FACTORS INFLUENCING CLIMATE . The factors that influence climate can be identified by using the following anagram: J. BOWLER J. = Jet Stream B = Bodies of water O = Ocean currents W = Winds and air masses L = Latitude E = Elevation R = Relief.
The factors that influence climate can be identified by using the following anagram: J. BOWLER
J. = Jet Stream
B = Bodies of water
O = Ocean currents
W = Winds and air masses
L = Latitude
E = Elevation
R = Relief
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.
The Jet Stream
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.
BODIES OF WATER
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).
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.
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.
The prevailing winds in Ontario are the Westerlies.
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.
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.
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.