Transcript ATMO 201: Atmospheric Science

CHAPTER 3
TEMPERATURE AND
ENERGY BALANCE
The sky appears blue because gases and particles in the atmosphere
scatter some of the incoming solar radiation in all directions. Air molecules
scatter shorter wavelengths most effectively. Thus, we perceive blue light,
the shortest wavelength of the visible portion of the spectrum.
Sunrises and sunsets appear red because sunlight travels a longer path
through the atmosphere. This causes a high amount of scattering to remove
shorter wavelengths from the incoming beam radiation. The result is sunlight
consisting almost entirely of longer (e.g., red) wavelengths.
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Each day is like a tiny
season!
◦ Daytime heating,
nighttime cooling
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Why do the high and
low temperatures
happen when they do?
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Daily temperature
range near the
ground is much
greater than that
above the ground!
The daily mean is defined as the average of the
maximum and minimum temperature for a day.
The daily temperature range is obtained by
subtracting the minimum temperature from the maximum.
The monthly mean temperature is found by
summing the daily means and dividing by
the number of days in the month.
The annual mean temperature is obtained by
summing the monthly means for a year and dividing by 12.
The annual range is obtained as the difference
between the highest and lowest monthly mean temperatures.
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Latitude
Land and water distribution
Ocean currents
Elevation
Fig. 3.15, p. 78
Tale of three cities
Fig. 3.14, p. 77
Fig. 3.8, p. 70
Fig. 3.4, p. 66
Fig. 3.5, p. 67
Fig. 3.9, p. 71
Fig. 3.10, p. 72
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Even with the same
average temperature,
the range can differ
considerably
Why might these be so
different?
____
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Which curve
is Juneau and
which is
Edmonton?
Why are they
different?
________________
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(Note: these are kind of confusing!)
“Average temperature”: the average of the
high and low temperature for the day
“Normal temperature”: a 30-year average
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“Degree days”
When average temperature (average of high
and low) is above 65 degrees F, people tend
to use air conditioning
◦ “Cooling degree days”
◦ Each degree above 65 = one cooling degree day
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When average temperature is below 65
degrees F, people tend to heat their
homes/offices
◦ “Heating degree days”
◦ Each degree below 65 = one heating degree day
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When average temperature is above the
base growing temperature for a crop
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Body’s Perception: Sensible temperature
◦ How we exchange heat energy with environment
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Wind and cold
◦ Body, like the planet, must also have a heat/energy
balance if temperature is to be maintained.
◦ Thin layer of warm molecules next to skin
 Wind interferes with this, rapidly removes heat
◦ Sensible temperature for cold weather: Wind Chill
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Frostbite: Skin actually freezes and discolors
Cold, Damp Weather
◦ A cold rainy day often feels colder than a “dry” one
because water on exposed skin conducts heat away
from the body better than air does
◦ Hypothermia – body temp drops below normal
 Most hypothermia occurs between freezing and 50° F,
snow vs. rain, the wet really matters!
 “Died of Exposure”
Dew Point
(usually a better way to compare humidity)
Fig. 3.20, p. 83
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