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TEMP

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					            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
  – -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
Influences on Temperature


1. Latitude
2. Altitude
3. Atmospheric circulation-weather
        -clouds,wind
4. Contrasts between land and water
5. Warm and cold ocean currents
6. Local impacts on temperature
LATITUDE—Remember how the seasons work




                              Isotherms: Lines of equal
                              temperature
Latitude




           23 Jun. 2007
                         ALTITUDE

Remember that temperature decreases with height in the troposphere




                                   Temp A > Temp B
     C               B
                                   Temp C >Temp B

                                   Why??


                     A
          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
     Solar
                 Cooling
     Heating
                 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
Summer solstice (N.H.)
Autumnal (fall) and vernal (spring)
           equinoxes



                         12 hour day everywhere
Equinox at the North Pole
Winter Solstice (N.H.)
 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
• 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
  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:
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
       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.
          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
      Formation of Radiation
           Inversion




How does the nighttime temperature profile change on a windy night?
               Impact of clouds on daily temperature




                                                      During the nighttime, clouds
During the day solar radiation is blocked by clouds
                                                      Cause outgoing longwave radiation
Therefore temperature is cooler at the surface than
                                                      To be trapped. Therefore
On a clear day.
                                                      Temperature is warmer than on a
                                                      Clear night.
                                 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           During the night, water will release heat
   And take heat away from the coastal              slowly and keep the coastal city warmer.
   City.
Temp Ft. Walton Beach < Temp. Crestview        Temp Ft. Walton Beach > Temp. Crestview
        Forecast: Cooler or Warmer??

1. Daytime: Coastal city vs. Inland city?
2. Nighttime: Coastal city vs. Inland city?
3. Daytime: city with clear skies vs. city with cloudy skies
4. Nighttime: city with clear skies vs. city with cloudy skies
5. Daytime: city at 6,000ft vs. city at sea level
6. Nighttime: city at 300ft vs. city at sea level

				
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posted:10/3/2011
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