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The Sun: Our Heat Source


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The Sun: Our Heat Source

  1. 1. The SunOur Heat Source
  2. 2. Insolation Insolation is incoming solar radiation that heats our planet. Round surface of Earth + 23.5° tilt on axis = differential heat distribution
  3. 3. Insolation and Latitude
  4. 4. Absorption vs Reflection  Albedo: % of solar radiation reflected back into space Light surfaces = high  Dark surfaces = high albedo absorption  Causes uneven (differential) heating of Earth’s surface
  5. 5. Albedo
  6. 6. Lapse Rate A drop in temperature as altitude (or elevation) increases -1°C for every 150m in elevation Air is heated by the Earth’s surface, not by the Sun
  7. 7. Lapse Rate and Altitude
  8. 8. Temperature and Altitude
  9. 9. Aspect The compass direction a slope is facing In the Northern hemisphere…  South-facing slopes get more sunlight
  10. 10. Aspect
  11. 11. Solar Energy Received• Although the greatest intensity of solar radiation occurs at the time of the summer solstice, in the Northern Hemisphere the months of July and August are generally the warmest of the year.• Conversely, in the Northern Hemisphere a minimum of solar energy is received in December at the time of the winter solstice, but January and February are usually colder.
  12. 12. Varying Temperatures hot cold water solidConvective heat transfer Conductive heatallows for deeper mixing transfer is shallow(more efficient) (less efficient)
  13. 13. Specific Heat of Various Substances 4.5 Specific Heat: The amount of heat needed to 4 raise the temperature of a substance 1deg C. Because the specific heat is much greater for 3.5 water than for land it takes more energy to warm Hg water than it does land. 3 CuSpecific Heat Fe 2.5 SiO2 2 CaCO3 O2 1.5 Land 1 H2O 0.5 0 Hg Cu Fe SiO2 CaCO3 O2 Land H2O Substances Specific heat: the heat (heat energy) need to raise the temperature of one gram of a substance 1° C. The higher the heat capacity the more energy needed to raise the temperature of that substance.
  14. 14. Varying Temperatures Water  Land  Heat can penetrate  Denser deeper  Heats quickly, but only  Water moves = mixing to a shallow depth and spreading of heat  At night, cools quickly  At night, retains much  Inland locations of the heat  Summer = hot  Coastal locations  Winter = cold  Summer = moderate  Winter = moderate
  15. 15. Temperature• Temperature is one of the most basic elements of weather and climate.• The daily mean temperature is determined by averaging the 24 hourly readings or by adding the maximum and minimum temperatures for a 24-hour period and dividing by two.• The daily temperature range is computed by finding the difference between the maximum and minimum temperatures.• Other temperature data: • monthly mean temperature • annual mean temperature • annual temperature range
  16. 16. Temperature Scales• The three common temperature scales used to measure temperature are: • (1) the Fahrenheit scale, which is defined by using the ice point (32°) and steam point (212°), • (2) the Celsius scale, a decimal scale on which the melting point of ice is set at 0 and the boiling point of water at 100°, and • (3) the Kelvin or absolute scale, where the zero point represents the temperature at which all molecular motion is presumed to cease (called absolute zero), the ice point is set at 273, and the steam point at 373.
  17. 17. Human Perception of Temperature• The heat stress index (or heat index), a commonly used expression of summertime discomfort, links humidity and temperature to determine the thermal comfort of the human body.• Wind chill, a typical wintertime index, uses both wind and air temperature to calculate the human sensation of temperature.
  18. 18. Warm Ocean Currents
  19. 19. Earth’s Energy Budget Balance between incoming solar radiation and outgoing infrared radiation Solar Radiation  Infrared Radiation  Incoming  Outgoing  Shortwave  Longwave  Heats our planet  Lost to outer space
  20. 20. Energy Budget
  21. 21. Distribution of Heat Warm land or water bodies heats air above Warm air rises (Convection) = low air pressure Cold air sinks = high air pressure Wind = air pushing from high to low pressure areas Water moves heat in the same manner
  22. 22. WIND
  23. 23. Urban Heat Island
  24. 24. Urban Heat IslandAtlanta, Georgia