Sky Watchers Teachers’ Guide: chapter 4
Section 4 Wind
- Prior Knowledge
- Section Summary
- 4.1 Read with Understanding: Wind
- 4.2 Observe
- 4.3 Predict
- 4.4 Reflect
What do you know about wind, the pollution it carries, air masses, and what happens when they meet?
Seagulls flying on wind currents along the shore. When a current of air warms up and rises, new cool air rushes in to fill the space.
Think for a moment about birds. There are birds all over the earth. As you know, many kinds of bird migrate huge distances across the earth, picking up travellers as they go.
Then, even though they move along, there is movement within the flocks. The birds twist and turn, each landing on its own twig or branch. When one takes off, another rises up to fill the space. They fly up, down and side to side. They are fluid.
There are also different kinds of birds, different species, each originating in its own region, each with its own movements.
And so it is with air. Air moves huge distances across the earth. These global winds set up the main direction for air currents in an area--they are prevailing, urging others to come along.
Yet, even though air moves along in a certain direction, there is movement within it. Local air currents twist and turn, each brushing by its own twig or branch. When a current of air warms up and rises, new, cool air rushes in to fill the space. Currents move up, down and side to side. They are fluid.
There are also different kinds of air masses, each originating in its own region, each with its own features. With the right tools, meteorologists can watch these large air masses move around.
Also, air masses essentially run into each other at fronts. Imagine the chaos if two flocks of birds were headed toward each other from different directions. Would one quickly fly up and the other go down? Would they spread apart and swirl around in confusion? Would one retreat? With air, this interaction of air currents causes dramatic and sometimes violent weather.
No, air is not alive, but it certainly affects our lives. Air can be healthy and clean or polluted. Polluted air can travel and cause problems in other regions. The atmosphere is an extremely complex, dynamic three-dimensional system.
Consider this... Although air is not alive, we often attribute it with human or animal qualities, characteristics, or motives. Collect some examples of this from books and poems or come up with some on your own.
Who Has Seen the Wind?
By Christina Rossetti
Who has seen the wind?
Neither I nor you:
But when the leaves hang trembling,
The wind is passing through.
Who has seen the wind?
Neither you nor I:
But when the trees bow down their heads,
The wind is passing by.
Source: The Golden Book of Poetry (1947)
4.1 Read with Understanding: Wind
Air expands and rises when heated. This happens because air molecules bounce around and move apart as they warm up. Since the air is rising, it doesn’t put as much pressure on the earth’s surface, so there is a low pressure area underneath the warm, rising air. As soon as the warm air begins to rise, cooler air flows in to replace it. This flowing air is wind.
Cold air sinks naturally because its molecules are close together, making a high pressure area. Air always flows from high pressure areas to low pressure areas. The greater the difference in air pressure between the two areas, the stronger the winds.
Air moves huge distances across the earth because warm air rises at the equator and cool air from the poles rushes in to replace it. Then, the rising warm air fans out towards the north and south poles where it cools, sinks, and moves back toward the equator.
This movement of air from the poles to the equator would go straight up and down if the earth did not rotate. But because the earth spins, the winds swerve. This is called the Coriolis effect. In the Northern Hemisphere, this effect makes the wind swerve to the right, and in the Southern Hemisphere, the wind swerves to the left.
Global winds are also responsible for carrying air pollution around the earth. Air pollution generated in one place is transported long distances by global wind, from hundreds to a few thousand kilometres in a single day. During this travel, pollutants can be deposited on the ground or on buildings, and can undergo chemical changes. These chemical changes can form an entirely different pollutant. For example, volatile organic compounds and nitrogen oxides may react with oxygen and energy from the sun to form ground-level ozone.
Global winds set up the main direction for air currents in an area. They are prevailing winds. In Canada, the prevailing winds blow from west to east and are called Westerlies. However, North America may owe its discovery to a different prevailing wind: Trade Winds. These carried Christopher Columbus across the Atlantic Ocean in 1492.
Even though air moves along in a certain direction, there is movement within it. Local air currents twist and turn. When a current of air warms up and rises, new, cool air rushes in to fill the space. Currents move up, down and side to side. They are fluid.
In Canada, wind speed is given in kilometres per hour (km/h), and it is named for the direction from which it blows. Ask the wind where it is from, and it will tell you. A north wind comes from the north.
Sea breeze creating waves and blowing grass along a Canadian coastline. Winds blowing on shore are called sea breezes or lake breezes.
Land and Sea
The direction and strength of the winds are affected by local differences in air pressure and temperature, as well as lakes, hills and valleys.
The Atlantic and Pacific oceans, as well as large lakes such as the Great Lakes, cause local land breezes and sea (or lake) breezes.
This happens because land heats and cools more quickly than water. On a warm, sunny day the air above the land warms, expands, and rises. Cooler air from a nearby ocean or lake blows in to replace the rising air. The rising air travels out over the water, where it cools and sinks to replace the cooler air blowing on shore. In this cycle, the winds blowing on shore are called sea breezes or lake breezes.
In the evening when the sun has gone down, the cycle reverses itself. Since land also cools more quickly than water, the air over the water is now warmer than the air over the land. The air heated by the water rises and is replaced by cool air from the land. At the same time, the warm air from the water moves over the land, where it cools and sinks. In this cycle, the winds blowing off shore are called land breezes.
A drawing using arrows that depict the movement of air over sea and land that occurs when there is a sea breeze versus a land breeze. Sea breezes and land breezes occur because land heats and cools more quickly than water.
A similar process occurs between hills and valleys, where the valleys are normally cooler than the hills during the day. Cities and natural features of the landscape such as forests also affect winds.
This is particularly important when local winds carry air pollution. For example, several cities, including the Greater Vancouver Region, lie within the Fraser Valley, where sea breezes push air toward mountain walls. In certain temperature conditions, this traps air that is often polluted by automobile exhaust and other sources. This air is trapped at ground level, where people and animals breathe it in.
A map of North America that has blue arrows overlaid to depict the movement of cold air masses from the north, and red arrows to depict the movement of warm air masses from the south. Air masses are pockets of air with similar temperature and humidity.
There are also different kinds of air masses, each originating in its own region, each with its own features. Air masses are pockets of air with similar temperature and humidity. They extend for hundreds of kilometres and are often classified according to the region that produced them.
For example, an air mass may be called an Arctic air mass if it is cold, dry air that was over snow and ice for a few months in the Arctic. A tropical air mass might be one that becomes warm and moist sitting above the Gulf of Mexico or the Caribbean Sea.
These air masses move, picking up or releasing moisture and heat as they go. For example, an air mass travelling from the Arctic may warm and gain moisture if it moves over one of the Great Lakes. Another air mass may dry out as it moves inland from the Pacific Ocean, losing its moisture in the form of rain or snow as it rises and crosses over the Rocky Mountains.
A drawing that depicts the gentle slope of warm air rising during a warm front versus the steep slope of air quickly rising during a cold front. A cold front pushes warm air out. A warm front is the edge of warm air that arrives when cold air retreats.
Air masses essentially run into each other at fronts. A front is the boundary between an air mass that is entering a region and one that is leaving. Usually the two air masses have different origins with very different temperatures and humidities.
Cold air masses influence the weather by moving forward or retreating out of an area. A warm air mass will never push a cold air mass out of a region because cold air is heavier and denser.
Demonstration: A Cold Front has a Steep Slope
- Rest your hands flat on your desks with your palms down.
- Slide your hands forward toward the front edge of the desk, pause, and pull them backward to the original position.
- What happened to your fingers as you pushed your hands forward? Was there a difference when you pulled your hands back?
Your fingers probably buckled when you pushed your hands forward, as advancing air does, and then flattened when they were drawn back. This is similar to retreating air. The slope of a cold front is, on average, four times steeper than the slope of a warm front. When a cold air mass pushes into an area, there is surface friction between the advancing air and the land beneath it. This friction causes the leading edge to buckle.
Fronts May Cause Severe Weather
The interaction of cold and warm air causes dramatic and sometimes violent weather. Cumulonimbus clouds often develop along a cold front where warm, humid air is rapidly forced up. This can result in thunderstorms and even tornadoes.
Tornadoes begin as funnel clouds, violently rotating columns of air extending from the base of a thunderstorm. Some funnel clouds never quite reach the ground, disappearing back into the parent cloud. If a funnel cloud does touch the ground, then it is a tornado.
The bottom end of a tornado can range in width from approximately 2 m to 2 km. For instance, the tornado that ploughed through Edmonton on July 31, 1987 was about 1 km wide.
Tornadoes rarely travel in a straight line. They cut an erratic course, often bouncing from spot to spot. However, they generally move from the southwest to the northeast at a speed between 20 to 80 km/h.
On average, most tornadoes last about 5 to 10 minutes and travel for about 6 km. However, the Edmonton tornado cut a swath through Alberta’s capital nearly 40 km long. The tornado that raced through Grand Valley in southern Ontario, on May 31, 1985, travelled for 110 km before dissipating.
Demonstration: Simulating a Tornado
- two 2 L clear plastic soft drink bottles
- food colouring (optional)
- duct tape
- cloth or paper towels
- Fill one of the bottles with water until it is half full. Add a few drops of food colouring to make the water more visible.
- Cut a 5 cm piece of duct tape and cover the mouth of the bottle containing the water.
- With the pencil, make a hole in the centre of the duct tape. Make sure that the hole is a little bigger than the pencil.
- Take the second bottle and turn it upside down on top of the bottle containing the water, so that the mouths of the bottles line up. With the cloth or paper towel, wipe any moisture from the necks of the two bottles.
- Cut more duct tape and wrap it around the necks of the bottles so they are firmly attached.
- Hold the two bottles by the neck. Invert them so that the bottle containing the water is on top, and immediately start spinning them in circles.
- Put the bottles on the table with the empty one on the bottom.
- Why does this look like a tornado?
- What part of the tornado do you expect to be the most dangerous?
- Why do you think the origin of a tornado is called a funnel cloud?
Tornadoes are fast, violent swirling winds. In this demonstration, the spinning of the bottles and funnel-shaped opening causes the water to take the shape of a tornado. The hole in the bottle allows for the appearance of the tornado’s tail--the most dangerous part of the tornado.
Tropical Storms and Hurricanes
Peak Atlantic hurricane season is between August and October, when the ocean surface is at its warmest. Warm water, rapid cooling, wind, and the Coriolis effect are conditions that combine to form a hurricane.
- Hurricanes form over warm, tropical ocean water where it is at least 26.5°C.
- The atmosphere above the ocean must cool off rapidly with height, so that rising warm air will continue to rise through the cooler layers, allowing the disturbance to grow.
- Winds at all levels of the atmosphere from the ocean right up to 9000 m must be blowing in the same direction, and about the same speed.
- This is what makes the winds spiral. A hurricane seldom forms any closer than 500 km to the equator because of this effect. Refer to the section on Global Winds on page 4-4 to learn more about the coriolis effect.
Hurricanes Develop in Three Stages
A large area of thunderstorms persists for more than one day, and the circulation of air is organized enough to produce sustained winds of between 37 and 62 km/h.
The low pressure centre deepens, with strong thunderstorms and a well defined circulation pattern produces sustained winds reaching 63 km/h or more. Tropical storms are identified by giving them a name to reduce confusion when more than one storm is active.
Circulation intensifies and wind speeds increase to 119 km/h or more. At this stage, an “eye” or calm area forms in the innermost part of the storm. Spiral bands of torrential rain rotate around the “eye” of the hurricane.
Century farmhouse obscured by blowing snow. Canadian literature abounds with true stories of pioneers, farmers, ranchers and explorers who froze to death only metres away from shelters they could not see.
Blizzards combine high winds, bitter cold and blowing snow. They are dangerous on several counts. First, the snow is often powdery and fine enough for you to breathe into your lungs. Second, the combination of bitter cold and high winds can cause frostbite within seconds. Third, the blowing snow and high winds often reduce visibility to almost zero.
Canadian literature abounds with true stories of pioneers, farmers, ranchers and explorers who froze to death only metres away from the shelter they could not see. In Canada, blizzards are most common in the southern Prairies, the Maritimes and the eastern Arctic.
With the right tools, meteorologists can watch air masses move around and measure the speed and direction of local winds. Air pressure measurements help when predicting wind, since air always blows from areas of high air pressure to low air pressure.
Measuring Air Pressure
The barometer measures air pressure, or the weight of a column of air above a given spot. Before you use a barometer for the first time, set it to the mean sea level (MSL) pressure for your area. You only have to do this once.
Environment Canada gives air pressure readings in kilopascals. Most barometers, however, measure the air pressure in inches and millibars. To convert kilopascals to millibars, multiply the number in kilopascals by 10. To convert kilopascals to inches, divide the number in kilopascals by 3.386.
Close-up of a barometer. If the gold needle is no longer lined up with the black needle, you know that the air pressure has risen or fallen since you last set it.
As soon as you have the mean sea level reading in the correct units for your barometer, immediately set the barometer. Turn it over and adjust the small set screw until the black needle at the front is over the current air pressure. The black needle will move whenever the air pressure changes.
Now turn the gold knob on the front of the barometer until the gold needle is over the black needle. The gold needle acts as a reference and will stay put unless you move it. The difference between the two tells you if the air pressure has risen or fallen since you last set it.
Hang the barometer at eye level on a wall indoors away from direct sunlight, heat or air conditioners. Sunlight and sudden blasts of hot or cold air may affect the readings.
Do not take the barometer off the wall to read it. First, tap it gently. Wait for a minute or so and take the reading. Reset the gold needle by moving it over the black needle.
Generally speaking, when the air pressure rises, it means fair weather is approaching, and when the air pressure falls, it means unsettled weather is approaching. Focus on the numeric readings for the day and the trends that you see over time.
Building a Weather Instrument: Barometer
- empty glass container or soup can
- elastic band
- adhesive tape
- large balloon
- drinking straw
- index card about 8 cm by 13 cm
- Cut a piece out of the balloon large enough to cover the top of the glass jar or soup can.
- Stretch that piece of the balloon tightly over the top of the jar or can and secure it tightly in place with the elastic band.
- Cut the straw so that it is about 10 cm long and trim one end to a point.
- With the sharpened end pointing out, lay the straw on the balloon with the flat end at about the centre of the balloon.
- Glue the straw in place.
- Draw reference marks on one of the long edges of the card at roughly 5 mm intervals. Tape the opposite (unmarked) side of the card to the jar, with the narrow end of the rectangular card extending above the jar top and the marked edge just behind the straw. The marked edge should stick out so that the sharpened end of the straw points to the reference marks.
- Chart the position of the straw against the reference marks on the card each day. This does not give you a numeric reading, but it tells you whether the air pressure is rising or falling. The pressure trend is an important tool in forecasting.
Why it Works
The stretched piece of the balloon acts as a membrane. When the air pressure outside the jar rises, it pushes down on the balloon, forcing it slightly into the jar. This, in turn, causes the end of the straw to rise. Similarly, when the air pressure outside falls, the air pressure in the jar is greater than the air pressure around it, forcing the balloon to bulge slightly. This causes the end of the straw to drop.
Keep your barometer away from sources of heat such as radiators and sunny window ledges. If it is close to a source of heat, then your barometer will act more as a thermometer, with the air inside expanding and contracting to reflect changes in temperature, not pressure.
Wind vane on the top of a metal roof. Wind direction can be determined using a wind streamer or a compass.
Measuring Wind Direction
Wind direction indicates the origin of the wind. For example, a north wind blows in from the north. Wind direction can be determined using a wind streamer or a compass.
Use a compass to find north. Then, select a landmark such as a hill, building or lake to identify one of the four points on the compass--north, south, east or west. This is your point of reference. To figure out wind direction, compare the movement of the flags or tree branches with your point of reference.
Find an area outside, such as a hill or a playing field, where there are no buildings or trees to interfere with the wind. Attach four streamers to the north, south, east and west positions on a paper plate. Mark the positions. Hold the plate in front of you so that it is parallel with the ground. Turn the plate so that the north on your wind streamer is facing north. You can find north the first time using a compass.
Watch to see which direction the wind blows the streamers. If the streamers are blowing toward the south, then the wind is coming from the north. It is a north wind.
Measuring Wind Speed
On days when winds are light, you may want to use the Beaufort Scale to estimate wind speed. British Rear Admiral Sir Francis Beaufort invented this scale in 1805 as a way of estimating the speed of winds at sea. The scale was later modified so that it could be used on land.
|Smoke rises straight up||Calm||Less than 1||0|
|Smoke drifts, but weather vanes do not turn||Light air||1 to 5||1|
|Leaves rustle, weather vanes move, you feel a light breeze||Light breeze||6 to 11||2|
|Wind extends a little flag, keeps leaves and small twigs in motion||Gentle breeze||12 to 19||3|
|Wind raises dust, loose paper and small branches kept in motion||Moderate breeze||20 to 28||4|
|Wind sways small trees and small waves form on ponds||Fresh breeze||29 to 38||5|
|Large branches of trees move, telephone wires whistle and it is hard to use an umbrella||Strong breeze||39 to 49||6|
|Trees bend and walking against the wind is hard||Near gale||50 to 61||7|
|Twigs break off trees||Gale||62 to 74||8|
|Houses and roofs are damaged||Strong gale||75 to 88||9|
|Trees are uprooted||Storm||89 to 102||10|
|Damage is widespread||Violent storm||103 to 117||11|
|Tremendous damage and loss of life||Hurricane||Above 117||12|
A wind gauge, or anemometer, measures the speed of the wind. ECCC records wind speed in kilometers per hour (km/h).
To use a wind gauge, stand in an open spot away from any buildings, hills, walls or trees that may block the wind or change its direction and speed. Find out the general direction of the wind by looking at tree branches or flags. Hold the wind gauge up into the wind so that the dial is facing you. Watch the speed on the dial. Slowly turn the gauge a little to the left and then to the right, watching to see where the wind speed is the greatest. Make a note of that measurement.
Lone tree bent over and blowing in the wind. Find out the general direction of the wind by looking at tree branches or flags.
Building a Weather Instrument: Anemometer
- heavy needle, sticky putty, or hot glue
- ping pong ball
- Cut a piece of thread about 20 cm long.
- Thread the needle and tie a large knot in the end of the thread. Then, stick the needle into one side of the ping pong ball and pull it out the opposite side. Alternatively, use sticky putty or hot glue to attach the thread to the ping pong ball.
- Tie or tape the thread to the centre of the straight base of the protractor so that the ball hangs below the part of the protractor marked with angles. If the protractor is held level, where there is no wind, then the ball will hold the thread over the 90° mark.
- Take the protractor outside. Hold it level and parallel to the wind. The wind will blow the ball. When it does, note the position of the thread on the protractor.
- Record the angle and use the chart to convert the angle to a wind speed.
|Angle of Thread on Protractor||Kilometres per hour|
Long grass blowing in the wind. Wind is included in a forecast when it is expected to be at least 20 km/h.
Wind is reported in a number of ways because there are a lot of different weather conditions that are exacerbated by wind. Wind can make a cold day dangerously cold. It can blow snow or dust, reducing visibility. Tornadoes and hurricanes can bring winds that devastate whole communities.
Weather Reports: The Wind Chill Index and Extreme Cold Warnings
Wind chill is an expression of the cooling sensation you feel on your skin when wind is combined with low temperatures. Wind chill uses temperature-like units to represent the feeling of cold on your skin. It compares the wind’s effect to the way your skin would feel on a calm day with that temperature. For example, if the outside temperature is -10°C and the wind chill is -20, your face will feel as cold as it would on a calm day when the temperature is -20°C.
Frostbite becomes a risk when wind chill reaches -27. The coldest wind chill in Canada occurred at Kugaaruk in Nunavut. The temperature outside was -51°C and the winds were 56 km/h, producing a wind chill of -78.
The wind chill index can help you plan your outdoor activities and decide what to wear.
Weather Reports: Severe Weather and Wind Warnings
ECCC issues a variety of Severe Weather Warnings specifically related to wind.
- Issued for sustained winds of at least 70 km/h or gusts of at least 90 km/h or higher.
Extreme Cold Warning
- Issued when winds of at least 15 km/h are expected to combine with very cold temperatures and wind chill values to produce hazardous outdoor conditions lasting more than three hours. The criteria for this type of warning vary across the country, ranging from wind chill values of -55 in some Arctic regions to -30 in southwestern Ontario.
- Issued if strong winds, cold temperatures and reduced visibilities from snow or blowing snow are expected to persist for four hours or more (6 more hours in the North).
- Issued when one or more tornadoes or funnel clouds are observed or detected on Doppler radar.
Tropical Storm Warning
- Issued when an approaching tropical cyclone is expected to produce winds of 63 to 118 km/h.
- Issued when an approaching tropical cyclone is expected to produce winds greater than 118 km/h.
Weather Reports: Tornadoes
About 80 tornadoes are reported in Canada each year. Most are too weak to cause serious damage. The strength of a tornado is determined by the damage it causes to buildings and structures, using a scale developed by Dr. Ted Fujita, a pioneer of research in tornadoes. The scale used today in Canada is called the Enhanced Fujita Scale and it ranges from EF0 to EF5. This scale is an updated version of the original Fujita Scale. Meteorologists, architects and engineers determined how strong a wind has to be to inflict damage on a certain type of structure. There has only been one recorded occurrence of an EF5 tornado in Canada on June 22, 2007 in Elie, Manitoba. The damages from this tornado were estimated at 39 million dollars.
|EF0||90-130 km/h||Overturns garden sheds, and breaks large branches|
|EF1||135-175 km/h||Breaks glass in doors and windows, rips off shingles|
|EF2||180-220 km/h||Removes large sections of roof and collapses the walls of barns|
|EF3||225-265 km/h||Upper storeys of brick houses destroyed, outer walls removed from most houses|
|EF4||270-310 km/h||Two-storey brick houses almost destroyed, cars and vans carried long distances|
|EF5||315 km/h or more||Destroys virtually everything in its path|
Weather Reports: Hurricanes
Hurricanes are classified by the strength of their winds using the Saffir-Simpson Scale. A Category 1 hurricane has the lowest wind speeds and a Category 5 the highest. No Category 3, 4 or 5 hurricane has made landfall in Canada in over a century.
|Category||Wind Speed (km/h)|
Tropical storms or hurricanes that have severe impacts, either on lives or on the economy, are usually remembered many years after the devastation. These storms become part of weather history. Many feel that, in these cases, reusing the name of such a devastating storm in the future would lack compassion and sensitivity. On April 29, 2004, the World Meteorological Organization granted Canada’s request to retire the name Juan, a Category 2 hurricane which was the most powerful storm to hit Nova Scotia and Prince Edward Island in over a century. This was the first time that Canada had requested the retirement of a storm name.
More information about Canadian hurricanes is available from Environment and Climate Change Canada’s Canadian Hurricane Centre website.
What Does Wind Mean to Me?
If You Are Camping
Pay attention to the forecast when you plan a camping trip, and be prepared for unexpected weather. Pick out a safe refuge near your campsite in case you need shelter from severe weather. Shelter might include a comfort station, shower facility or a low spot in a thick stand of trees.
Cold Weather Winds
Frostbite and hypothermia (low body temperature) occur when more heat is lost than your body can generate. Although this happens more rapidly on a windy winter day, don’t be fooled--you need to guard against frostbite on any cold winter day.
Cold Weather Safety Tips for Kids
- Limit your time outdoors when the temperature is extremely cold.
- Dress appropriately and cover your head, ears and face.
- Use the “buddy” system. You and a friend can check exposed skin on each other’s face for tell--tale white patches where skin is frozen. If you spot frostbite, go indoors immediately for help.
- Keep active. Physical activity generates more body heat.
- Stay dry. Wet clothing speeds up the loss of body heat. If your mitts or boots are wet, go indoors to change them.
Warm Weather Winds
Tornado Safety Tips For Kids
Tornadoes most often occur in the afternoon or early evening from May to September. Play it safe if you see a funnel cloud, or if you hear that a tornado warning has been issued for your area.
- When a tornado threatens take shelter immediately--preferably in the lower level of a sturdy building.
- Stay away from windows and doors--flying glass and debris poses the greatest danger.
- In a house, go to the basement or take shelter in a small room on the ground floor such as a bathroom or closet. If that is not possible then shelter under a sturdy desk or table.
The hazards commonly associated with hurricanes include high winds, storm surges and flooding from intense rainfalls. A storm surge is a swelling of water driven by the strong winds and low pressure of the hurricane. Storm surges can move very far inland and cause extensive damage to buildings, vehicles and people. Storm surges are frequently one of the most overlooked and misunderstood hazards of a hurricane. This surge of water can combine with the normal tide and increases the average water level by 5 m or more.
Hurricane Safety Tips for Children
- During hurricane season, pay attention to weather forecasts and warnings.
- If you live on the coast or in a low-lying area near the coast, move inland and to higher ground. The high winds create huge waves at sea which can be very damaging when combined with a storm surge
- Do not go down to the water to watch the storm. Most fatalities during hurricanes occur as a result of being caught in large waves, storm surges or flood waters.
Wind Carries Air Pollution
New Brunswick, Nova Scotia and Prince Edward Island receive air pollution from the Lower Great Lakes Region, southern Quebec and the eastern seaboard of the United States. Cross-border pollution, due to long-range transport, is the major contributor to this region’s smog problem.
Windsor-Quebec City Corridor
This heavily populated corridor covers a strip about 100 km wide along the Canadian border, extending from Windsor through Toronto and Montreal to Quebec City. This area experiences high levels of ground-level ozone more often and for longer periods than any other part of the country. While much of the smog here is generated locally, air pollution transported from the United States contributes significantly to ground-level ozone in the region.
Rays of sun and wisps of cloud above an Atlantic Canadian lighthouse. Most of the smog in the Maritime Provinces forms elsewhere.
Lower Fraser Valley
This valley, which includes the City of Vancouver, is bordered by the Coastal Mountains to the north and the Cascade Mountains to the southeast. These unique geographical features, along with the sea-to-shore breezes off the Strait of Georgia, restrict air-flow patterns and contribute to the area’s ground-level ozone problem. Here, the majority of the smog is generated locally. Motor vehicles in the Vancouver area are one of the major sources of smog in this region.
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