2. CLIMATE UNIT

3. I. Definitions

4. s A. Weather--day by day variations in temperature (temp), winds,pressure and precipitation (ppt)

5. s B. Climate--average seasonal weather for an area, usually described in terms of monthly averages of temp and ppt.

6. Before we can study about weather and climate we need to know a little about Earth movements and Earth/Sun relations.

7. II. Earth Movements & Earth/Sun Relations

8. s A. Rotation s 1. The earth rotates on its axis.

9. s 2. It takes 24 hours to make one complete rotation.

10. s 3. Therefore, when we look at rotation we can talk about day and night and time zones.

11. s B. Revolution s 1. The earth revolves around the sun.

12. s 2. It takes approx. 365 days to make one complete revolution.

13. s 3. Therefore, when we look at revolutions of Earth around the sun we can explain seasons.

14. See diagrams and handout.

15. North Pole South Pole Equator Tropic of Cancer Tropic of Capricorn Circle of Illumination Arctic Circle Antarctic Circle

16. North Pole South Pole Equator Tropic of Cancer Tropic of Capricorn Circle of Illumination Arctic Circle Antarctic Circle

17. North Pole South Pole Equator Tropic of Cancer Tropic of Capricorn Arctic Circle Antarctic Circle Circle of Illumination

18. III. Climate Elements s A. Temperature (temp.)--the amount of heat in the atmosphere.

19. s B. Precipitation (ppt)-- the falling moisture onto the earth, rain, snow, sleet, hail, fog, etc.

20. s C. Air Pressure & Wind

21. s 1. Air Pressure--is the weight of the air (the air being forced down or let up.)

22. s 2. Wind--horizontal movement of air.

23. ******************************* The climate controls act upon the elements to produce different climates. ******************************

24. IV. Climate Controls s A. Latitude

25. s 1. Low Latitudes or Tropics

26. s a. Area between the Tropic of Cancer and Tropic of Capricorn (it actually extends a little north and south to 30N and 30S).

27. s b. Tend to be warm to hot year round. s c. Where the sun’s rays are perpendicular

28. Low Latitudes 30 N 30 S 0

29. s 2. Middle Latitudes or Temperate Region s a. 30 to 60 North and 30 to 60 South

30. s b. Neither hot nor cold--will get cold part of the year and hot part of the year. s c. Has seasons

31. Middle Latitudes Low Latitudes Middle Latitudes 60 N 30 N 30 S 60 S 0

32. s 3. High Latitudes or Polar Regions s a. 60 to 90 North and South

33. s b. The sun is never directly overhead and with the times of darkness it gets very cold.

34. High Latitudes Middle Latitudes Low Latitudes Middle Latitudes High Latitudes 90 N 90 S 60 N 30 N 30 S 60 S 0

35. Cold all year Seasons Hot all year

36. s B. Continentality

37. s 1. In general, large land masses will have greater changes in temp.

38. s 2. Land will get hotter and colder depending on the temp. of the air.

39. s 3. Large bodies of water stay relatively the same temp. all year.

40. s 4. Therefore, if wind crosses over water to get to a place it will stay relatively the same temp. all year.

42. s If it crosses over land there will be greater variations of temperature change.

44. s C. Elevation

45. s 1. The higher up a mountain you go--the cooler it gets.

46. s 2. For every 1000’ the temp.drops 3.6 F.

47. s 3. Therefore, in highland areas the temp. will vary depending on where you are on the mountain side.

48. A B C D E F G H I J K

49. s D. Atmospheric Circulation s 1. General Facts

50. s a. The Low Lat. receive more heat.

51. s b. Heat is transmitted to the higher lat. by ocean currents & atmospheric circulation.

52. s 2. Pressure Systems

53. s a. Because of uneven heating, areas of high and low pressures develop.

54. s 1) Low Pressure

55. s a) Where the earth is relatively hot the atmosphere is heated causing the surface air to expand and rise.

56. s b) i.e. Heated air rises--expands and is less dense--low pressure.

57. L H H 30 N 0 30 S Hadley Cell

58. s 2) High Pressure s a) As the air cools it becomes more dense.

59. s b) Air begins to sink--High Pressure

60. 30 N 0 30 S L H H 60 N 60 S L L

61. s b. Air moves from a High Cell to a Low Cell along the surface of Earth.

62. s c. As the air moves parallel to Earth wind systems develop.

63. s d. Because of Earth’s rotation the winds are deflected to the left in both the Northern Hem. & the Southern Hem.

64. Coreolis Effect

65. s e. Therefore, air moving out of a High Cell in the Northern Hem. is clockwise & counterclockwise in the Southern Hem.

66. s f. As the air moves into a Low Cell it is counterclockwise in the Northern Hem. & clockwise in the Southern Hem.

67. H L Northern Hemisphere

68. H L Southern Hemisphere

69. Northern Southern Hem. Hem. High CellCWCCW Low Cell CCW CW

70. s g. High Pressure Cells -- stable weather conditions, clear, dry (no ppt.)

72. s h. Low Pressure-- unstable, rainy, windy. (hurricanes,typhoons, cyclones,tornadoes, willy willies, etc.)

74. s 3. Wind Belts s a. Out of the High Cells we get winds as the air moves to a Low Cell.

75. s b. In a Low cell the air is rising-- no wind.

76. s c. In a High cell the air is sinking-- no wind.

77. s d. Winds are named from where they come. --See diagram.

78. Westerlies NE Trades SE Trades 0 30 S 60 S 30 N 60 N Horse Latitudes Doldrums

79. s 4. Air Masses s a. Independent of the wind systems, masses of air move into an area.

80. s b. Each has its own temp. & ppt. characteristics.

81. s 1) Warm Masses, Cold Fronts, etc. s 2) Marine vs. Continental Air Masses.

82. s c. Fronts are places where a mass of warm air meets a mass of cold air.

83. When they meet-- clouds and ppts. occur. Usually clear afterwards.

84. Dry s High Cell--Dry Wet s Low Cell--Wet

85. s E. Ocean Circulation s 1. Ocean currents help move the heat from the equator to the poles.

86. s 2. Ocean Currents are clockwise in the N. hemisphere and counterclockwise in the S. hemisphere.

87. s 3. Each current is considered a warm, hot, cool or cold current depending on where it is. s 4. See Map.

88. 4 1 3 3 1 2 6 5 7 8 11 9 10 12 13 14 15 16

89. s 5. In general, s a. Warm currents: along the equator s b. Hot currents: W side of ocean E side of continents

90. s c. Cool currents: near Arctic and Antarctic circles s d. Cold currents: E side of ocean W side of continents

91. s 6. Moisture is not picked up from a cold current. It will be picked up from a hot current.

92. Wet s Hot Current--Wet Dry s Cold Current--Dry

94. s F. Mountain Barriers

95. s 1. Barriers will block the winds and funnel them in different areas

96. s a. Rocky Mts. funnel the winds through the Great Plains and block south California

97. s b. The Alps block cold air from the north keeping N. Italy warm

98. s c. The Himalayas keep India warm s d. etc.

99. s 2. Orographic ppt.

100. Warm, moist air Dry air wet Windward-- wet dry Leeward-- dry Dew Point

101. s a. Deserts can result on the leeward side (Atacama Desert)

102. s b. Rainy on the windward side (Washington & Oregon--windward of the Cascade Mts.)

104. 1 2 3 5 4 6 7 8 9 10