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Lecture 4

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Lecture 4

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  1. Lecture 4 More about Temperature

  2. Incoming vs. Outgoing Radiation

  3. Controls of Temperature • Latitude • Land and Water • Ocean Currents • Elevation

  4. Average Temperature in January

  5. Average Temperature in July

  6. Contouring EXAMPLE

  7. Contouring

  8. Contouring

  9. Daytime Warming On a clear, windless day, joggers may experience a temperature of 122oF near their feet, and a temperature of 90oF near their waist.

  10. Daytime Warming

  11. Peak Temperature

  12. Nighttime Cooling

  13. Radiation Inversion Ingredients • Windless night • Wind mixes the air with turbulent eddies • A long night • Cloudless night • Clouds radiate infrared energy back to surface • A dry night • If dew forms, then latent heat of condensation is released.

  14. Radiational Inversion

  15. Daily Low Temperature • The lowest temperature may be reached after sunrise. Why? • After sunrise outgoing energy still exceeds incoming. • The solar angle is low at sunrise • If there is moisture, then evaporation cools the air.

  16. Peak Temperature

  17. How do we protect crops from freezing?

  18. How do we protect crops from freezing?

  19. Diurnal Range

  20. Heating Degree-Day

  21. Cooling Degree-Day

  22. Growing Degree-Day

  23. Mean Annual Temperature

  24. Measuring Temperature

  25. Measuring Temperature • Liquid in Glass Thermometers (mercury or alcohol) • Electric Thermometers (used in Automated Weather Stations) • Thermocouples • Platinum Resistance Thermometers • Radiometers (on satellites, weather balloons) • Bimetallic Thermometer (thermographs)

  26. Wind Chill Why doe the wind make it feel colder? • On cold days our body warms a thin layer of air around us. • When the wind blows, this warm layer is replaced by cold air. • The faster the wind blows the colder we feel.

  27. The wind chill equivalent temperature tells us how cold it would have to be with no wind, in order for us to lose the same amount of heat. • This is new as of 2001! • - Replaces Paul Siple’s original work in Antarctica • - A bit “warmer” than the old formula • -Will be updated in the near future for sunshine

  28. Controls of Temperature • Latitude • Land and Water • Ocean Currents • Elevation

  29. Urban Heat Island Stanley Park Downtown Vancouver

  30. Urban Heat island • Decrease in: • Wind speed • Humidity (drainage systems take away water!) • Increase in: • Temperatures • Cloudiness • Precipitation • Fog • Pollution

  31. Causes of Urban Heat Island • Surfaces • Low albedos of asphalt and concrete • Heat trapping • Tall structures reflect and absorb outgoing radiation • Lack of water (rapid water run-off) • Less water  less evaporative cooling • Surface friction • Low wind speed  less mixing

  32. Causes of Urban Heat Island • Human produced heat • In buildings, automobiles • Particulates and Smog • Greenhouse enhancer, traps heat • Snow Removal • Decreases the albedo

  33. Heat Island Example Areas that are “warm” appear in white/light gray. Areas that are “cool” appear dark. Atlanta

  34. Heat Island Example Trees and vegetation appear in red. Buildings, streets and urban land cover is white/blue-green/black. Note the shape of the downtown region. Atlanta

  35. Heat Island Example Remember the shape of the downtown!

  36. Heat Trapping