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Earth Processes Atmosphere Notes.Pdf Hon Environmental Science THE ATMOSPHERE NOTES Earth is surrounded by a mixture of gases known as the atmosphere. Nitrogen, oxygen, carbon dioxide, and other gases are all parts of this mixture. The Earth’s atmosphere changes constantly as these gases are added and removed. What are two examples of gases being added or removed from the atmosphere? 1. Animals remove oxygen from the atmosphere and add carbon dioxide to the atmosphere through breathing. 2. Plants removed carbon dioxide and add oxygen to the atmosphere through the process of photosynthesis. 3. Volcanic eruptions add gases to the atmosphere. 4. Vehicles add and remove gases from the atmosphere. The primary function of the Earth’s atmosphere is to insulate the surface of the Earth, which slows the rate at which heat is lost and keeps temperatures at which living things can survive. Composition of the Atmosphere Nitrogen makes up 78 % of the Earth’s atmosphere. It enters the atmosphere when volcanoes erupt and when dead plants and animals decay. The second most abundant gas in the atmosphere is oxygen and it enters the atmosphere primarily as an end product of photosynthesis by plants. What other gases in addition to nitrogen and oxygen make up the atmosphere? Argon Carbon dioxide Methane Water vapor In addition to gases, what other substances does the atmosphere contain? Tiny solid particles or atmospheric dust consisting of soil, salt, ash, skin, hair, pollen, bacteria, viruses, bits of clothing, and tiny liquid droplets called aerosols. 1 Air Pressure. Gravity pulls the Earth’s atmosphere toward the surface of the Earth. This causes the atmosphere to be (more/less) dense near the Earth’s surface? In addition, at higher elevations, the air becomes (more/less) dense. WHY do airplanes fly at higher altitudes? What benefits would this have? Planes fly at higher altitudes where the air is less dense. At lower densities, there is less drag and higher fuel efficiency. Layers of the Atmosphere The atmosphere is divided into 4 layers based on temperature changes that occur at different distances above the Earth’s surface. These layers are called the troposphere, stratosphere, mesosphere, and thermosphere. 1. Troposphere : Nearest Earth’s surface Extends to about 18km above the Earth’s surface Almost all weather occurs in this layer Most dense layer of the atmosphere Temperature in this layer decreases as altitude increases 2. Stratosphere : Above the troposphere Extends from 18km 50km Temperatures rise as altitudes increase because of the absorption of UV rays by ozone (O3). Ozone is concentrated in the ozone layer in the stratosphere. Ozone reduces the UV radiation that reaches Earth. 3. Mesosphere : Above the stratosphere Extends from 50km-80km Coldest layer of the atmosphere Measured temps as low as -93⁰C 4. Thermosphere : Layer farthest from the Earth’s surface Extends from 80km- 550km Nitrogen and oxygen absorb solar radiation, so temps as high as 2000⁰C Lower thermosphere absorbs X rays and gamma rays causing atoms to become electrically charged ions. So this layer is called the ionosphere and results in spectacular colors in the night skies near the poles. Ex. The aurora borealis or Northern Lights. 2 INRPRET THIS GRAPH: 1. What happens to temperature as you rise through the Troposphere? Decreases 2. What layer includes the ozone layer? Stratosphere 3. Ozone O3 that reduces the amount of damaging UV radiation that reaches the Earth’s surface. Energy in the Atmosphere The primary source of all energy on Earth comes from the sun. Solar energy reaches the earth as electromagnetic radiation (remember the Electromagnetic Spectrum? radio waves gamma rays including infrared, visible light and UV among others). Only a small amount reaches the Earth’s surface. The rest is either reflected or absorbed. Reflected: refers to energy that changes direction (bouncing back) Absorbed: refers to energy taken up by matter. There are three important mechanisms responsible for transferring heat into the atmosphere: 1. Radiation: the transfer of energy across space and in the atmosphere. Ex. The heat energy you feel when standing in front of a fire. 2. Conduction: the flow of heat from a warmer object to a colder object when the objects are placed in direct physical contact. Ex. 3 3. Convection: the transfer of heat by air currents. Hot air rises and cold air sinks. Ex. If you hold your hand above a hot oven or stove, you will feel the heat because a current of hot air rises up to your hand by convection. The Movement of Energy in the Atmosphere Air that is constantly moving upward, downward, or sideways causes the Earth’s weather. In the troposphere, less dense air warmed by the Earth’s surface, rise into the atmosphere and currents of colder, more dense air sinks. As air current’s rise, they cool, become denser, and sink. So, air currents move back towards the Earth’s surface until they are heated and become less dense. Then the currents begin to rise again. The continual process of warm air rising and cool air sinking moves air in a circular motion, called a convection current. The Greenhouse Effect: The process in which gases trap heat near the Earth and without which the Earth would be too cold for life to exist. How does this occur? Sunlight penetrates Earth’s atmosphere and heats the surface of the Earth. The Earth’s surface radiates heat back to the atmosphere, where some of it escapes into space. The remainder of the heat is absorbed by greenhouse gases, that warm the air and is radiated back towards the Earth’s surface. 4 Global Climate Regulation Air currents move energy around and regulate global climate Coriolis Effect: The Coriolis Effect is the apparent deflection of things (such as airplanes or for our purposes, ocean currents) moving in a straight path relative to the earth's surface caused by the Earth’s rotation. Its strength is proportional to the speed of the earth's rotation at different latitudes but it has an impact on moving objects across the globe. As the earth spins in a counter- clockwise direction on its axis anything flying or flowing over a long distance above its surface is deflected. This occurs because as something moves freely above the earth's surface, the earth is moving east under the object at a faster speed. In terms of affecting the wind, as air rises off of the earth's surface, its speed over the surface increases because there’s less drag as the air no longer has to move across the earth's many types of landforms. Because the Coriolis Effect increases with an item’s increasing speed, it significantly deflects air flows and as a result the wind. In the Northern Hemisphere these winds spiral to the right and in the Southern Hemisphere they spiral to the left. This usually creates the westerly winds moving from the subtropical areas to the poles. Because currents are driven by the movement of wind across the water of the ocean, the Coriolis Effect also affects the movement of the ocean’s currents. Many of the ocean's largest currents circulate around warm, high pressure areas called gyres. Though the circulation is not as significant as that in the air, the deflection caused by the Coriolis Effect is what creates the spiraling pattern in these gyres. Global wind patterns: Winds in the northern hemisphere always flow to the right Winds in the southern hemisphere always flow to the left The picture SEEMS to contradict these statements. Let’s take a closer look… 5 One more look at convection currents Convection currents form when less dense air warmed by the Earth’s surface, rise into the atmosphere and currents of colder, more dense air sinks. As air current’s rise, they cool, become denser, and sink. So, air currents move back towards the Earth’s surface until they are heated and become less dense. Then the currents begin to rise again. The continual process of warm air rising and cool air sinking moves air in a circular motion. 6 .
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