GEOG101 Chapter 4 Lecture


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GEOG101 Chapter 4 Lecture

  1. 1. Overview <ul><li>Air Temperature </li></ul><ul><li>Air Pressure and Winds </li></ul><ul><li>Ocean Currents </li></ul><ul><li>Moisture in the Atmosphere </li></ul><ul><li>Climate Regions </li></ul><ul><li>Climatic Change </li></ul>
  2. 2. Weather vs. Climate <ul><li>Weather </li></ul><ul><ul><li>State of the atmosphere at a given time and place </li></ul></ul><ul><li>Climate </li></ul><ul><ul><li>Long-term average weather conditions in a place </li></ul></ul><ul><li>Troposphere is of particular concern </li></ul><ul><ul><li>Atmospheric layer closest to the earth </li></ul></ul><ul><ul><li>Contains virtually all of the air, clouds, and precipitation of the earth </li></ul></ul>
  3. 3. Air Temperature <ul><li>Insolation </li></ul><ul><ul><li>Solar radiation received at the earth’s surface </li></ul></ul><ul><ul><ul><li>Determined by angle of the sun’s rays and number of daylight hours </li></ul></ul></ul><ul><li>Modifying variables </li></ul><ul><ul><li>Amount of water vapor in the air </li></ul></ul><ul><ul><li>Cloud cover </li></ul></ul><ul><ul><li>Nature of the surface of the earth </li></ul></ul><ul><ul><li>Elevation </li></ul></ul><ul><ul><li>Degree and direction of air movement </li></ul></ul>
  4. 4. Earth Inclination <ul><li>Axis of the earth tilts at ≈ 23.5° </li></ul><ul><li>Summer Solstice (about June 21) </li></ul><ul><ul><li>Northern hemisphere tilted toward the sun </li></ul></ul><ul><ul><li>Vertical rays of the sun at 23.5° N </li></ul></ul><ul><li>Winter Solstice (about December 21) </li></ul><ul><ul><li>Northern hemisphere tilted away from the sun </li></ul></ul><ul><ul><li>Vertical rays of the sun at 23.5° S </li></ul></ul><ul><li>Spring and fall equinoxes (about March 21 and September 21) </li></ul><ul><ul><li>Vertical rays of the sun at equator </li></ul></ul>
  5. 5. Earth Inclination <ul><li>Variation in length of days and nights </li></ul><ul><ul><li>At the equator </li></ul></ul><ul><ul><ul><li>12 hours of light each day of the year </li></ul></ul></ul><ul><ul><li>Inside the Arctic Circle and Antarctic Circle </li></ul></ul><ul><ul><ul><li>24 hours of daylight/darkness on solstice </li></ul></ul></ul><ul><li>Angle of the sun’s rays </li></ul><ul><ul><li>More direct angle = more energy available </li></ul></ul>
  6. 6. Reflection and Reradiation <ul><li>Clouds and light colored surfaces reflect solar energy </li></ul><ul><li>Reradiation </li></ul><ul><ul><li>Shortwave solar energy absorbed, returned into the atmosphere as longwave terrestrial radiation </li></ul></ul><ul><li>Water heats and cools more slowly </li></ul><ul><ul><li>Marine environment </li></ul></ul><ul><ul><ul><li>Cooler summers, warmer winters </li></ul></ul></ul><ul><li>Land heats and cools more rapidly </li></ul><ul><ul><li>Continental environment </li></ul></ul><ul><ul><ul><li>Hotter summers, colder winters </li></ul></ul></ul>
  7. 7. The Lapse Rate <ul><li>Temperature generally decreases as altitude increases </li></ul><ul><ul><li>Lapse rate </li></ul></ul><ul><ul><ul><li>Average of 3.5° F per 1000 feet (6.4 ° C per 1000 m) </li></ul></ul></ul><ul><li>Temperature inversion </li></ul><ul><ul><li>Cooler air trapped below warmer air </li></ul></ul><ul><ul><ul><li>Contributes to smog problems </li></ul></ul></ul>
  8. 8. Air Pressure and Winds <ul><li>Weight of the atmosphere </li></ul><ul><li>Air pressure is higher closer to the earth’s surface </li></ul><ul><li>Temperature and air pressure </li></ul><ul><ul><li>Cold air is denser: high pressure </li></ul></ul><ul><ul><li>Warm air is lighter: low pressure </li></ul></ul><ul><li>Air pressure is measured by a barometer </li></ul>
  9. 9. Air Pressure and Winds <ul><li>Zones of high and low air pressure </li></ul><ul><li>Pressure gradient force </li></ul><ul><ul><li>Causes air to flow from high to low pressure areas </li></ul></ul><ul><ul><li>Wind </li></ul></ul><ul><ul><ul><li>Velocity is in direct proportion to pressure differences </li></ul></ul></ul><ul><li>Convection </li></ul><ul><ul><li>Circulatory movement of rising warm air and descending cool air </li></ul></ul>
  10. 10. Air Pressure and Winds <ul><li>Land and sea breezes </li></ul><ul><ul><li>Day: from sea to land </li></ul></ul><ul><ul><li>Night: from land to sea </li></ul></ul><ul><li>Mountain and valley breezes </li></ul><ul><ul><li>Day: from valley to mountains </li></ul></ul><ul><ul><li>Night: from mountains to valley </li></ul></ul>
  11. 11. Air Pressure and Winds <ul><li>Coriolis effect </li></ul><ul><ul><li>Apparent deflection relative to the earth’s surface </li></ul></ul><ul><ul><ul><li>Northern Hemisphere: wind veers toward the right Southern Hemisphere: wind veers toward the left </li></ul></ul></ul><ul><ul><li>Spiral wind patterns </li></ul></ul><ul><li>Frictional effect </li></ul><ul><ul><li>Decreases wind speed </li></ul></ul><ul><ul><li>Changes wind direction </li></ul></ul>
  12. 12. Global Air-Circulation Pattern <ul><li>Equatorial low pressure </li></ul><ul><li>Subtropical high pressure </li></ul><ul><ul><li>About 30 ° N and 30° S of the equator </li></ul></ul><ul><li>Trade winds </li></ul><ul><ul><li>In the tropics </li></ul></ul><ul><li>Westerlies </li></ul><ul><ul><li>In the midlatitudes </li></ul></ul><ul><li>Subpolar low </li></ul><ul><li>Polar easterlies </li></ul><ul><li>Polar high </li></ul>
  13. 13. Global Air-Circulation Pattern <ul><li>Jet streams </li></ul><ul><ul><li>Belts of strong winds in the upper atmosphere </li></ul></ul><ul><ul><ul><li>From west to east </li></ul></ul></ul><ul><ul><li>Guide the movement of weather systems </li></ul></ul><ul><li>Monsoon </li></ul><ul><ul><li>Wind system that reverses direction seasonally </li></ul></ul><ul><ul><ul><li>Produces wet and dry seasons </li></ul></ul></ul><ul><ul><li>Significant effect on parts of southern and eastern Asia </li></ul></ul><ul><ul><ul><li>Farm economy is dependent upon summer monsoon rains </li></ul></ul></ul><ul><ul><ul><li>Flooding </li></ul></ul></ul>
  14. 14. Ocean Currents <ul><li>Movement due to winds and differences in water density </li></ul><ul><ul><li>Direction also influenced by landmasses and shape of ocean basins </li></ul></ul><ul><li>North Atlantic drift </li></ul><ul><li>Ocean currents affect temperature and precipitation on adjacent land areas </li></ul><ul><ul><li>Cold currents </li></ul></ul><ul><ul><ul><li>Dry conditions </li></ul></ul></ul><ul><ul><li>Warm currents </li></ul></ul><ul><ul><ul><li>Moist conditions </li></ul></ul></ul>
  15. 15. Moisture in the Atmosphere <ul><li>Ascending air expands and cools </li></ul><ul><ul><li>Less able to hold water vapor </li></ul></ul><ul><li>Supersaturated air </li></ul><ul><ul><li>Water vapor condenses around condensation nuclei </li></ul></ul><ul><li>Clouds </li></ul><ul><ul><li>Rain droplets or ice crystals supported by upward movements of air </li></ul></ul><ul><ul><ul><li>Droplets may coalesce and fall as precipitation </li></ul></ul></ul><ul><ul><li>Form and altitude depends on: </li></ul></ul><ul><ul><ul><li>Water vapor content, temperature, wind movement </li></ul></ul></ul>
  16. 16. Moisture in the Atmosphere <ul><li>Relative humidity </li></ul><ul><ul><li>Percentage measure of the moisture content of the air </li></ul></ul><ul><ul><ul><li>Amount present relative to the maximum that can exist at the current temperature </li></ul></ul></ul><ul><li>Dew point </li></ul><ul><ul><li>Temperature at which condensation forms </li></ul></ul>
  17. 17. Types of Precipitation <ul><li>Convectional precipitation </li></ul><ul><ul><li>Heated, moisture-laden air rises and then cools below the dew point </li></ul></ul><ul><ul><li>Summer in tropical and continental climates </li></ul></ul><ul><li>Orographic precipitation </li></ul><ul><ul><li>Warm, moisture-laden air is forced to rise over hills or mountains and is thereby cooled </li></ul></ul><ul><ul><ul><li>Windward side </li></ul></ul></ul><ul><ul><ul><ul><li>Receives a great deal of precipitation </li></ul></ul></ul></ul><ul><ul><ul><li>Leeward side </li></ul></ul></ul><ul><ul><ul><ul><li>Very often dry (rain shadow) </li></ul></ul></ul></ul>
  18. 18. Types of Precipitation <ul><li>Cyclonic (frontal) precipitation </li></ul><ul><ul><li>Cool and warm air masses meet </li></ul></ul><ul><ul><li>Common to the midlatitudes </li></ul></ul><ul><ul><li>In the tropics—originator of hurricanes and typhoons </li></ul></ul><ul><ul><li>Air mass </li></ul></ul><ul><ul><ul><li>Body of air with similar temperature, pressure, and humidity characteristics throughout </li></ul></ul></ul><ul><ul><ul><li>Form over a source region </li></ul></ul></ul><ul><ul><li>Front </li></ul></ul><ul><ul><ul><li>Zone of separation between two air masses </li></ul></ul></ul>
  19. 19. Storms <ul><li>Cyclone </li></ul><ul><ul><li>Masses of air circulate rapidly about a region of low atmospheric pressure </li></ul></ul><ul><ul><li>Can develop into a storm </li></ul></ul><ul><li>Hurricane </li></ul><ul><ul><li>Severe tropical cyclone with winds exceeding 75 mph </li></ul></ul><ul><ul><li>In the Atlantic, Caribbean, or Gulf of Mexico </li></ul></ul><ul><li>Typhoon </li></ul><ul><ul><li>Hurricane in the western Pacific </li></ul></ul>
  20. 20. Storms <ul><li>Blizzard </li></ul><ul><ul><li>Heavy snow and high winds </li></ul></ul><ul><li>Tornado </li></ul><ul><ul><li>Funnel-shaped cloud of whirling winds that can form beneath a cumulonimbus cloud and moves at speeds as high as 300 mph </li></ul></ul><ul><ul><li>Esp. Central U.S. </li></ul></ul>
  21. 21. Climate Regions <ul><li>Generalizations based on daily and seasonal weather conditions </li></ul><ul><li>K öppen system </li></ul><ul><ul><li>Based on temperature, precipitation, and natural vegetation criteria </li></ul></ul><ul><ul><li>A: tropical </li></ul></ul><ul><ul><li>B: dry </li></ul></ul><ul><ul><li>C: mild midlatitude </li></ul></ul><ul><ul><li>D: midlatitude with cold winters </li></ul></ul><ul><ul><li>E: polar </li></ul></ul><ul><ul><li>H: highland </li></ul></ul>
  22. 22. Tropical Climates <ul><li>Tropical rainforest </li></ul><ul><ul><li>Equatorial low pressure </li></ul></ul><ul><ul><li>High temperatures and heavy convectional rainfall all year </li></ul></ul><ul><ul><li>Dense forests </li></ul></ul><ul><ul><li>Lack of soil nutrients </li></ul></ul>
  23. 23. Tropical Climates <ul><li>Tropical savanna </li></ul><ul><ul><li>To the north and south of rain forests </li></ul></ul><ul><ul><li>High temperatures </li></ul></ul><ul><ul><li>Heavy convectional rainfall in summer, dry winters </li></ul></ul><ul><ul><li>Forests to grasslands </li></ul></ul><ul><li>Tropical monsoon </li></ul><ul><ul><li>Significant increase in rainfall when summer monsoon winds bring water-laden air </li></ul></ul><ul><ul><li>Dense forests </li></ul></ul>
  24. 24. Dryland Climates <ul><li>Hot deserts </li></ul><ul><ul><li>Subtropical high pressure </li></ul></ul><ul><ul><li>Considerable sunshine, high temperatures </li></ul></ul><ul><ul><li>Very little precipitation </li></ul></ul><ul><ul><li>Shrubs in gravelly or sandy environments </li></ul></ul><ul><li>Midlatitude deserts and semideserts </li></ul><ul><ul><li>Warm/hot summers and cold winters </li></ul></ul><ul><ul><li>Some convectional or frontal rainfall in summer, some snowfall in winter </li></ul></ul><ul><ul><li>Grasslands, desert shrubs </li></ul></ul><ul><ul><li>Steppes have fertile soils </li></ul></ul>
  25. 25. Humid Midlatitude Climates <ul><li>Mediterranean </li></ul><ul><ul><li>Transition zone between subtropical high and westerlies </li></ul></ul><ul><ul><li>Warm/hot summers and mild/cool winters </li></ul></ul><ul><ul><li>Dry summer, frontal precipitation in winter </li></ul></ul><ul><ul><li>Shrubs and small deciduous trees </li></ul></ul><ul><li>Humid subtropical </li></ul><ul><ul><li>Hot, moist summers and moderate, moist winters </li></ul></ul><ul><ul><li>Convectional rainfall in summer, frontal precipitation in winter </li></ul></ul><ul><ul><li>Deciduous and coniferous forests </li></ul></ul>
  26. 26. Humid Midlatitude Climates <ul><li>Marine west coast </li></ul><ul><ul><li>Prevailing winds from the sea </li></ul></ul><ul><ul><li>Moderate temperatures in both summer and winter </li></ul></ul><ul><ul><li>Frontal and orographic precipitation </li></ul></ul><ul><ul><li>Deciduous and coniferous forests </li></ul></ul><ul><li>Humid continental </li></ul><ul><ul><li>Prevailing winds from the land </li></ul></ul><ul><ul><li>Hot/mild summers and cool/cold winters </li></ul></ul><ul><ul><li>Frontal and occasionally convectional rainfall in summer, snow in winter </li></ul></ul><ul><ul><li>Deciduous and coniferous forests </li></ul></ul>
  27. 27. Arctic and Subarctic Climates <ul><li>Subarctic </li></ul><ul><ul><li>Cool/cold, short summers and very cold winters </li></ul></ul><ul><ul><li>Coniferous forest to mosses and lichens </li></ul></ul><ul><ul><li>Tundra </li></ul></ul><ul><ul><ul><li>Treeless area between the Arctic tree line and the permanently ice-covered zone </li></ul></ul></ul><ul><li>Arctic </li></ul><ul><ul><li>Ice cap near the poles </li></ul></ul><ul><ul><li>Extremely cold with light precipitation </li></ul></ul>
  28. 28. Highland Climates <ul><li>Lower temperatures than lowlands at the same latitude </li></ul><ul><li>Variety of conditions based on: </li></ul><ul><ul><li>Elevation </li></ul></ul><ul><ul><li>Prevailing winds </li></ul></ul><ul><ul><li>Orientation of slope relative to the sun </li></ul></ul><ul><ul><li>Valley, slope, or peak </li></ul></ul><ul><ul><li>Ruggedness </li></ul></ul>
  29. 29. Climatic Change <ul><li>Long-term climatic change </li></ul><ul><ul><li>Significant variations over geologic time </li></ul></ul><ul><ul><ul><li>Ice ages </li></ul></ul></ul><ul><ul><ul><li>Medieval warm period and “little ice age” </li></ul></ul></ul><ul><ul><li>May be due to variations in: shape of Earth’s orbit, tilt of the axis, gyration of the rotation axis </li></ul></ul><ul><li>Short-term climatic change </li></ul><ul><ul><li>Natural processes </li></ul></ul><ul><ul><ul><li>Volcanic eruptions, oceanic circulation, sunspot activity </li></ul></ul></ul><ul><ul><li>Human processes </li></ul></ul><ul><ul><ul><li>Enhanced greenhouse effect </li></ul></ul></ul>
  30. 30. Climatic Change <ul><li>Greenhouse effect </li></ul><ul><ul><li>Certain gases in the atmosphere function as an insulating barrier, trapping infrared radiation </li></ul></ul><ul><li>Global warming </li></ul><ul><ul><li>Caused by human activities that have increased the amount of greenhouse gases in the atmosphere </li></ul></ul><ul><ul><ul><li>Carbon dioxide: burning fossil fuels, deforestation </li></ul></ul></ul><ul><ul><ul><li>Methane: natural gas and coal mining, agriculture and livestock, swamps, landfills </li></ul></ul></ul><ul><ul><ul><li>Nitrous oxides: motor vehicles, industry, fertilizers </li></ul></ul></ul><ul><ul><ul><li>Chlorofluorocarbons: industrial chemicals </li></ul></ul></ul>
  31. 31. Climatic Change <ul><li>Evidence of global warming </li></ul><ul><ul><li>20 th century was the warmest in 600 years </li></ul></ul><ul><ul><ul><li>Average surface temp rose over 1 ° F during the century </li></ul></ul></ul><ul><ul><li>Winter temps in the Arctic have risen about 7° F since the 1950s </li></ul></ul><ul><ul><ul><li>Loss of Arctic ice cap </li></ul></ul></ul><ul><ul><li>Glaciers are thinning and retreating </li></ul></ul><ul><li>Consequences of global warming include: </li></ul><ul><ul><li>Rising sea levels </li></ul></ul><ul><ul><li>Changes in temperature and precipitation patterns </li></ul></ul><ul><ul><ul><li>Impact on soils, vegetation, agriculture </li></ul></ul></ul>