Temperature

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Temperature

  1. 1. + Temperature Chapter 3Copyright © 2013 Pearson Education, Inc.
  2. 2. + 3.1 For the Record: Air Temperature DataCopyright © 2013 Pearson Education, Inc.
  3. 3. + For the Record: Air-Temperature Data  Basic calculations:  Daily mean  Monthly mean  Average of 24 hourly  Average of daily means readings  Annual mean  Daily temperature range  Average of monthly means  Difference of daily  Annual temperature range high and low  Difference of highest and lowest monthly meanCopyright © 2013 Pearson Education, Inc.
  4. 4. + For the Record: Air-Temperature Data Isotherms:  Lineconnecting equal temperature  Generally there is a 5° to 10° temperature change per unit of difference Closely spaced isotherms indicate rapid temperature changes Wider spaced isotherms indicate a more gradual rate of changeCopyright © 2013 Pearson Education, Inc.
  5. 5. +Copyright © 2013 Pearson Education, Inc.
  6. 6. + 3.2 Why Temperatures Vary: The Controls of TemperatureCopyright © 2013 Pearson Education, Inc.
  7. 7. + Why Temperatures Vary: The Controls of Temperature Controls of temperature:  Differential heating of land and water  Ocean currents  Altitude  Geographic positioning  Cloud cover and albedoCopyright © 2013 Pearson Education, Inc.
  8. 8. + 3.3 Land and WaterCopyright © 2013 Pearson Education, Inc.
  9. 9. + Land and Water Why do they cool differently? Water is mobile.  Temperatures rise and fall slower on water than on land. Land is opaque.  Heat is absorbed only on the surface. Specific heat is three times greater for water than land. Evaporation is greater over water.Copyright © 2013 Pearson Education, Inc.
  10. 10. + 3.4 Ocean CurrentsCopyright © 2013 Pearson Education, Inc.
  11. 11. + Ocean Currents  At the water surface energy is passed from moving air to the water through friction. The drag exerted by winds blowing steadily across the ocean causes he surface layer of water to move.  Minor horizontal movements of surface water are closely related to the circulation of the atoms, which in turn is driven by the unequal heating of earth by the sun.Copyright © 2013 Pearson Education, Inc.
  12. 12. +Ocean Currents The transfer of heat by winds and ocean currents equalize these latitudinal energy imbalancesCopyright © 2013 Pearson Education, Inc.
  13. 13. + 3.5 AltitudeCopyright © 2013 Pearson Education, Inc.
  14. 14. + Altitude Temperatures decrease with altitude. The atmosphere is thinner at higher altitudes. Higher altitudes produce a greater daily temperature range.Copyright © 2013 Pearson Education, Inc.
  15. 15. + 3.6 Geographic PositionCopyright © 2013 Pearson Education, Inc.
  16. 16. + Geographic Position Windward coast  Costal location where prevailing winds blow from the ocean onto the shore Leeward coast  Costal location where prevailing winds blow from land toward the ocean Mountains can cut off the ocean winds and give cities more continental temperaturesCopyright © 2013 Pearson Education, Inc.
  17. 17. + Geographic PositionCopyright © 2013 Pearson Education, Inc.
  18. 18. + 3.7 Cloud Cover and AlbedoCopyright © 2013 Pearson Education, Inc.
  19. 19. + Cloud Cover and Albedo More clouds cause lower surface temperatures during the day, but warmer temperatures at night. A high albedo reduces surface temperature.  Clouds have high albedos, so incoming solar radiation gets bounced back to space. So by reducing incoming solar radiation, day temps will be lower than if clouds were absent.Copyright © 2013 Pearson Education, Inc.
  20. 20. + Cloud Cover and Albedo Snow acts like clouds  Sunny days are cooler because energy the land would have absorbed and used for heating the air is reflected and lost.Copyright © 2013 Pearson Education, Inc.
  21. 21. + 3.8 World Distribution of TemperaturesCopyright © 2013 Pearson Education, Inc.
  22. 22. + World Distribution of Temperature There is a smaller temperature range at the equator. There is a larger temperature range at higher latitudes. Interiors of continents have a higher temperature range. Coastal regions have a smaller temperature range.Copyright © 2013 Pearson Education, Inc.
  23. 23. + World Distribution of Temperature There are also latitudinal shifting of temperatures caused by seasonal migration of the sun  Look at colors on figures 3.18 and 3.19 Isotherms in Southern Hemisphere are much more regular than in Northern Hemisphere.Copyright © 2013 Pearson Education, Inc.
  24. 24. + Figure 3.18 pg. 78Copyright © 2013 Pearson Education, Inc.
  25. 25. + Figure 3.19 pg. 78Copyright © 2013 Pearson Education, Inc.
  26. 26. + 3.9 Cycles of Air TemperatureCopyright © 2013 Pearson Education, Inc.
  27. 27. + Cycles of Air Temperatures Daily temperature variations:  Primary control of the daily cycle of air temp is earth’s daily rotation causing periods of light and dark.  At noon time incoming rays exceed outgoing equal a surplus for a few hours. When the input is no longer exceeds the rate of energy lost by Earth the temperature falls.  Vary by seasons.  Vary with cloud cover.Copyright © 2013 Pearson Education, Inc.
  28. 28. + Cycles of Air TemperaturesCopyright © 2013 Pearson Education, Inc.
  29. 29. + Cycles of Air Temperatures Magnitude of daily temperature change:  At mid and low latitudes, a high sun angle results in a large variation throughout the day.  At higher latitudes, a low sun angle results in lower temperature variations.  Windward coasts have small variations.  Inland areas have larger variations.  Temperature change depends on the amount of cloud cover and water vapor.Copyright © 2013 Pearson Education, Inc.
  30. 30. + Cycles of Air Temperatures Annual temperature variations:  Highest and lowest mean temperatures do not coincide with maximum or minimum incoming solar radiation.  In the northern hemisphere, August has the highest mean temperature, while June has the highest incoming solar radiation.Copyright © 2013 Pearson Education, Inc.
  31. 31. + 3.10 Temperature MeasurementsCopyright © 2013 Pearson Education, Inc.
  32. 32. + Temperature Measurement Mechanical thermometers:  Liquidin glass  Maximum thermometer—mercury  Minimum thermometer—alcohol  Thermograph—bimetal strip Electrical thermometers:  Thermistor—electrically resistant at different temperatures  Very fastCopyright © 2013 Pearson Education, Inc.
  33. 33. + Temperature Measurement Instrument shelters:  White box  Louvered sides  Over grass  1.5 m above groundCopyright © 2013 Pearson Education, Inc.
  34. 34. + 3.11 Temperature ScalesCopyright © 2013 Pearson Education, Inc.
  35. 35. + Temperature Scales Fixed points:  Ice point  Ice melts  32° F, 0° C, 273 K  Steam point  Water boils  212° F, 100° C, 373 KCopyright © 2013 Pearson Education, Inc.
  36. 36. + Temperature Scales °F = (1.8 x °C) + 32 °C = (°F-32)/ 1.8Copyright © 2013 Pearson Education, Inc.
  37. 37. + 3.12 Heat Stress and Wind ChillCopyright © 2013 Pearson Education, Inc.
  38. 38. + Heat Stress and Wind Chill: Indices of Human Discomfort Apparent temperature is the temperature a person perceives. Heat stress is caused by high temperature and high humidity.  Sweat does not evaporate from body.  Feels hotter  Heat stress indexCopyright © 2013 Pearson Education, Inc.
  39. 39. + Heat Stress and Wind Chill: Indices of Human DiscomfortCopyright © 2013 Pearson Education, Inc.
  40. 40. + Heat Stress and Wind Chill: Indices of Human Discomfort  Wind chill is the cooling power of moving air.  Evaporates moisture  Cools body thus feel colder  Wind chill chart  Calculates how the wind and cold feel on human skin  A calm sunny winter day feels warmer because the warm feeling is caused by the absorption of direct solar radiation by the bodyCopyright © 2013 Pearson Education, Inc.
  41. 41. + Heat Stress and Wind Chill: Indices of Human DiscomfortCopyright © 2013 Pearson Education, Inc.

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