The Earth's Atmosphere

The atmosphere is the layer of air that surrounds the Earth - It protects us from harmful solar radiation (ex., UV radiation) - It provides living things with the gases they need to live (CO2 for plants, O2 for animals) - It maintains a temperature range on the planet that allows life to exist (without it the earth would be -18ºC)

How thick is the atmosphere? Gravity pulls the gases toward the earth While 99% of the gases in the atmosphere are in the first 30 km above the surface of the earth, the atmosphere is considered to extend more than 10 000 km.

The Composition of the Atmosphere Almost all composed of two gases, Nitrogen (N2) = 78% Oxygen (O2) = 21% Also.. Water vapor = 0-4% Argon = .93% CO2 = .038% Ozone = .000 001% And more...

Atmospheric pressure Because of gravity, most of The molecules of air are close to the earth (99% within 30 km). This means the density and pressure of the atmosphere is greater at lower altitudes. The pressure at the surface Is 14.7 pounds per square inch. (On Mt. Everest the pressure is about 4.5 pounds psi.)

The Layers of the Atmosphere

Troposphere From the surface to 10 - 15 km Most clouds and storms occur in this layer The temperature drops with altitude

Stratosphere 15 – 50 km This layer contains the ozone layer (O3), which absorbs UV radiation, this makes it warmer

Mesosphere 50 – 80 km Very cold (-80⁰C), very few air particles

Thermosphere 80 – 500 km Hottest layer of the atmosphere (up to 2000⁰C), it absorbs most of the sun’s radiation. Because of the rarity of air particles it doesn’t feel hot.

The Exosphere 500 - 10 000 km Basically empty, outer space Satellites orbit earth in this layer.

Atmospheric Circulation Driven by the rotation of the earth and convection. Convection – warm air at the equator rises and travels to the poles. Cold air moves south closer to the surface

The combination of convection and the Earth’s rotation makes the air circulation complex The Coriolis effect is the result Air moves in curved paths

Explaining and predicting the weather The movement of air in the atmosphere has certain trends that we can identify. It’s important to be aware that there is a fair amount of ‘randomness’ or unpredictability in the weather. This is the ‘Butterfly Effect’.

Circulation Cells (acc) Air circulates in loops called cells. The cells are called Hadley, Ferrel, And Polar cells.

The convection currents are divided into cells, but the basic principle of rising warm air and sinking cold air drives the circulation. Prevailing winds are created that move in predictable directions based on the Coriolis effect

To refer to areas on the Earth’s surface, we divide the planet into vertical and horizontal slices called longitude and latitude. Latitude, from 0⁰ to 90⁰ North and South Longitude, from 0⁰ to 180⁰ East and West

Trade winds are easterly(they come from the east) , from the equator to the 30th parallel. Westerlies blow from the west between the 30th and 60th parallel. Polar easterlies blow from the east between the 60th and 90th parallel.

At high altitudes the Jet Streams blow from the west between the cells The Polar is at the 60th parallel, 10 km, <300 km/h The Subtropical - 30th parallel, 12 km, <400 km/h

Air Masses Large volumes of air that are uniform temperature and humidity are called air masses. Quebec receives warm, moist air masses from the South and cold, dry air masses from the North. When two air masses meet, a Front is created. Depending on which air mass is moving, the result can be a cold front or a warm front.

Cold Front A cold air mass pushes the warm air mass up. The warm, moist air condenses. Thunderstorms Are created along the front. Cold fronts are represented with blue lines with arrows.

Warm Front A warm air mass slowly slides over a cold front. Precipitation is spread over a broad area at different altitudes. Represented with a red line with semicircles.

Anticyclones and Depressions The vertical rise and fall of air (as opposed to the horizontal movement of air masses) can cause depressions and anti-cyclones. When warm, moist air rises a depression is created. ‘Depression’ refers to the lower air pressure left behind when the warm air rises. Cold air dropping toward the surface creates a high pressure area. This is called an anti-cyclone.

Depressions can become Hurricanes (aka typhoon, cyclone)

Hurricane Isabella - 2003 – Atlantic Ocean - tropics

Rising warm air creates a low pressure zone. A convection current around the rising air forms. The earth’s rotation creates the spin (Coriolis effect) Wind speed at the can be over 350 km/h. The size of a hurricane can be over 1500 km in diameter.

Anti-cyclone (high pressure zone) This occurs when relatively cold air drops vertically, creating higher air pressure. Skies are sunny and clear.

The Greenhouse Effect Reflected heat radiation off the surface of the Earth heats up gases, which then retransmit the heat, partly back to Earth. Water vapour, CO2, CH4 (methane) and ozone have the greatest contribution to the greenhouse effect, though almost all gases in the atmosphere play a part

The greenhouse effect is what makes the Earth’s climate liveable. But… As more greenhouse gases are released, the concern is that the average temperature will rise too much. Glaciers will melt, etc. CO2 – burning of fossil fuels, clear-cutting forest CH4 – methane produced by cattle and decomposing waste N2O – released from nitrogen rich fertilizers CFC’s – chlorofluorocarbons destroy ozone

It is estimated that the Earth’s average temperature has risen by 0 It is estimated that the Earth’s average temperature has risen by 0.76⁰C in the last 150 years. It is predicted that a rise of 2⁰C would cause widespread environmental consequences.

The Thinning Ozone Layer (acc) In addition to influencing global warming, the ozone layer blocks much of the UV radiation from the sun. This radiation can cause harm to living things through cell damage and genetic damage. For years, CFC’s were used in aerosols and refrigerators. These gases destroy ozone by releasing chlorine that reacts with it.

In 1987, an agreement was reached to stop the production of CFC’s. The hope is that the ozone layer will recover in the next century.

Smog

Smog (acc) Ozone can be harmful to life if it close to the surface. Pollution from human industry and vehicles (nitrogen oxides) reacts with the sun’s rays to form ozone. Mixed with smoke and fog, it is called smog. Smog can cause respiratory (breathing) illnesses.

Energy from the air Wind is a plentiful renewable resource, and we are taking advantage of this more and more by building very large wind turbines. Turbines can be 100 m tall and produce 2 MW of electrical power, enough to supply 2000 homes (based on average household power consumption of 1 kW.)

- Designs are improving - Designs are improving. - Turbines are getting bigger and more powerful. - But the wind isn’t constant. - A combination of energy types will be needed.

That’s it for the atmosphere (take a deep breath). 11/10/2017