The Atmosphere

1. The Atmosphere Chapter 22

2. Characteristics of the Atmosphere • 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 CO2 and H2O.

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

4. Nitrogen Cycle • Nitrogen-fixing bacteria in soil change N2 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 N2 to the atmosphere.

5. oxygen photosynthesis respiration carbon dioxide • Oxygen cycle

6. Oxygen Cycle • Animals, fungi, and bacteria remove Oxygen from the air for cellular respiration. They release CO2 as waste. • Plants remove CO2 from the air for photosynthesis and release O2 as waste.

7. precipitation condensation transpiration evaporation surface runoff lake water storage in ocean groundwater seepage Water cycle

8. 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.

9. Ozone (O3) 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.

10. 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.

11. Atmospheric Pressure • 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)

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

13. 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

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

15. 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.

16. Solar Energy and the Atmosphere • Radiation – all forms of energy that travel through space as waves known as the Electromagnetic Spectrum

18. 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.

20. 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

21. Snow and ice reflect 50 to 90%

22. Forests reflect 5 to 10%

23. 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

24. 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.

25. 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

27. 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.

28. Transfer of 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

29. Atmospheric Circulation • 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 - the 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

30. Coriolis Effect

31. 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

32. 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

33. 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