrons producing ions and free electrons.  Reactions between solar radiation and ionosphere produce auroras.

 Radiation – all forms of energy that travel through space as waves known as the Electromagnetic Spectrum

 As solar radiation passes through the atmosphere ◦ Shorter wavelengths (X-rays, gamma rays, and ultraviolet rays) are absorbed in the upper atmosphere ◦ Longer wavelengths (infrared and visible light) that reach the lower atmosphere are absorbed by carbon dioxide, water vapor, and other molecules in the troposphere. ◦ Scattering occurs when particles and gas molecules reflect and bend solar rays changing their direction, but not wavelength  Causes the sky to be blue and the sun to be red at sunrise and sunset.

 When solar radiation reaches Earth’s surface, it is either absorbed or reflected depending on the color, texture, composition, volume, mass, transparency, state of matter, and specific heat of the material.  Albedo is the solar radiation that is reflected by earth’s surface. ◦ 30% of the solar energy that reaches Earth’s atmosphere is reflected or scattered ◦ Earth’s albedo is 0.3

 Snow and ice reflect 50 to 90%

 Forests reflect 5 to 10%

 Surfaces heated by incoming solar radiation convert the energy into infrared rays of longer-wavelengths and reemit it.  Those wavelengths of infrared rays are absorbed by carbon dioxide, water vapor, and other gas molecules in the atmosphere.  This absorption and release of energy keeps the earth’s surface warmer than it would be without an atmosphere and is known as the Greenhouse Effect

 Greenhouse Effect Human Human Impact on the Greenhouse Effect  Amount of Carbon Dioxide in the atmosphere has been increasing due to burning fossil fuels  Increases in Carbon Dioxide is believed to be directly proportional to increase in energy absorption by the atmosphere and increase in global temperature.

 Temperature Variations  Temperature of the atmosphere depends on ◦ Latitude  Affects the angle the sun’s rays strike an area  Energy that reaches the equator is at 90° angle and is more intense than at lower latitudes ◦ Surface features  Determines the amount of energy absorbed, reflected and reradiated. ◦ Time of year and day  Tilt of the Earth’s axis determines seasons as the hemisphere tilted toward the sun receives direct, more intense energy from the sun

 Water Vapor in the Air and Surface absorbs and holds energy ◦ Water has high specific heat. It requires a lot of energy to increase its temperature, but will take a long time to cool down. ◦ Areas having less water vapor, such as deserts, tend to warm during the day but cool very quickly at night. ◦ Areas with high quantities of water vapor, such as near large bodies of water, generally have more moderate temperatures as the water vapor absorbs and holds the sun’s energy.

 Conduction ◦ Transfer by direct contact ◦ Lowest few centimeters of the atmosphere are heated by conduction  Convection ◦ Transfer within a liquid or a gas ◦ Less dense gas or liquid rises, more dense sinks creating convection currents.  Creates ocean currents and wind

 Pressure differences in the atmosphere cause the movement of air  Air near the surface generally flows from the high-pressure, cold, poles toward the lower- pressure, warm, equator.  Coriolis Effect - t he tendency of a moving object to follow a curved path rather than a straight path because of the Earth’s rotation. ◦ Northern Hemisphere – currents curve to the right, or clockwise ◦ Southern Hemisphere – currents curve to the left, or counterclockwise

 Coriolis Effect

 Global Winds ◦ Convection cells - 3 looping patterns of air flow in each hemisphere create wind belts, also known as prevailing winds Trade Winds – flow toward the equator Westerlies – flow in the mid-latitudes Polar Easterlies

 Wind and Pressure Shifts ◦ As the sun’s rays shift during changing seasons, the position of pressure belts and wind belts shift. ◦ Example: The westerlies prevail in Southern Florida during the winter, but trade winds dominate in the summer.  Jet Streams ◦ Narrow bands of high-speed winds that blow in the upper troposphere and lower stratosphere ◦ Sometimes 100km wide and 2 to 3 km thick reaching speeds of 500km/h ◦ Affect airline routes and storm paths

 Local Winds ◦ Influenced by local temperature variations ◦ Gentle winds that extend over less than 100km.  Land Sea Breezes  Land surfaces heat up faster than water surfaces. Air over land warms, rises, and cool air over water moves in to replace it.  Reverses at night as land surfaces cool faster than water.  Mountain and Valley Breezes  Warm air from the valley moves upward during the day  At night, cool air descends from the mountain peaks and settles in the valley