chapter 3 temperature and energy balance

CHAPTER 3

TEMPERATURE AND ENERGY BALANCE

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 paththrough the atmosphere. This causes a high amount of scattering to removeshorter wavelengths from the incoming beam radiation. The result is sunlight

consisting almost entirely of longer (e.g., red) wavelengths.

Each day is like a tiny season!◦ Daytime heating,

nighttime cooling Why do the high and

low temperatures happen when they do?

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 bysubtracting the minimum temperature from the maximum.

The monthly mean temperature is found bysumming the daily means and dividing by

the number of days in the month.

The annual mean temperature is obtained bysumming the monthly means for a year and dividing by 12.

The annual range is obtained as the differencebetween the highest and lowest monthly mean temperatures.

Latitude Land and water distribution Ocean currents Elevation

Fig. 3.15, p. 78

Fig. 3.14, p. 77

Tale of three citiesTale of three cities

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

Even with the same average temperature, the range can differ considerably

Why might these be so different?

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

“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

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

When average temperature is above the base growing temperature for a crop

Body’s Perception: Sensible temperature◦ How we exchange heat energy with environment

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

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”

Fig. 3.20, p. 83

Dew PointDew Point (usually a better way to compare humidity)(usually a better way to compare humidity)

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