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World Geography 3200

World Geography 3200. Chapter 4 Weather and Climate (pgs. 54-73). 1. Three main factors that affect both weather and climate. A. temperature B. moisture (precipitation) c. air movement (wind). 2. The Earth- Sun Relationship.

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World Geography 3200

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  1. World Geography 3200 Chapter 4 Weather and Climate (pgs. 54-73)

  2. 1. Three main factors that affect both weather and climate • A. temperature • B. moisture (precipitation) • c. air movement (wind)

  3. 2. The Earth- Sun Relationship • A. the earth rotates on it’s axis every 24 hours and it revolves around the sun every 365.25 days. • B(i). Equinox- is the two times duringthe yearwhen the sun shines equallyon both the Northern and Southern Hemispheres. ( Mar 20-23 and Sept 20-23) ( having a day andnight of equal length.

  4. B(ii). Solstices- is the time (June 21 or Dec22) at which the overhead Sun is farthest from the equator and appears tostand still before returning towardsthe equator . The longest day occurs at the summer solstice and the shortest day at the winter solstice.

  5. c. How does cloud cover affect the range of temperatures from day to night? • Clouds reduce the amount of solar radiation reaching the earth’s surface and also reduce the amount of heat radiated back into the atmosphere. • If there is no cloud cover , heating from the sun is strong during the day and heat loss is rapid at night. • This explains why there is a great difference between day and night temperature ranges when skies are clear.

  6. Conversely, on cloudy days , clouds block out sunlight during the day and keep in heat at night. • This explains why temperature ranges are more limited when we have cloud cover.

  7. Effects of Cloud Cover • on forecasted temperatures • During the day, the earth is heated by the sun. If skies are clear, more heat reaches the earth's surface (as in the diagram below). This leads to warmer temperatures.

  8. . However, if skies are cloudy, some of the sun's rays are reflected off the cloud droplets back into space. Therefore, less of the sun's energy is able to reach the earth's surface, which causes the earth to heat up more slowly. This leads to cooler temperatures.

  9. At night cloud cover has the opposite effect. If skies are clear, heat emitted from the earth's surface freely escapes into space, resulting in colder temperatures.

  10. However, if clouds are present, some of the heat emitted from the earth's surface is trapped by the clouds and reemitted back towards the earth. As a result, temperatures decrease more slowly than if the skies were clear.

  11. 3. Understanding the phenomenon of the seasons: • Seasons are directly related to the Earth’s revolution around the Sun . • Because of the tilt of the axis(23.5degrees), different places on the Earth’s surface experience different lengths of day and night on any one day. • Also, the intensity of the sun’s rays varies depending on the amount of atmosphere the rays pass through- when the sun is overhead , the Sun’s rays are most intense.

  12. Because the Earth revolves around the sun, the length of day and night and the intensity of the Sun’s rays change gradually because there is a gradual change in the way each hemisphere leans toward or away from the sun. • As the Earth revolves around the Sun, the seasons are characterized by gradual transitions from one to another as each hemisphere , receives more or less sunlight.

  13. The Seasons in the Northern Hemisphere The Seasons in the Southern Hemisphere

  14. 4. How does the Greenhouse Effect Moderate Climate • Animationhttp://www.sciencemuseum.org.uk/exhibitions/energy/site/EIZInfogr9.asp • The burning of fossil fuels produces certain gases (carbon dioxide ) that enter the atmosphere and absorb or trap heat within it.

  15. This trapping of the gases in the atmosphere causes temperatures to rise and the climates in all ecosystems of the world to become warmer.

  16. 5. Wind: The Movement of Air • Air generally flows from areas of high pressure to areas of low pressure • A. Wind – is the flow of air from an area of high pressure to one of low pressure • B. Prevailing Winds- is the major , constant winds blowing over the surface of Earth from high to low pressure areas.

  17. 6. Orographic ( Relief) Rainfall • caused by abrupt changes in relief, air masses rise up mtns. (refer to fig. 4.13 pg. 66) • Animationhttp://www.classzone.com/books/earth_science/terc/content/investigations/es1806/es1806page03.cfm?chapter_no=investigation

  18. A. Air is forced to rise because it is deflected upward by the high mountains • B. As the air rises , it cools and it’s ability to hold moisture lessens(condensation occurs) • C. By the time the air reaches the highest point on the mountain, it has lost most of it’s water vapour it picked up over the ocean

  19. D. The air begins to descend down the inland (leeward) side of the mountain, it compresses and becomes warmer. • The relative humidity of the air lowers , having a drying effect. • ( Rain Shadow – is an area of relatively low rainfall on the leeward side of the uplands)

  20. 7. Frontal Precipitation • Occurs when a front is created on the meeting of two air masses with different temperatures. (Refer to fig.4.14 p.66) • Animationhttp://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/cold_front_precip.rxml?hret=/guides/crclm/act/fpr.rxml&prv=1

  21. A. As warm moist air comes in contact with colder air , it is forced to rise up over the colder air because the colder air is denser and heavier than the warm air. • B. As the warm moist air rises, it becomes cooler.

  22. C. As the warm air cools, the relative humidity rises, to the point at which the air mass can no longer hold the water vapour it brought from the ocean. This water vapour condenses and falls as precipitation.

  23. 8. Convectional Rainfall • Occurs when a convection cell develops , causing warm moist air to rise.( Refer tofig. 4.15 p.67)

  24. A. The air immediately above the heated land surface warms up and consequently rises. Cool air flows in from above and from the sides to replace rising warm air. This creates a convectional flow. • B. This type of precipitationtypically occurs in the summer in mid –to late afternoon after a day of high rising temperature.

  25. C. Lightning and thunder often accompany this type of precipitation because the air flows quite rapidly and intensely. These vigorous air movements cause considerable friction between the air molecules.

  26. 9. Ocean Currents and Climate • Ocean Currents - are permanent or semi-permanent horizontal movement of unusually cold or warm surface water of the oceans, to a depth of about 100m.

  27. Three main factors that influence how and where ocean currents flow: • A. Like wind systems, ocean currents are affected by the Coriolis Effect. They shift right or left depending on the hemisphere where they are found. • B. Ocean currents are affected by the size and shape of the body of water in which they develop . Gulf stream is deflected to the north and east by the shape of the North American coastline.

  28. C. Ocean currents are influenced by differences in water temperature and salt content. They cause convection currents to develop.

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