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Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Purpose of this document: The notes in this document are meant to supplement your textbook. You are responsible for studying these supplementary notes AND all the ST sections of Chapter 7 in your textbook. The Earth-Moon System: Tides are mainly caused by the gravitational attraction of the Earth and Moon to each other, but also by the gravitational attraction of the Earth and Sun to each other. The gravitational force between the Earth and Moon is greater than the gravitational force between the Earth and Sun. The gravitational force is directly proportional to mass and inversely proportional to distance. Although the sun has more mass than the moon, the distance between the Earth and Sun is much greater than the distance between the Earth and moon. Source: http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide02.html Page 1 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes The Earth-Moon System (continued): The tidal range is the difference between the water levels at low and high tide. Spring tides cause the tidal range to be greater than usual (lower low tides and higher high tides). Neap tides cause the tidal range to be smaller than usual (higher low tides and lower high tides). Please ALSO refer to the document provided in class named "What causes tides?" Please ALSO refer to the video: "Watching the Tides" https://www.youtube.com/watch?v=QcbN9SVkqYU Source: http://oceanservice.noaa.gov/education/tutorial_tides/media/supp_tide01.html Tidal Power Plant Source: http://climatekids.nasa.gov/tidal-energy/ Page 2 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Variation of Atmospheric Pressure and Temperature with Altitude (vertical): http://wps.prenhall.com/wps/media/objects/3083/3157782/blb1801.html The gravitational force of the Earth pulls the air particles in the atmosphere towards the Earth's surface. Consequently, the number of air particles in the atmosphere decreases with increasing altitude (height). This means that the density of the atmosphere also decreases with increasing altitude. Ninety-nine percent of the air molecules in the atmosphere are situated within 30km of the Earth's surface. Atmospheric pressure is the force that air particles exert when they collide with each other and with other objects. When the density of air increases, the number of collisions between air particles increases, therefore atmospheric pressure increases as well. Since air density decreases with increasing altitude, it follows that atmospheric pressure also decreases with increasing altitude. Page 3 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Changes in Atmospheric Pressure and Temperature with Altitude (height): Temperature is a measure of the degree of agitation of the particles of a substance. There are two main factors that are responsible for the variations in temperature within the different layers of the atmosphere: the density of air and the absorption of solar energy. 1) When the density of air increases, the number of collisions between air particles increases, so the degree of agitation of the air particles (temperature) increases. Most of the sun's high energy rays do not reach the troposphere. The temperature in the troposphere decreases with increasing altitude, because the density of air decreases with increasing altitude. 2) The greater the solar energy absorbed by air particles, the greater the degree of agitation of the air particles (temperature). In the thermosphere, the density of air is very low and it decreases with increasing altitude. However, the air particles in the thermosphere absorb very high levels of solar energy. In fact, the higher up within the thermosphere the air particles are, the greater the amount of solar energy they absorb. Consequently, the temperature of the air particles in the thermosphere is very high and it increases with increasing altitude. In the stratosphere, the ozone layer absorbs high energy ultraviolet (UV) rays. In addition, the ozone molecules higher up within the stratosphere absorb the highest energy UV rays. Consequently, the temperature of the air particles in the stratosphere increases with altitude. Changes in Pressure at the Surface of the Earth: In an area of cold air, whether large (e.g. cold air mass) or small (e.g. high pressure centre), molecules have less heat energy, so they move less (lower temperature) and closer to each other. Since cold air has a greater density than warm air, it sinks. Consequently, more air molecules push down on the surface of the Earth, so the pressure at the surface of the Earth increases. In an area of warm air, whether large (e.g. warm air mass) or small (e.g. low pressure centre), molecules have more heat energy, so they move more (higher temperature) and further apart from each other. Since warm air has a lower density than cold air, it rises. Consequently, more air molecules move away from the surface of the Earth, so the pressure at the surface of the Earth decreases. Page 4 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes High pressure centre/ Anticyclone/ Depression Low pressure centre/ Cyclone Source: http://www.slideshare.net/rmarchetto/weather-and-climate-2120822 High and low pressure centres at surface without coriolis force: Surface winds move away from high pressure centres and towards low pressure centres. High and low pressure centres at surface with coriolis force in Northern hemisphere: The Coriolis force causes winds in the Northern hemisphere to deviate to the right from their point of origin. In the Northern hemisphere, wind deviates to the right as it moves away from high pressure centres. Consequently, in the Northern hemisphere, surface winds circulate clockwise around high pressure centres, but counter-clockwise around low pressure centres (the opposite occurs in the Southern hemisphere. Page 5 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Temperature Volume (maximum altitude) Average density Surface Pressure Pressure aloft at same altitude Warm air mass Higher (warm) Cold air mass Lower (cold) Greater (Higher) Low Low Smaller (Lower) High High Higher Lower Changes in Pressure with Latitude (from equator to poles) Aloft (above): H aloft L aloft Page 6 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Changes in Pressure with Latitude (from equator to poles) Aloft (above): Source: http://www.meted.ucar.edu/dynamics/thermal_wind/print.htm The air particles near the equator get a higher concentration of radiant energy from the sun, so they move more (higher temperature) and further apart from each other. Consequently, this warm air takes up a larger volume and has a lower density. The air particles near the poles get a lower concentration of radiant energy from the sun, so they move less (lower temperature) and closer to each other. Consequently, this cold air takes up a smaller volume and has a higher density. The top of the troposphere is closer to the surface of the Earth near the poles than near the Equator, because the warm air near the equator takes up a larger volume than the cold air near the poles. The warm air at the equator rises, whereas the cold air at the poles sinks. Consequently, there are more air particles at the surface of the Earth near the poles than near the equator. The overall number of particles in the atmosphere does not change. This means that there are more air particles aloft (higher up) near the equator than near the poles. The pressure aloft is thus higher near the equator than near the poles. Wind aloft moves from the equator towards the poles, from higher pressure to lower pressure. Page 7 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Winds aloft: Winds aloft move faster than winds at the surface, because the air particles encounter less obstacles (e.g. tree and buildings). In addition, to moving from higher to lower pressure, winds aloft are deflected by the Coriolis force. In the Northern hemisphere, winds are deflected towards the right from their point of origin. In the Southern hemisphere winds are deflected towards the left from their point of origin. Weather associated with high pressure (anti-cyclone) and low pressure (cyclone/depression) centres at the surface: Low pressure centres at the surface are usually associated with clouds and precipitation. Low pressure at the surface is caused by warm air rising. This warm air cools (loses heat) as it rises (since the temperature decreases with increasing altitude), so it leads to condensation, the formation of clouds, and precipitation. High pressure centres at the surface are usually associated with clear and sunny skies. High pressure at the surface is cause by cold air sinking. Source: https://sites.google.com/site/badinoweatherquest/stage-2---forecast-weather/stage-2--forecasting Page 8 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Warm and Cold Fronts: Warm and cold air masses both move towards low pressure centres at the surface, so they eventually collide. Warm front Formation Horizontal Movement Precipitation Clouds Warm air mass displaces cold air mass Cold front Cold air mass displaces warm air mass Slow Light rain (quantity), Over large area, Long duration Fast Heavy rain (quantity), Over small area, Short duration Stratus Cumulus Source: http://slideplayer.com/slide/1447163/ Page 9 of 10 Student Name: ____________________ Chapter 7: The atmosphere and space ST Supplementary Notes Source: http://usatoday30.usatoday.com/weather/wlowpres.htm The Greenhouse Effect and Global Warming: Please refer to the supplemental diagram and notes completed in class. Page 10 of 10