Earth’s AtmosphereChapter 12 Lesson 1 - Describing Earth’s Atmosphere
Lesson 1 - Describing Earth’s Atmosphere Can you explain …….. • How did Earth’s atmosphere form? • What is Earth’s atmosphere made of? • What are the layers of the atmosphere? • How do air pressure and temperature change as altitude increases?
Importance of Earth’s Atmosphere • The atmosphereis a thin layer that surrounds Earth. It is made of a mixture of gases and particles such as the oxygen, carbon dioxide and water necessary for life on Earth. • The atmosphere provides insulation and helps keep temperatures on Earth within a range in which living organisms can survive. Without the atmosphere, there would be no oceans and no life. The planet would be a cold lifeless rock. • The atmosphere helps protect living organisms from some of the Sun’s harmful rays and meteorites.
Importance of Earth’s Atmosphere The gases in the atmosphere . . . • Keep the Earth warm • Transport energy to different parts of the planet • Provide materials essential for living things Examples: Nitrogen promotes plant growth Oxygen is necessary to animals Plants use carbon dioxide and water to make their food.
Origins of Earth’s Atmosphere • When the Earth formed it was a ball of molten rock which slowly cooled and its outer layer hardened. • Erupting volcanoes emitting hot gases from its interior. These gases surrounded the planet forming its atmosphere. • Ancient Earth’s atmosphere was thought to be water vapor with a little carbon dioxide and nitrogen, but not enough oxygen to support life.
Origins of Earth’s Atmosphere (cont.) • Water vapor is water in gaseous form. • As Earth and its atmosphere cooled, the water vapor condensed into liquid, rain fell, and then evaporated from Earth’s surface repeatedly for thousands of years. • Eventually water began to accumulate on Earth’s surface, forming oceans. • Earth’s first organisms underwent photosynthesis, which changed the atmosphere.
Origins of Earth’s Atmosphere (cont.) • Photosynthesis uses light energy to produce sugar and oxygen from CO2 and water • The organisms removed CO2 from the atmosphere and released oxygen into it. • Eventually the levels of oxygen became great enough to support the development of other organisms.
Composition of the Atmosphere • Today’s atmosphere is mostly made up of invisible gases, including nitrogen, oxygen, and carbon dioxide. • About 78 percent of the atmosphere is nitrogen, and about 21 percent is oxygen. The other 1% is water vapor, Argon, CO2. Ozone (O3) and other gases.
Composition of the Atmosphere(cont.)What else is in the atmosphere besides gases? • The most common liquid particles in the atmosphere are water droplets. • Though microscopic in size, water particles are visible when they form clouds. • Many tiny solid particles, such as pollen, dust, and salt, can enter the atmosphere through natural processes. • volcanic eruptions shoot gases and ash into the atmosphere. • forest fires put carbon dioxide and wood ash into the atmosphere • dust storms add huge amounts of eroded soil particles into the atmosphere. dust sea salt water
Composition of the Atmosphere(cont.) • Other atmospheric liquids include acids that result when volcanoes erupt and fossil fuels are burned. • Acids in the air are formed when sulfur dioxide and nitrous oxide combine with water vapor.
Layers of the Atmosphere The atmosphere has several different layers, each with its own unique properties. The layers, from bottom to top, are: Troposphere Stratosphere Mesosphere Thermosphere Exosphere
Troposphere: (0-6 miles)tropo = “burning” • Layer nearest the Earth • All weather happens here • More than half the air in the total atmosphere is in this layer • Temperature drops as altitude increases (59◦F to -76◦F)
Stratosphere: (6-31 miles)strato = “spreading out” • Temperature goes up with altitude (-76◦F to 32◦F) • Most jets fly here • Protective ozone layer at the top of this layer
Mesosphere (31-56 miles)meso = “middle” • Temperature drops with altitude. (32◦F t o -120◦F) • This is the coldest layer • Meteors burn up in this layer • Radio waves are reflected to Earth in this layer • At this altitude you are above 99.9% of the Earth’s molecules
Thermosphere (56-186 miles) • Temperature goes up with altitude • This is the hottest layer of the atmosphere • Auroras occur in lower portion of this layer known as the ionosphere • The ionosphere’s ions reflect AM radio waves transmitted at ground level. As shown above, AM radio waves can travel long distances at night by bouncing off Earth and the ionosphere.
Exosphere (extends from 186 miles to beyond 300 miles from the Earth’s surface) This is the upper limit of the Thermosphere and our atmosphere. • Temperature goes up with altitude • Pressure and density are so low that individual gas molecules rarely strike one another. • The molecules move at incredibly fast speeds after absorbing the Sun’s radiation and can escape the pull of gravity and travel into space. • Space craft orbit in this layer
Air Pressure and Altitude • Gravity pulls the atmosphere toward Earth, creating air pressure. • At higher altitudes, the air is less dense and air pressure is lower. • At lower altitudes, the air is denser and air pressure is higher.
Temperature and Altitude • Temperature changes in different ways as altitude increases in the different layers of the atmosphere. • In the troposphere, temperature decreases as altitude increases. • In the stratosphere, temperature increases as altitude increases because of the high concentration of ozone. • In the mesosphere, as altitude increases, temperature again decreases. • In the thermosphere and exosphere, temperatures increase as altitude increases.
Lesson 2 - Energy Transfer in the Atmosphere You should be able to explain …. • How does energy transfer from the Sun to Earth and the atmosphere? • How are air circulation patterns within the atmosphere created?
Lesson 2 - Energy Transfer in the Atmosphere Vocabulary Radiation: the transfer of heat energy across distances in the form of electromagnetic waves Conduction: the transfer of heat energy from one substance to another through direct contact without obvious motion. Convection: the transfer of energy from place to place by the motion of heated gas or liquid
Energy from the Sun • Radiation is the transfer of energy by electromagnetic waves. • Ninety-nine percent of the radiation from the Sun consists of visible light, ultraviolet light, and infrared radiation. • The majority of sunlight is visible light that passes through the atmosphere to Earth’s surface, where it is converted to heat. • As energy from the Sun is absorbed by Earth, it is radiated back as infrared radiation. • As Sun’s radiation passes through the atmosphere, some of it is absorbed and some of it is reflected back into space.
Energy from the Sun (cont.) Reflected Solar Energy About 5% of solar energy is reflected by Earth’s surface. About 25% of solar energy is reflected by clouds and Earth’s atmosphere. Absorbed Solar Energy About 20% of solar energy is absorbed by clouds and the atmosphere. About 50% of solar energy is absorbed by Earth’s surface http://education-portal.com/academy/lesson/what-is-solar-radiation-definition-effects.html#lesson
Thermal Energy Transfer Thermal energy always moves from an object with a higher temperature to an object with a lower temperature. • Solar radiation warms Earth's surface. • The ground warms the air that touches it through conduction. • As molecules of air close to Earth’s surface are heated by conduction, they spread apart, becoming less dense. • Less dense air rises, transferring thermal energy to higher altitudes. • Energy moves upward through convection as warm air is pushed upward by cooler, denser air. http://education-portal.com/academy/lesson/mechanisms-of-heat-transfer-conduction-convection-radiation.html#lesson
Lesson 3 –Air Currents Vocabulary • Wind – the movement of air from areas of high pressure to areas of low pressure • trade winds – steady winds that flow from east to west between 30 N latitude and 30 S latitude • Westerlies –steady winds that flow west to east between latitudes 30 N and 60 N, and 30 S and 60 S. • polar easterlies – Cold winds that blow from east to west near the North and South Poles
Vocabulary • jet stream –A narrow band of high winds near the top of the troposphere • sea breeze – wind that blows from the sea to the land due to local temperature and pressure differences. • land breeze – wind that blows from the land to the sea due to local temperature and pressure differenced
Lesson 3 –Air Currents You should be able to explain …. • How does uneven heating of Earth’s surface result in air movement? • How are air currents on Earth affected by Earth’s spin? • What are the main wind belts on Earth?
Global Winds • There are great wind belts that circle the globe, and the energy that causes this massive movement of air originates at the Sun. • Not all areas of Earth receive the same amount of energy from the Sun. Uneven heating causes air to move. • The uneven heating of the Earth’s surface causes air pressure to differ from place to place at the same altitude. • The differences in pressure between areas with low temperatures and high temperatures create wind. • Wind blows from areas of high pressure toward areas of low pressure. area of low pressure area of high pressure
Global Wind Belts Earth’s rotation affects wind direction • Earth's rotation causes long distance winds to curve. • The Earth rotates from west to east. This rotation changes the direction of objects moving over the Earth’s surface. • This is known as the Coriolis effect. • In the Northern Hemisphere, the Coriolis effect defects wind to the right in the direction of motion. • Winds in the Southern Hemisphere are deflected to the left. • http://www.youtube.com/watch?v=mcPs_OdQOYU Plane animation http://www.classzone.com/books/earth_science/terc/content/visualizations/es1904/es1904page01.cfm
Global Wind Belts (cont.) Bands of calm air separate global wind belts. • Global winds travel thousands of miles in steady patterns and are caused by the uneven heating of the Earth’s surface. • Because of the Coriolis effect, winds do not flow directly from the high pressure areas over the poles to the low pressure area at the equator. Instead, each hemisphere has three belts of global winds known as the trade winds, the westerlies, and the polareasterlies.
Low pressure = Ascending or Rising air (weather tends to be rainy) High Pressure = Descending or Sinking air (weather tends to be calm and dry) http://www.youtube.com/watch?v=5QOVwX-6g-Q Global Winds Polar Easterlies – Wind blows from east to west Westerlies – Wind plows from west to east Trade Winds – Wind blows from east to west H 60 Degrees – Low pressure zone 30 Degrees = high pressure zone L H L H The horse latitudesare high-pressure zones located about 30º north and 30º south of the equator. Warm air traveling away from the equator, cools and sinks in these regions. The weather tends to be clear and dry. The Doldrumsare a low-pressure zone near the equator. There, warm air rises to the top of the troposphere, which is the atmosphere's lowest layer. Then the air spreads out toward the poles. The rising, moist air produces clouds and heavy rain. During the hottest months, heavy evaporation from warm ocean water in the region fuels tropical storms. L H Calm regions of high or low pressure
Global Wind Belts (cont.) Calm Regions • The global wind belts in each hemisphere are separated by calm regions of high or low pressure known as the doldrums and the horse latitudes. • In the clam regions winds are light, and they often change direction. • The doldrums are a low-pressure zone near the equator. There, warm air rises to the top of the troposphere, which is the atmosphere's lowest layer. Then the air spreads out toward the poles. The rising, moist air produces clouds and heavy rain. During the hottest months, heavy evaporation from warm ocean water in the region fuels tropical storms. • The horse latitudes are high-pressure zones located about 30º north and 30º south of the equator. Warm air traveling away from the equator, cools and sinks in these regions. The weather tends to be clear and dry.
Global Wind Belts (cont.) Wind Belts • The trade winds blow from the east, moving from the horse latitudes toward the equator. These strong, steady winds die out as they come near the equator. • The westerlies blow from the west, moving from the horse latitudes toward the poles. They bring storms across much of the United States. • The easterlies blow from the east, moving from the polar regions toward the mid–latitudes. Stormy weather often occurs when the cold air of the easterlies meets the warmer air of the Westerlies.
Global Wind Belts (cont.) Effects of Wind on Travel • Sailors used to dread traveling through the doldrums and the horse latitudes. There wasn't enough wind to move their sailing ships. A ship might stall for days or even weeks, wasting precious supplies of food and fresh water. • The trade winds got their name because traders used them to sail from east to west. For centuries, sailors relied on the trade winds to reach North America from Europe. They would return by sailing north to catch the Westerlies and ride them across the Atlantic.
Global Wind Belts (cont.) Jet streams flow near the top of the troposphere. • The uneven heating of Earth’s surface also causes jet streams that travel for thousands of miles in the upper troposphere. These long-distance winds move at great speeds, always from west to east around the globe. • The polar jet stream has a strong influence on weather in North America. It can pull cold air down from Canada into the United States and pull warm air up toward Canada. • Jet streams can affect air-travel times. They flow 6–9 miles above Earth's surface. Airplanes often fly at these altitudes and their travel times can be lengthened or shortened by the strong wind of a jet stream. http://www.youtube.com/watch?v=huweohIh_Bw&feature=player_embedded
Local Winds • Some winds change in regular daily or seasonal patterns. • Winds that change in a regular daily pattern include land and sea breezes. • Winds that change direction with the seasons are called monsoons .
Local Winds (cont.) • Sea breezes and land breezes occur near shorelines. • During the day, land heats up faster than water. The air over the land rises and expands. Denser ocean air moves into the area of low pressure, producing a sea breeze. This pattern is reversed at night, when land cools faster than water. Warm air rises over the ocean, and cooler air flows in, producing a land breeze.
Local Winds (cont.) • Valley breezes and mountain breezes are caused by a similar process. • Mountain slopes heat up and cool faster than the valleys below them. During the day, valley breezes flow up mountains. At night mountain breezes flow down into valleys.
Seasonal Winds • Winds that change direction with the seasons are called monsoons . Monsoons are also caused by the different heating and cooling rates of land and sea. However, monsoons flow longer distances and affect much larger areas. • Winter monsoons occur in regions where the land becomes much cooler than the sea during winter. • During summer this pattern reverses as the land becomes much warmer than the sea. Moist wind flows inland, often bringing heavy rains.
Lesson 4 - Air Quality • How do humans impact air quality? • Why do humans monitor air quality standards?
Vocabulary air pollution - Harmful materials including gases and smoke added to the air that can cause damage to living things and the environment. particulate matter - Tiny particles such as dust, dirt, acid, chemicals or pollen, that is mixed in with air and hazardous to human health fossil fuel - A fuel formed from the remains of prehistoric organisms that is burned for energy. photochemical smog- The combination of smoke and fog; a type of air pollution that occurs when sunlight causes unburnt fuels, fumes, and other gases to react chemically, often seen as a brownish haze. acid precipitation – when sulfur dioxide and nitrogen oxides combine with moisture in the atmosphere and form precipitation that has a pH lower than that of normal rainwater.
Ozone - A gas molecule that consists of three oxygen atoms. greenhouse effect - The process by which certain gases in a planet’s atmosphere absorb and emit infrared radiation, resulting in an increase in temperature greenhouse gas - A gas, such as carbon dioxide or methane, that absorbs and gives off infrared radiation as part of the greenhouse effect.
Causes and Effects of Air Pollution Human activity can cause air pollution, which consists of harmful materials that are added to the air. Pollutants can be gases or particles. Air pollution can cause health problems and other damage
Causes and Effects of Air Pollution (cont.) Human activities produce chlorofluorocarbons(CFC’s) and other chemicals that cause the destruction of ozone in the stratosphere. http://education-portal.com/academy/lesson/the-ozone-layer-importance-and-the-harmful-effects-of-thinning.html#lesson Note: Smaller amounts of these CFC chemicals are now being produced and the ozone layer is healing
Causes and Effects of Air Pollution(cont.) Human activities also increase greenhouse gases Examples of greenhouse gases are carbon dioxide, water vapor, methane, and nitrous oxide. There is 30% more Carbon dioxide in the air now than in the 1700’s. http://education-portal.com/academy/lesson/greenhouse-gases-and-the-enhanced-greenhouse-effect.html#lesson
Causes and Effects of Air Pollution(cont.) Increasing greenhouse gas concentrations may have these climate change effects: • Increase Earth's average temperature (Model’s predict that the average global temperature will rise 2 to 11.5°F by 2100. • Influence the patterns and amounts of precipitation • Reduce ice and snow cover, as well as permafrost • Raise sea level • Increase the acidity of the oceans • These changes will impact our food supply, water resources, infrastructure, ecosystems, and even our own health . http://education-portal.com/academy/lesson/global-warming-atmospheric-causes-and-effect-on-climate.html#lesson
Causes and Effects of Air Pollution (cont.) • Acid precipitation occurs when sulfur dioxide and nitrogen oxides combine with moisture in the atmosphere and create acids that fall as precipitation. • Acid precipitation can be in the form of rain, snow, and fog. • It affects the chemistry of water in lakes and rivers and can harm organisms living in the water.
Causes and Effects of Air Pollution(cont.) • Photochemical smog is air pollution that forms from the interaction between chemicals in the air and sunlight. • Smog forms when nitrogen dioxide, released in gasoline engine exhaust, reacts with sunlight. • A series of chemical reactions produces ozone and other compounds that form smog. • Ground-level ozone is the main component of smog. http://education-portal.com/academy/lesson/what-is-air-pollution-definition-sources-types.html#lesson
Maintaining Healthful Air Quality • Preserving the quality of Earth’s atmosphere requires the cooperation of government officials, scientists, and the public. • The Clean Air Act gives the U.S. government the power to set air quality standards which protect humans, animals, crops, and buildings from the harmful effects of air pollution. • Pollution levels are continuously monitored by hundreds of instruments in all major U.S. cities.
Air Quality Trends • Air quality in U.S. cities has improved over the last several decades. • Ground-level ozone has not decreased much, however, because as the number of cars on the road increases, air quality standards have not kept up with all pollutant levels. • Pollution emissions have declined, even though the population is increasing