FACTORS INFLUENCING CLIMATE
The factors that influence climate can be identified by using
the following anagram:
J. BLOWER
J. = Jet Stream
B = Bodies of water
L = Latitude
O = Ocean currents
W = Winds and air masses
E = Elevation
R = Relief
FACTORS INFLUENCING CLIMATE
JET STREAM
The jet stream is a layer of fast moving (300 – 500 km per hour), high altitude
(20 – 25 km) air flow that forms an ever-changing boundary between cold
air masses from the north and warm air masses from the south.
The polar jet stream steers weather systems and storms across the country.
The position of the jet stream helps determine what the climate is like in a
particular place.
The clash of the different air masses along the polar jet stream front can
produce severe weather, including violent thunderstorms and tornadoes in
many parts of the country.
The jet stream flows from west to east.
FACTORS INFLUENCING CLIMATE
The Jet Stream
FACTORS INFLUENCING CLIMATE
BODIES OF WATER
Large bodies of water heat up and cool down more slowly than land masses.
These large bodies of water have a moderating effect on climate. That means
that places located near large bodies of water experience cooler summers
and warmer winters than places that are located far from large bodies of
water.
Places located along ocean coasts have a maritime climate. This means that
the highest and lowest temperatures don’t range very much and there is
more precipitation.
Places like the Prairies, which are located in the centre of the continent away
from large bodies of water, have a continental climate. This means that the
temperature range they experience is more extreme and climate conditions
are drier.
FACTORS INFLUENCING CLIMATE
BODIES OF WATER
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LATITUDE
Because Canada is a northern country, the latitude plays an important role in
the general climate pattern.
Generally, the further north you are, the colder and drier the climate. This is
caused by two factors – the ways the sun’s rays strike our planet and the
curvature of the earth. The sun’s rays strike the planet in essentially parallel
lines – these rays are more concentrated at the Equator – making that area
very warm. When the same amount of the sun’s rays strikes the earth
further north (in Canada) the heat is spread over a larger area because of
the curvature of the earth.
Because of the northerly location of the country, much of Canada is covered by
the Subarctic and Arctic Climate Regions.
FACTORS INFLUENCING CLIMATE
LATITUDE
FACTORS INFLUENCING CLIMATE
OCEAN CURRENTS
Both warm and cold ocean currents flow along Canada’s coastlines.
Warm ocean currents make places close to the coast warmer than normal for
that latitude, while cold ocean currents make places close to the coast
colder.
The warm Gulf Stream current which flows northward from the Gulf of Mexico
along the Atlantic coast helps bring cool, humid summers and short cool
winters to that region. The warm Gulf Stream also meets the cold Labrador
current in Atlantic Canada which results in more that average precipitation
and fog throughout much of the year.
On Canada’s west coast, the coast of British Columbia is subjected to the warm
North Pacific Drift current. This results in a very maritime climate with lots
of precipitation and moderating temperatures. The Pacific Climate zone is
the only climate zone in Canada where the average monthly temperatures
are ALL above freezing (zero).
FACTORS INFLUENCING CLIMATE
OCEAN CURRENTS
FACTORS INFLUENCING CLIMATE
WINDS AND AIR MASSES
An air mass is a large body of air with the same temperature and moisture
characteristics throughout. The wind speeds and directions are also similar
throughout the air mass. Generally, there are four air masses that influence
the climate and weather in Canada: polar maritime, polar continental,
tropical maritime and tropical continental.
Polar maritime air masses are formed in the north and over the water. They are
generally cold and moist.
Polar continental air masses are formed in the north over the land. They are
cold and dry.
Tropical maritime air masses are formed in the south and over water. They are
generally warm and moist.
Tropical continental air masses are formed in the south and over land. They are
warm and dry.
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AIR MASSES
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Wind is moving air – the winds blow from areas of high pressure to areas of
low pressure – this is called the pressure gradient.
In a low pressure area, the air tends to rise and in a high pressure area the air
descends. When the air pressure is low, the skies are often cloudy and
there is a good chance of precipitation. When the air pressure is high, the
skies are generally clear and the weather is nice.
The winds carry air masses across the country. When a warm air mass and a
cold air mass collide, the warm air rises up over the cold air resulting in
precipitation and storms.
In Canada the prevailing winds (most common winds) are the westerlies –
which blow from west to east.
The direction of the wind patterns is caused by the coriolis force – a force that
deflects moving air to the right from its direction of movement. This force
results in the northeast trade winds, the westerlies and the polar easterlies.
FACTORS INFLUENCING CLIMATE
The prevailing winds in Ontario are the Westerlies.
FACTORS INFLUENCING CLIMATE
ELEVATION
Simply put, the higher the elevation the colder the temperatures. So, as you go
up a mountain – the temperatures decrease. Evidence of this is the fact
that there is often snow on the highest mountain peaks. As you come back
down the mountain – the temperatures increase.
The rate at which the temperatures increase or decrease is called the lapse
rate. The average lapse rate is 1 degree change for every 100 metres of
elevation.
FACTORS INFLUENCING CLIMATE
ELEVATION
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RELIEF
Relief is the change of elevation and it can cause precipitation. As the
mountains force the warm, moist air blowing across them to rise the water
vapour in the air cools and condenses to form clouds. As more water
vapour condenses the water droplets become to too heavy to stay aloft and
fall as rain or snow. Most of the relief rainfall falls on the windward side of
the mountain while the other side (away from the ocean) is the more
protected leeward side of the mountain and has a much drier climate. This
area is sometimes called the rain shadow area.
Precipitation can also occur without mountains. For example, when two air
masses collide one rises above the other and the air cools – water vapour
forms and falls as rain. Sometimes there an be precipitation without having
two air masses or mountains. On warm sunny days, the heat from the sun
can cause warm air to rise in convectional currents – the water vapour
condenses and it rains. The rainfall in Southern Ontario is caused by both
the frontal system and by convection currents – especially in the hot
summer days.
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RELIEF RAINFALL
FACTORS INFLUENCING CLIMATE