Chapter 17
The Atmosphere:
Structure and Temperature
Section 17.3
Temperature Controls
Temperature
Controls
Why Temperatures Vary
• Temperature is one of the basic elements of
weather and climate.
• A temperature control is any factor that
causes temperature to vary from place to
place and from time to time.
• Factors that exert a strong influence on
temperature are:
– Latitude, heating of land and water, altitude,
geographic position, cloud cover, and ocean
currents.
Temperature
Controls
Why Temperatures Vary
• Because variations in the angle of the sun’s
rays and length of daylight depend on latitude,
they are responsible for warmer temperatures
in the tropics and colder temperatures
towards the poles.
• Seasonal temperature changes happen as
the sun’s vertical rays move toward and away
from a particular latitude during the year.
Question:
Which of the following is NOT a factor that
controls temperature?
A. Longitude
B. Cloud cover
C. Ocean currents
D. Altitude
Temperature
Controls
Land and Water
• Land heats more rapidly and to higher temperatures
than water.
• Land also cools more rapidly and to lower temperatures
than water.
• Temperature variations are considerably greater over
land than over water.
– Example: Vancouver has moderate temps compared to
Winnipeg due to the proximity to the Pacific Ocean.
– Ex: Water accounts for 61% of the Northern Hemisphere
and land accounts for the remaining 39%. In the Southern
Hemisphere, 81% of the surface is water and only 19% is
land. The Southern Hemisphere shows smaller annual
temperature variations.
Land & Water
Mean Monthly
Temperatures
for Vancouver
and Winnipeg
Temperature
Controls
Geographic Position
• Geographic settings also play a large role in
temperature variations.
– A coastal location where prevailing winds blow from the
ocean onto shore (windward coast) experience full
moderating influence of the ocean – cool summers and
mild winters.
– A coastal location where the prevailing winds blow from
the land to the ocean (leeward coast) will have a more
continental temperature pattern.
– Example: Eureka, CA is more moderate due to a
windward coast compared to NY,NY that has more
extreme temps due to the leeward coast.
Temperature
Controls
Mean Monthly
Temperatures
for Eureka and
New York City
Temperature
Controls
Geographic Position
• Mountain ranges also effect temperature
variations, as they act as barriers.
– Mountain ranges cut off the moderating influence
of the oceans, thus making those on the
windward side of the mountains have more of a
marine influence and those on the leeward side a
more continental influence.
– Example: Spokane has more extreme temp. than
Seattle due to the Cascade Mts cutting off the
influences of the Pacific Ocean.
Temperature
Controls
Mean Monthly
Temperatures
for Seattle and
Spokane
Temperature
Controls
Altitude
• Altitude is another temperature control.
• The higher the altitude, the cooler the
temperatures.
• The lower the altitude, the higher the
temperatures.
• This is caused by having more or less
atmosphere.
• Example: Quito, Ecuador is cooler than
Guayaquil due to its altitude.
Temperature
Controls
Mean Monthly
Temperatures
for Guayaquil
and Quito
Temperature
Controls
Cloud Cover and Albedo
• Cloud cover also greatly effects temperature.
• Many clouds have a high albedo, and therefore reflect a
significant portion of the sunlight that strikes them back
to space.
– Albedo: The fraction of total radiation that is reflected by
any surface.
• By reducing the amount of incoming solar radiation, the
maximum temperatures on a cloudy day will be lower
than on a cloudless day.
• The opposite is true during the night where clouds act as
a blanket by absorbing outgoing radiation emitted by the
Earth and reradiating it back to the surface.
Temperature
Controls
Clouds Reflect and Absorb Radiation
Question:
Vancouver, British Columbia, enjoys a
moderate year-round climate, which is due to
A. The many mountain ranges surrounding the
city.
B. Its latitude.
C. Its relatively high elevation.
D. Its close proximity to the Pacific Ocean.
Question:
The temperature differences seen between
Seattle, Washington, and Spokane,
Washington, illustrate the effect of
A. Cloud cover.
B. Geographic position.
C. Altitude.
D. Ocean currents.
Question:
The temperature differences between Quito,
Ecuador, and Guayaquil, Ecuador, illustrate the
effect of
A. Cloud cover
B. Geographic position.
C. Altitude.
D. Ocean currents.
Question:
What causes clouds to reflect a portion of
sunlight back to space?
A. The amount of oxygen in the atmosphere
B. Evaporation from the land
C. Temperature differences between the land
and the atmosphere
D. A characteristic known as albedo
Question:
Clouds absorb outgoing radiation emitted by
Earth and reradiate a portion of it back to the
surface during
A. Nighttime.
B. Daytime.
C. Summer.
D. Times of heavy rainfall.
Temperature
Controls
World Distribution of Temperature
• Isotherms are lines that connect points that
have the same temperature.
– From hot colors near the equator to cool colors
towards the poles.
– Isotherms show a general trend of temperatures
of land and water, changes in latitude, and ocean
currents.
– Isotherms generally trend east to west and show
a decrease in temperatures from the tropics
towards the poles.
Question:
Which of the following is a general trend on a
world isothermal map?
A. Temperatures decrease from east to west.
B. Isotherms become wider closer to the poles.
C. There are more isotherms closer to the
equator.
D. Temperatures decrease from the tropics
toward the poles.