The Atmosphere And SpaceChapter 7

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Atmosphere

•The layer of gases surrounding the Earth.•Acts as a screen, blocking out ultraviolet rays from the sun.•It ensures a relatively stable climate on Earth by retaining heat.•It contains oxygen gas (O2) needed for cellular respiration and carbon dioxide (CO2), necessary for photosynthesis.•It is 10 000 kilometres thick.

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Composition of the atmosphere

The majority of the atmosphere is made up of gases, mostly oxygen (O2) (21%) and nitrogen (N2)(78%), and is what we refer to as air.

Water vapour is another important gas responsible for cloud formation and precipitation. Its measure is referred to relative humidity.

The atmosphere also contains suspended solid and liquid matter originating from the Earth’s surface (dust, pollen, soot, smoke, droplets,,)

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The Earth’s atmosphere consists of 5 layers:

Troposphere:•Located 0-15 km above the surface.•Cloud formations and storms occur here.•The higher the altitude, the lower the temperature. With every 1000 m of altitude, the temperature drops 6.5ºC.

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Stratosphere:•Located 15-50 km above the surface.•Contains the ozone layer (UV protection).•Temperatures rise with altitude because of ozone.•Air particles become increasing rare with increasing altitudes.

Mesosphere:•Located 50-80 km above the surface.•The coldest layer of the atmosphere. The outer layer is -80 ºC.•It contains very few air particles. A human would suffocate within minutes.

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Stratosphere:•Located 80-500 km above the surface.•This layer absorbs most of the sun’s rays.•It is the hottest layer (1800 ºC in outer layer).•Celestial bodies (meteors) burn up quickly leaving a visible trail (shooting stars).•Aurora Borealis (North pole) and Aurora Australis (South pole) occur here. (Northern and southern lights).

Exosphere:•Located 500 km or more above the surface.•Very few air particles present.•Impossible to gauge temperature with a thermometer.•Telecommunication satellites travel in this layer

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Atmospheric Pressure

•Pressure is due to air particles colliding with each other.•At a given temperature, the more collisions that occur, the higher the pressure.•The pressure of our air is called atmospheric pressure.•At sea level, the average atmospheric pressure is 101.3 kPa (kilopascals). One kilopascal equals the pressure of a 100 kg mass on an area of one square metre.

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Factors affecting Atmospheric pressure:

The more particles that are present, the more collisions that occur. This results in higher pressure. The reverse is also true. As you increase in altitude there are less particles of air and therefore, less collisions with air particles. This is why air pressure drops with increasing altitudes.

As air temperature rises, air particles move farther apart instead of increasing the number of collisions. The result is the density of the air drops and becomes “lighter”. Thus, warm air rises as it is displaced by the more dense cool air.

Air molecules move from areas of high pressure to areas of lower pressure. We call this movement wind.

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Atmospheric circulation

•It is the global-scale movement of the layer of air surrounding the Earth.•Warmer humid air at the equator rises and heads toward the poles and then descends over the cold dry regions. At the same time, the cold polar air heads toward the equator. This type of convection distributes solar energy.

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Coriolis Effect

Instead of the air traveling in a straight line to the poles, it is redirected due to the rotation of the Earth.

Since the Earth spins in a West to East direction, winds are redirected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

These movements of air occur in the troposphere and are responsible for the formation of warm front, cold fronts, and subsequent clouds.

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Prevailing Winds

To add to the complexity of the atmospheric circulation, there are winds which form loops called circulation cells.

Hadley cell – Warm air over the equator rises and cools as it travels North to the 30th parallel. It runs into the winds from the Ferrel cell, descends and returns to the equator.

Ferrel cell – Follows a similar pattern from the 30th parallel to the 60th parallel, where it runs into wind from the Polar cell, descends and returns to the 30th parallel.

Polar cell – Air temperature drops to the minimum over the poles, sinks and travels to the 60th parallel where it runs into the Ferrel cell, rises and returns to the pole.

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Near the surface, these circulation cells create a regular wind pattern on a global scale. These are known as the prevailing winds.

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Prevailing winds (continued):•Polar Easterlies from the pole to the 60th.•Westerlies between the 30th and 60th.•Easterly winds between the 30th and the equator.

Our prevailing winds are Westerlies which is why our weather systems move West to East. Also, our local wind can shift directions due to high and low pressure systems.

We also have two high altitude powerful winds, which move from West to East between the circulation cells. The subtropical jet steam is located around the 30th parallel, at a height between 11 and 14 km and a maximum speed of 400 km/hr. The polar jet stream is located around the 60th parallel, travels at a height of 9 -10 km and has a maximum speed of 300 km/hr.

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Air Mass : a large expanse of the atmosphere with relatively uniform temperature and humidity. The climate in Quebec is affected by the warm air masses from tropical regions and cold air masses from tropical regions.

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Front•The line where warm and cold air masses meet. •It is a transition zone where wind direction, temperature and relative humidity change rapidly.•When the two air masses meet, the cold denser air slides under the lighter warmer air.

There are two types:1. Cold fronts2. Warm fronts

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Cold front•It occurs when a mass of cold air moves towards a mass of warm air•The warms air rises, cools and condenses to form cumulus clouds. •This is often accompanied by wind and heavy rain.•It is represented on the weather map by a row of blue triangles.

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Warm front•It occurs when a mass of warm air moves toward a mass of cold air.•The warm air gently rises above the cold air creating stratified layers of light clouds called nimbostratus.•Tend to bring cloudy weather and showers.•Tend to move slower and thus last longer than cold fronts.

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Most air masses move horizontally. Vertical movement also occurs and is responsible for anticylones and depressions.

Anticyclone•When air cools, particles move closer together. The denser sinks toward the ground, compressing the particles beneath it. •This creates an area of high pressure.•It is symbolized by an H on the weather charts.•The air turns clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.•Associated weather is dry and sunny in the summer and cold in the winter.

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Depression•When air warms, it becomes less dense and rises, leaving an empty space beneath it.This creates an area of low pressure.•It is symbolized by an L on the weather charts.•The air turns counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.•Associated weather is cloud formation and precipitation.

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Cyclones (Hurricanes and Typhoons)•When a depression forms over the warm waters of tropical oceans.•Can be 800 km in diameter and wind speeds up to 360 km/hr.•These storms are called cyclones, hurricanes (Atlantic ocean) or typhoons (Pacific Ocean).•These can be powerful enough to cause floods and landslides, uproot trees, shatter windows and tear roofs off buildings.

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Hurricanes gets their names from meteorologists. They proceed in alphabetical order, alternating between girls’ and boys’ first names.

The Saffir-Simpson Hurricane Wind Scale

Category One: Sustained winds 74-95 mph (119-153 km/hr).

Category Two: Sustained winds 96-110 mph (154-177 km/hr).

Category Three: Sustained winds 111-130 mph (178-209 km/hr).

Category Four: Sustained winds 131-155 mph (210-249 km/hr).

Category Five: Sustained winds greater than 155 mph (249 km/hr).

Hurricanes are categorized by their sustained wind speeds:

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2009AnaBillClaudetteDannyErikaFredGraceHenriIdaJoaquinKateLarryMindyNicholasOdettePeterRoseSamTeresaVictorWanda

2010AlexBonnieColinDanielleEarlFionaGastonHermineIgorJuliaKarlLisaMatthewNicoleOttoPaulaRichardSharyTomasVirginieWalter

Future Hurricane Names

Hurricane season: June 1 – November 30

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Greenhouse Effect

1. Most of the sun’s rays that reach the Earth’s surface are absorbed by the ground.

2. Once heated, the ground emits infrared rays into the atmosphere.

3. Some rays pass through the atmosphere and continue into space. Others are trapped by “greenhouse gases” and sent back to Earth, further heating its surface.

•Greenhouse gases consist of Water vapour (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).•Without the GREENHOUSE EFFECT the average temperature on Earth would be -18 ºC. (compare to 14 ºC)

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Intensification of the greenhouse effect

•For thousands of years, the concentrations of greenhouse gases remained relatively constant.•CO2 was produced by forest fires, volcanic eruption and cellular respiration. This was offset by photosynthesis and absorption by the ocean.•Humans have disrupted this balance by burning oil, coal and natural gas and the clearing of land for farming.•CH4 has increased from activies such as digestion in farm animals, manure storage and management, farming in paddy fields, decomposing household waste and distribution of natural gas. In equal concentrations, it has 21 times the greenhouse effect of CO2.•N2O is caused by nitrogen rich fertilizers and some chemical processes.

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Climate change•The abnormal modification of climatic conditions on Earth, caused by human activity.•According to scientists, the average temperature on Earth rose by 0.76 ºC between 1850 and 2005.•Scientists believe an increase of 2 ºC is the critical point where climate disruption is inevitable.•These changes include an increase in droughts, heat waves, floods and a rise in sea levels.

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Contamination Of The Atmosphere

•Aside from the greenhouse gases there are other contaminants that have an effect:

•Sulfur dioxide (SO2) and nitrogen oxides (NOx) cause acid rain and smog.•Metals such as mercury (Hg), arsenic (As) and lead (Pb), produced from oil and coal combustion, waste incineration and glass making. These metals are toxic to human health because they accumulate in living things.•Chlorofluorocarbons (CFCs) are chemical compounds that destroy the ozone layer.•Dust and airborne particles from factory chimneys and automobile exhaust pipes.

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The Thinning Of The Ozone Layer

•The ozone layer is a part of the atmosphere with a high concentration of ozone molecules, approximate altitude of 20 to 30 km.•Ozone (O3) absorb some of the ultraviolet rays from the sun.•CFC was used in refrigeration systems and aerosol cans.•CFCs absorb UV rays and release a chlorine atom. The chlorine atom reacts with ozone, destroying it.•In 1987, 190 countries signs the Montreal Protocol to eliminate CFC use by 2010.

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Smog

•It is a thick layer of fog, smoke and atmospheric pollutants like NO2, SO2and O3.•O3 is created in the troposphere when the sun’s rays hit NOx.•This thick fog of pollution hangs over urban centres when a high-pressure system prevents it from rising into the atmosphere.•Can cause serious respiratory problems.

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Energy Resources

Alternatives to fossil fuels, hydro and nuclear power:1. Wind energy2. Solar energy 3. Tidal energy

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Wind energy

It is Renewable resource because it regenerates naturally and in sufficient quantities, even as it is used.

Old idea: once used to grind grain.

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New application:

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Advantages

•A one megawatt (1 MW) turbine can produce enough electricity to supply 150 – 300 households.•Wind is a renewable resource.•It does not produce any greenhouse gases.

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Disadvantages

•The towers ruin the beauty of the landscape.•It is impossible to predict when or how fast the wind will blow.•Wind energy cannot be stored. It is usually used in combination with another power generating station like a hydro-electric dam.

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Solar RadiationThe Sun•It is a star composed of 75% hydrogen and 25% helium.•At it’s core, its temperature is 15 million degrees Celcius.•It is 150 million km from the Earth.•Its energy takes 8 minutes to travel to the Earth.•High temperatures cause nuclear reactions in the core to produce its energy.•http://www.energyquest.ca.gov/story/chapter13.html

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Solar energy

It travels to the Earth via electromagnetic waves.Although solar radiation contains all of the waves in the electromagnetic spectrum, only light, infrared rays (heat) and some ultraviolet rays hit the Earth.

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Electromagnetic Spectrum

Due to the curvature of the Earth, tropical regions receive more solar energy then the polar regions.

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Passive heating systemsDesigning houses with south-facing windows to allow the Sun to heat the air. They also use materials like cement that absorb energy and release it later.

Photovoltaic cellsWhen these cells (made of silicon) are hit by light, it causes electrons to flow (electricity). These cells can be found on houses, appliances (lights, calculators) and satelites

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Technologies

Solar collectorsThese are large glass panels that capture the sun’s rays and heat copper pipes filled with water.The heat stored in the pipes is used to heat air and water. (ex. Home heating , pools..)

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Advantages•Renewable energy source.•No greenhouse gases produced.•Energy option for areas with no electrical distribution network, like the Far North or outer space.

Disadvantages•Very expensive•Amount of energy depends on the position of the sun and the amount of cloud cover.

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The Earth-Moon System

Moon•It is thought to have formed when the Earth was hit by an enormous meteor. The pieces of the Earth reunited in space to form the moon.•Its diameter is 3476 km (1/4 the Earth’s diameter).•It takes 27.3 days to rotate around the Earth.•It also spins on its axis. It is why we always see the same side of the moon.

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Tides

•The moon stays in orbit due to the gravitational force between itself and the Earth. Since water is fluid, it bulges in the direction of the moon (high tide).•Also, on the opposite side of the Earth, the water is less attracted to the moon than the Earth. The Earth is therefore drawn closer to the moon than the water. The result is a bulge on the other side of the Earth (high tide).•The other parts of the Earth have resulting low water levels (low tide).•Two high tides and two low tides occur every day.•Tidal range, the difference in water levels at low and high tides, is influenced by slope and shape of coastline, the depth of the water and the distance from the Moon or Sun.

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The Bay of Fundy tides.

low

high

When the Moon and Sun pull on the Earth’s water in then same direction , Spring Tides result. Water levels will be at their highest and lowest.

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Tidal energy

•Tidal power plants harness the energy from this moving water.•The tides come in and fill a huge basin. When the tide retreats, a gate ins opened allowing water to flow through a turbine. This generates electricity.

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Advantages•It uses a renewable source of energy.•It does not produce greenhouse gases.•It is reliable because tides are easily predicted.

Disadvantages•Building the plants are complex and costly.•There are very few sites suitable. (Must have a tidal range of at least 5 metres.)

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Tornadoes http://www.weatherwizkids.com/tornado.htm,http://www.nssl.noaa.gov/edu/safety/tornadoguide.html

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