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Temperature

Temperature. Temperature=average KE of molecules , or average speed of molecules: . Warm air is less dense, cool air is more dense. Temperature Scales. Kelvin scale. Based on absolute zero—temperature at which all motion stops -273 o C= -459 o F= 0 o K Centigrade (Celsius)

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Temperature

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  1. Temperature • Temperature=average KE of molecules, or average speed of molecules: Warm air is less dense, cool air is more dense

  2. Temperature Scales • Kelvin scale. Based on absolute zero—temperature at which all motion stops • -273o C= -459o F= 0o K • Centigrade (Celsius) • Water freezes at 0oC and boils at 100oC • Fahrenheit • Water freezes at 32oF and boils at 212oF…. • Converting oC to oF: Double the C temperature and then add 30…close ‘nuff most of the time oC*1.8 + 32=oF

  3. Influences on Temperature • Latitude • Altitude • Atmospheric circulation-weather • -clouds,wind • Contrasts between land and water • Warm and cold ocean currents • Local impacts on temperature

  4. LATITUDE—Remember how the seasons work Isotherms: Lines of equal temperature

  5. Latitude 23 Jun. 2007

  6. ALTITUDE Remember that temperature decreases with height in the troposphere Temp A > Temp B Temp C >Temp B Why?? C B A

  7. Daily temperatures & weather • When solar energy in > longwave energy out—temperature rises • Maximum occurs in late afternoon...clouds, haze, humidity, and ground cover control timing and maximum value • Minimum occurs just before sunrise Radiational Cooling Solar Heating

  8. Seasons (pp.43-50) Know and understand figure2-11 and 2-12 on p.44 September 22-23 March 21-22 December 21-22 June 21-22

  9. Summer solstice (N.H.)

  10. Autumnal (fall) and vernal (spring) equinoxes 12 hour day everywhere

  11. Equinox at the North Pole

  12. Winter Solstice (N.H.)

  13. Lag in seasonal temperatures • Most incoming radiation occurs on Jun 21st, but hottest air temperatures happen in July/Aug • Similar opposite case with winter solstice • Time lag caused by earth’s surface specific heat

  14. High latitudes lose more energy to space than they receive from sun each year—opposite in the lower latitudes • Energy transport must occur to balance

  15. Daily Temperature Variations • Daytime warming—begins as conduction in layer nearest warm ground • On a calm day, convection can’t influence the lowest portion of the air—can get temperature profile like this:

  16. Effects of winds on lower atmospheric temperatures Check out the wind Chill chart on Page 83! • Wind causes “forced convection”—much more efficient vertical transfer of heat • Therefore surface is cooler than expected as upper level cool air mixes with surface warm air

  17. Day – Night Radiation Differences • During day, the absorption gain from the sun’s short wave radiation is greater than the earth’s long wave radiation loss, so temperature rises. • During night, the earth’s long wave radiation loss is greater, so temperature falls.

  18. Radiation Inversion • Air temperature usually decreases with height (lapse rate) • At night, ground cools, and air near ground can become much cooler than air above—radiation inversion forms • Temperature increases with height—usually not much higher than 300 feet above the ground • Extremely stable conditions —fog often forms as air reaches Dew Point temperature • Long nights, calm winds, dry and cloud-free atmosphere are most favorable conditions for inversion formation

  19. Formation of Radiation Inversion How does the nighttime temperature profile change on a windy night?

  20. Impact of clouds on daily temperature During the nighttime, clouds Cause outgoing longwave radiation To be trapped. Therefore Temperature is warmer than on a Clear night. During the day solar radiation is blocked by clouds Therefore temperature is cooler at the surface than On a clear day.

  21. Land vs. coast Water holds heat longer therefore it heats up slower and cools down slower than The land. If you live near a large body of water, it will act like insulation. During the day, water will heat slowly And take heat away from the coastal City. During the night, water will release heat slowly and keep the coastal city warmer. Temp Ft. Walton Beach < Temp. Crestview Temp Ft. Walton Beach > Temp. Crestview

  22. Forecast: Cooler or Warmer?? • Daytime: Coastal city vs. Inland city? • Nighttime: Coastal city vs. Inland city? • Daytime: city with clear skies vs. city with cloudy skies • Nighttime: city with clear skies vs. city with cloudy skies • Daytime: city at 6,000ft vs. city at sea level • Nighttime: city at 300ft vs. city at sea level

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