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The Atmosphere – extends more than 10 000 km above the Earth’s surface The Atmosphere Definition: It is the layer of air surrounding the Earth. • It is made of gases that are essential for life! 1. They block UV and other dangerous rays from the sun. 2. They ensure stable climate on Earth. 3. Include: 02 = For Cellular Respiration CO2 = For Photosynthesis The Atmosphere • • • The air is a mixture of gases, especially nitrogen and oxygen, that makes up the atmosphere! Proportions will changes at high altitude (100 km) Relative humidity: the proportion of air that is made up of water. It is responsible for cloud formation and precipitation. It can reach 4% of the air volume. Pollen! Composition of the atmosphere at low altitude The Atmosphere • Divided in 5 layers. • The higher the altitude, the fewer the air particles in the atmosphere (density decreases). Layer 1 – Troposphere (0 to 15 km) • Include most meteorological phenomena. • Include storms and cloud formation. • The temperature drops of 6.5°C with every 1000m. Layer 2 – Stratosphere (15 to 50 km) • This is where ultraviolet rays are absorbed (ozone layer) • In this layer, temperature increases with altitude. • Air particles are increasingly rare! Layer 3 – Mesosphere (50 to 80 km) • The coldest layer of the atmosphere. • The temperature decreases with altitude. • Almost no air! It can reach -80°C Layer 4 – Thermosphere (80 to 500 km) • It absorbs much of the sun’s rays. • The hottest layer : temperature can reach 1800°C at high elevation. • Celestial bodies such as meteors burn in this layer (ex: shooting stars). • Polar auroras (aurora borealis) form in this layer. Layer 5 – Exosphere (500 km and more) • Almost completely empty. • Almost no air; we can’t gauge its temperature. • This is where we put communications satellites. Atmospheric Pressure • It is the pressure of the air. • Air is a gaseous mixture that contains particles that are constantly colliding with one another. • At sea level, the average atmospheric pressure is 101.3 kilopascals (kPa). • 1 kilopascal = 100-kg mass on an area of one square meter. • CLIP 1.2 Atmospheric Circulation • Definition: the global-scale movement of the layer of air surrounding the Earth. • It rises in the atmosphere above the warm humid regions of the equator and descends over cold and dry regions of the poles. • This phenomenon of CONVECTION helps distribute the solar energy the Earth receives. Coriolis effect – READ PAGE 226 • Due to the rotation of the Earth, currents are deflected to the right in the northern hemisphere and to the left in the southern hemisphere. • This effect is greatest at the poles and least at the Equator because of Earth’s near spherical shape. • http://www.youtube.com/watch?v=mc Ps_OdQOYU Coriolis effect • CLIP! • CLIP 2 ! Air Masses • Definition: large expanse of the atmosphere with relatively uniform temperature and humidity. Cold air = dense SINKS! Warm air = less dense RISES! In Québec • Our climate is subject to the effect of warm air masses from tropical regions and cold air masses from polar regions. Air masses do not mix! Precipitations! Front: the line where the two masses meet! COLD FRONTS • When a mass of cold air meets a mass of warm air! • Warm air rises rapidly, in a sharp ascent and then cools. Condensations = CLOUDS (CUMULUS) CUMULUS • Definition: Puffy clouds which often produce wind and heavy rain. WARM FRONTS • A warm front forms when a mass of warm air moves toward a mass of cold air, rising gently above cold air and creating clouds in stratified layers. NIMBOSTRATUS • Light clouds in stratified layers. Associated with slow to disparse showers. ANTICYCLONE – SYMBOL: H • Definition: Area of atmospheric circulation surrounding a high-pressure centre. The air turns clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. DEPRESSION – SYMBOL: L • Definition: Area of atmospheric circulation surrounding a low-pressure centre. The air turns counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. L In the Northern Hemisphere! Depression Anticyclone Weather! Anticyclone Depression -Clear sky -Clouds -Stable weather -Precipitation -Dry -Sunny -Cold in the winter Cyclones! • Also known as hurricanes or typhoons • Definition: Tropical storm characterized by violent winds revolving around an area of low pressure. • Winds can reach 360 km/h! • Diameter of up to 800 km CLIP 1 CLIP 2 1.3 The Greenhouse Effect • Definition: Natural process that allows the Earth to retain some of the heat it receives from the sun. • Greenhouse gases : water vapour H20, carbon dioxide CO2, methane CH4 and nitrous oxide N2O. 3 Step Explanation ! • 1 – Most of the sun’s rays that reach Earth are absorbed by the ground. • 2 – Once heated, the ground emits INFRARED rays into the atmosphere. Some pass the atmosphere and are lost in space. • 3 – Greenhouse gases trap some of those INFRARED rays and send them back to Earth. How does it work? 1.4 Energy Resources WIND ENERGY • Definition: Energy that can be drawn from the wind. • HUGE: up to 120 m in height PROS • RENEWABLE • No greenhouse gases • No acid rain • No destrcution of ozone layer CONS • Not nice (esthetics) • Unpredictable winds • Energy cannot be stored • Noisy CLIP 1 CLIP 2 One megawatt wind turbine = 150 to 300 households