Download Factors Controlling Climate

Factors controlling climate
Ladislaus Chang’a
Institute of Resource Assessment
Tanzania Meteorological Agency
Education Program on Climate Change and Biodiversity Conservation,
Institute of Resource Assessment, University of Dar es Salaam,
19 July, 2010 - 3rd September 2010
Controls of Climate
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Latitude
Land and Water
Ocean Currents
Prevailing winds and mountain ranges
Local winds
Elevation
Cloud Cover
Latitude
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Latitude is the measure of the distance north
and south of the equator. Latitude is measured
in degrees. Areas close to the equator, or 0
degrees latitude, receive the direct rays of the
sun. These direct rays provide the most radiant
energy. Areas near the equator have a warm
climate. Polar regions have a cold climate.
Elevation
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Elevation, or altitude, is the distance above sea
level. As elevation increases, the air becomes
less dense. This means there are fewer gas
molecules in the air and they are spread far
apart. Less- dense air cannot hold as much
heat as denser air. So as elevation increases,
temperature decreases.
Location
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The surface temperature of water affects the
temperature of the water above it. Warm water
warms the air and cold water tends to cool it. Land
areas near warm water currents have warm
temperatures. The Gulf Stream is an ocean current
that carries warm water along the eastern coast of
the United States. The California Current travels
toward the equator carrying cold water along the
west coast of the United States.
The effects of prevailing wind and
mountain ranges on climate
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The two factors that affect the amount of
precipitation at a particular location are
prevailing winds and mountain ranges.
Prevailing Winds
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A wind that blows more often from one direction
than from any other direction is called a prevailing
wind. Prevailing winds have a great influence on
the climate of regions in their path. Different
prevailing winds carry different amounts of
moisture. The amount of moisture carried by a
prevailing wind affects the amount of precipitation a
region receives. Winds formed by rising warm air
tend to bring precipitation.
Direction of Prevailing Winds
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The direction from which a prevailing wind
blows also affects the amount of moisture it
carries. Some prevailing winds blow from the
water to the land (sea breeze).
Mountain Ranges
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The amount of precipitation at a particular location
is also affected by mountain ranges. A mountain
range acts as a barrier to prevailing winds. The
windward side of a mountain has a wet climate. On
the leeward side, relatively dry air moves down the
side of the mountain and results in very little
precipitation.
Effects of mountains
Local Winds
Generally move short
distances and can blow in
any direction
n Caused by geographic
features that produce
temperature differences
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Sea Breezes
High pressure is created over the
ocean during the day and low
pressure over land due to
uneven heating
n  Air moves from the ocean to the
land creating a sea breeze
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Land Breezes
Low pressure occurs over the
ocean during the night and high
pressure over land due to the
uneven heating of earth
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the land to the ocean creating a
land breeze
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Ocean Currents
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Ocean currents are
organized movements
of ocean water created
by persistent wind
patterns.
Fig. 7.29
Effect of Clouds (Day)
First, assume no
clouds present
Lots of sunlight
reaches surface
Lots of sunlight is
reflected back
into space
Send in the clouds!
Less sunlight reaches
the surface
Result: cooler temperatures
Effect of Clouds: Night
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Clouds reduce flow of infrared radiation to
space
Result: Warmer temperatures
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Diurnal Temperature Range
(DTR)
DTR = Daily Maximum Temperature
minus
Daily Minimum Temperature
Clouds reduce DTR