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Climate Controls
Why does temperature vary so much in the world?
The answer: PSALMON
1)
Prevailing Winds:
High pressure (think of a bulldozer pushing down the air)-keeps air close to the
ground it does not rise-therefore dry conditions
Low pressure the air rises, as it rises it cools, condenses (clouds), and precipitation
happens.
At 0 degrees-Low Pressure
30 degrees-High Pressure
60 – Low Pressure
90-High pressure
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In
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2) Slope of the Land
Direction a slope faces
the northern hemisphere:
south facing slopes are drier (more sunshine)
north facing slopes are wetter and have less sun
3) Altitude: the higher you go up, the colder it gets.
Why? Less dust, greenhouse gases, water vapour, etc. to trap heat coming up
from the earth's surface.
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As elevation increases – temperature decreases (think of going up a mountain)—1
degrees for every 150 meters of elevation.
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Air becomes thinner cannot conserve (keep) heatthat is why pressure decreases
with elevation.
4) Latitude: the further north you go in the northern
hemisphere, the colder it gets.
Why?
a) Curvature of the earth: the sun strikes the earth in a
very concentrated fashion at the equator, whereas at the
poles, the sun's rays are much more spread out.
b) The Seasons: spring, summer, fall, and winter result in
different amounts of heat coming to the earth. This is
caused by the changing position of where the sun is
directly overhead on the earth's surface during the year
and the tilt of the earth's axis.
i.e. Mar. 21 (Vernal Equinox) and Sept. 21 (Autumnal
Equinox): the sun is directly overhead at the equator.
Dec. 21 (Winter Solstice): the sun is directly overhead at
the Tropic of Capricorn (23.5 S).
June 21 (Summer Solstice): the sun is directly overhead
at the Tropic of Cancer (23.5 N). Lower latitudes receive
more sunlight – warm climates with small temperature
ranges
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Higher latitudes = rays of sun are more spread out=
colder climates more temperature extremes = evident in
poles.
http://www-class.unl.edu/geol101i/15a_climate.htm
4) Mountain Barriers: stop the movement of cold air masses. This is
due to the fact that cold air is dense and generally stays near to
the ground.
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Air is forced to rise on the windward side of mountain causing
precipitation
Leeward side the wind falls creating clear, dry conditions=rain
shadow
eg Vancouver is shielded from most Arctic air masses by the
Rockies and Coast Mountains.
Mountains can also result in warm winds descending down slope
eg a chinook: a warm wind. This westerly wind is dry and blows
down the eastern side of the Rockies affecting cities such as
Calgary.
5. Ocean Currents: can either warm or cool a coastal area by approximately
two degrees Celsius.
• Warm and cold ocean currents circulate through out the world’s oceans and
these have a heating/colling effect
• Gulf Stream (warm current) warms areas in Europe (Britain) making the
climate moderate
• Cold Ocean Currents will create dry regions around the globe=Atacama
desert in Chile is a result of cold ocean currents as the bring dry air from
the see over land
Note: Winds produce currents.
6) Nearness to Water or Continentality: the closer a city is to a large body of
water, the more moderate will be its temperatures (i.e. maritime climate),
whereas the further away a city is from the water, the greater the temperature
extremes (i.e. continental climate).
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Locations near water=wetter/moderate
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Interior (Continental) locations are drier and have more temperature extremes
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Ex. Gobi Desert in Mongolia/China (dry interior conditions)
Try to think of differences in climate between a place like Vancouver and Winnipeg…