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From: Whitney Chenoweth
Date: 11/19/02
Time: 7:39:02 AM
Remote Name: 216.109.17.62
What is the atmosphere?
The atmosphere is the blanket of air that surrounds earth. It reaches over 348 miles from the surface of the Earth, but we are only able to see what occurs close to the ground. With the use of sensitive instruments from space, we are able to get a better view of the functioning of our atmosphere. The atmosphere absorbs the energy from the Sun, recycles water and other chemicals, and works with the electrical and magnetic forces to provide a moderate climate. The atmosphere also protects us from high-energy radiation and the frigid vacuum of space. The atmosphere is primarily composed of Nitrogen, Oxygen, and Argon. Other components that are present are the water, "greenhouse" gases or Ozone and Carbon Dioxide. Four layers of the atmosphere have been identified based on temperature changes, chemical composition, movement, and density. The first layer is the troposphere. This starts at the Earth's surface and extends 5 to 9 miles. This part of the atmosphere is the densest. The temperature drops from about 17 to -52 degrees Celsius the higher up you go. Almost all weather is in this region. The tropopause separates the troposphere from the next layer. The tropopause and the troposphere are known as the lower atmosphere. The next layer is the stratosphere. This layer starts just above the troposphere and extends to 31 miles high. This part of the atmosphere is dry and less dense. The temperature in this region increases gradually to -3 degrees Celsius, due to the absorbing of ultraviolet rays. The ozone layer, which absorbs the ultraviolet radiation, is in this layer. Ninety-nine percent of "air" is located in the troposphere and stratosphere. The stratopause separates the stratosphere from the next layer. The third layer is the mesosphere, which starts just above the stratosphere and extends to 53 miles high. In this layer, the temperatures again fall as low as -93 degrees Celsius as altitude is increased. The mesopause separates the mesophere from the thermosphere. Scientists call the regions of the stratosphere and the mesosphere, along with the stratopause and mesopause, the middle atmosphere. This area has been closely studied on the ATLAS Spacelab mission series. The fourth and final layer is the thermosphere, which starts just above the mesosphere and extends to 372 miles high. The temperatures go up as altitude is increased because of the Sun's energy. Temperatures in this region can go as high as 1,727 degrees Celsius. This layer is known as the upper atmosphere. Beyond these layers is the exosphere. This layer starts at the top of the thermosphere and continues until it merges with space. Hydrogen and Helium are the prime components here and are only present at extremely low densities.
http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html
What is a hurricane?
Hurricanes are a part of a weather system known as “tropical cyclones.” These severe tropical storms develop over the warm tropical and subtropical North Atlantic and North Pacific Oceans and have sustained winds in excess of 64 knots (74 mph). The word hurricane originated from the Caribbean God of evil, Hurricane. The word hurricane is said to mean “big wind.” Hurricanes have been referred to as “The Greatest Storms on Earth.” The title is well earned, as these massive storms can be 600 miles across producing dangerous winds, torrential rains, and flooding. Hurricanes form from clusters of thunderstorms. This pre-existing weather disturbance combined with moisture, warm tropical oceans, and relatively light winds are variables that can cause a hurricane to form. The heat from the warm ocean water is the primary source of energy for hurricanes. High relative humidity reduces in the middle or lower troposphere should also be present. The high humidity reduces the amount of evaporation in clouds and maximizes latent heat released because there is more precipitation. This concentration of latent heat is critical to the driving force of the system. The vertical wind shear in a tropical cyclone’s environment is also a factor in the storm’s development. Wind shear is defined as the amount of change in the wind’s direction or speed with increasing altitude. When the wind shear is weak, the storms that are part of the cyclone grow vertically, and the latent heat from condensation is released into the air directly above the storm, aiding in development. When there is stronger wind shear, this is a sign that the storms will become more slanted and the latent heat is dispersed over a much larger area. The winds of a hurricane are constructed around a central “eye” area, storm clouds wrap in a counter-clockwise motion. From space it has the appearance of a giant pinwheel. This “eye wall” of clouds, wind and rain, is the most destructive part of the storm. In fact, it is the eye wall that creates the eye, since the rapid spinning clouds in the wall reduce the pressure in the eye and suck out any clouds that may be present there. Hurricanes will weaken rapidly when they travel over land or colder ocean waters (locations with sufficient heat and/or moisture). Even so, they can produce high waves and tides up to 25 feet above normal. This is extremely destructive to property. An example of a severe hurricane is Hurricane Andrew. In 1992, this storm caused 50 deaths and over $30 billion dollars in property damage. The town of Homestead, Florida was practically destroyed.
Resources:
http://www.yatcom.com/networl/weather/whatis.html
http://www.firstscience.com/site/srticles/hurricanes/asp
http://www.casde.unl.edu/vn/glossary/earth-h.htm
http://www.flagemergency.com/weather/effects.asp
http://www.nhc.noaa.gov/HAW/index.htm
http://www.sirinet.net/~jgjohnso/weather.html
HBJ School Dictionary, Third Edition. Harcourt Brace Jovanovich, 1990
Background on Hurricane Dennis:
Hurricane Dennis was probably the most unpredictable hurricane of the 1999 Hurricane Season. It stalled, turned, weaved, and wobbled its way along the East Coast of the United States for 10 days. It was probably the wackiest storm since Hurricane Felix in 1995. The category two hurricane’s highest winds were recorded at 105 miles per hour, its highest wind gusts were recorded at over 120 miles per hour, and its lowest barometric pressure recorded at the surface was 28.41 inches/962 mb. Hurricane Dennis was the fourth named storm of the 1999 season and the third hurricane of the 1999 season. It stayed offshore for ten days, bringing winds and waves to the coast of North Carolina and plagued much of the East Coast with heavy surf and riptides. It finally made landfall, over the coast of North Carolina as a tropical storm. http://members.aol.com/windgusts/Dennis.html Dennis formed in the western Atlantic a couple hundred miles east of the Turks and Caicos Islands late on August 23, 1999. The system moved slowly west-northwest for the next five days. The system intensified into a tropical storm on the afternoon of the 24th and a hurricane early on the 26th. Dennis reached peak intensity of 105 mph, which is a category two on the Saffir-Simpson scale, on the afternoon of the 28th and maintained this intensity until early on the 30th and part of the 31st. By this happening, it sustained tropical storm force winds, gusts to hurricane force, large waves and high surf. The hurricane turned northeast away from the coast on the morning of the 30th and began to accelerate later that day while moving to the east-northeast. Dennis stalled about 150 miles east of Cape Hatteras on the morning of the 31st and then began to drift westward and weaken. During the first couple of days of September, Dennis continued to weaken as was downgraded to a tropical storm as it drifted slowly to the southeast along the lower Outer Banks. The storm turned to the northeast on the 4th and made landfall over the Outer Banks between Cape Lookout and Ocracoke as a tropical storm.
http://nwsilm.wilmington.net/tropics/past_storms/1995_1999/dennis/dennis.html
Sphere to Event Interactions:
A>E: Like thunderstorms, hurricanes take place in the atmosphere, the envelope of air that surrounds the earth and presses on its surface. Hurricanes are formed from simple complexes of thunderstorms. Thunderstorm activity is associated with cumulonimbus clouds that generate heavy rainfall, thunder, lighting, and occasionally tornadoes and hurricanes. However, these thunderstorms can only grow to hurricane strength with cooperation from both the ocean and the atmosphere. First of all, the ocean water itself must be warmer than 26.5 degrees Celsius (80 degrees Fahrenheit). This is why you only see hurricanes in gulf coastal regions between June 1st and November 30th. Hurricanes begin when very warm moist air over the ocean rises rapidly. The heat and moisture from this warm water is ultimately the source of energy for hurricanes. Relative to having warm ocean water, high relative humidity in the lower and middle troposphere are also required for hurricane development. The troposphere is the bottom layer of the atmosphere, which consists of air closet to the surface of the earth. It contains over half of all the air in the atmosphere. Temperatures decrease with an increase in altitude. It is the chief focus of meteorologists, because it is in this layer that essentially all important weather phenomena occur. Relative humidity may be defined as the ratio of the water vapor density to the saturation water vapor density usually expressed in percent. In other words, it indicates how moist the air is. If humidity is high, it reduces the amount of evaporation in clouds and maximizes the latent heat released because there is more precipitation. When moisture in the rising warm air condenses, a large amount of energy in the form of latent is released. This heat increases the force of the rising air. Therefore, the latent heat fuels the engine of a hurricane system. Latent heat is heat released or absorbed by a substance, in this case water vapor, as it changes its state. When water vapor condenses in to liquid it releases heat into the surrounding atmosphere. The atmosphere around this condensation then warms. Because warm air rises and cold air sinks, the warmer air takes up more space. The expansion of the air forces more air outside away from the center of the storm and the atmospheric pressure decreases. Atmospheric pressure is the weight of the air above. At sea level the average pressure is slightly more than 1000 millibars. As the surface pressure decreases, a larger pressure gradient is formed, and more air converges, or meets, towards the center of the storm. For example in the Western Hemisphere, from the outer edge to the center, the barometric pressure has, on occasion, dropped 60 milliners from 1000 milliners to 950 milliners. A steep pressure gradient, therefore, generates the rapid, inward spiraling winds of a hurricane. This creates more surface convergence and causes warmer, moist surface air to rise above the surface. Therefore, the low-pressure area acts like a chimney – warm air is drawn in at the bottom, rises in a column, cools, and spreads out. Moist tropical air continues to be drawn into column of rising air, releasing more latent heat and thus sustaining the process. In other words, this causes the storm to grow and form more strength, which in turn forms a hurricane. As the inward rush of warm, moist surface air approaches the heart of the storm, it turns upward and ascends in a rung of cumulonimbus clouds. The greatest speeds and heaviest rainfall occur in the eye wall. Surrounding the eye wall are curved bands of clouds that trail away in a spiral fashion. At the center of the storm is the eye of the hurricane. It is usually a zone about 12.5 miles in diameter. This is where the precipitation ceases and winds decrease. It only gives a brief break from extreme weather in the enormous curving wall clouds that surround it. The air within the eye gradually descends and heats by compression, making it the warmest part of the storm. After forming, a hurricane begins to move in a westerly direction, and then curves toward the north. The Coriolis Effect moves most storm systems. Everything that moves over the surface of the earth is affected by the rotation of the earth on its axis. The rotation causes surface winds in the Northern Hemisphere to turn to the right and those in the Southern Hemisphere to turn to the left, hence the Coriolis Effect. As mentioned earlier, the air in a hurricane travels in a spiral within the storm. In the Northern Hemisphere, the spiraling winds travel counterclockwise – the opposite of the way the hands of a clock move. If you live in the southern U.S. you will notice the clouds will travel in the opposite direction until the eye of the storm has passed, then winds will blow to the east as it is supposed to, according to the Coriolis Effect. Hurricanes can travel 1,000 to 3,000 km and last for 9 to 12 days over the ocean. Eventually it moves over land or colder water. There the source of warm, moist air is cut off, and the hurricane weakens. When it hits land it can do harmful damage to the coastal areas.
Resources: Tarbuck, Edward J. & Lutgens, Fredrick K. “Earth Science.” Prentice Hall, New Jersey, Ninth Edition, 1997, P. 444, 381, 483, 484.
Lauber, Patrica. “Hurricanes: Earth’s Mightiest Storms.” Scholastic Press, NY. 1996. P. 19-21.
Dispezio, Michael, M.A., Lisowski, Marylin, Ph.D, etc. “Science Insights: Exploring Earth and Space.” Addison – Wesley Publishing Company NY. 1996. P. 450, 403.
Ramsey, William L., Phillips, Clifford R. etc. “Modern Earth Science.” Holt, Rinehart, and Winston, Inc. NY. Teachers Edition, 1989. P. 401, 402, 433.
http:ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/mvmt.rxml
http://www.usatoday.com/weather/tg/whurlife/whurlife.htm
A>E Hurricane Formation – Tropical cyclones are born in moist tropical air. About every 4-5 days, a tropical wave of low pressure moves west in the trade winds. Some tropical waves develop into tropical depressions, tropical storms, and hurricanes. In developing tropical cyclones, deep thunderstorms develop. Air pressure drops at the surface, forming low pressure. Low pressure attracts warm moist air near the ocean’s surface. The Coriolis force causes these low-level winds to spiral in a counterclockwise direction around the center of the low in the Northern Hemisphere. Winds swirl clockwise in the Southern Hemisphere. Typically, an “eye” forms when the tropical cyclone reaches hurricane strength, but an eye is not necessary for a tropical cyclone to be a hurricane. Think of a hurricane as a large heat engine. The fuel is moisture from warm ocean water. The moisture is converted to heat in the thunderstorms that form. Spiral rain bands that surround the tropical cyclone's core help feed the circulation more heat energy. As air nears the center, it rises rapidly and condenses into clouds and rain. The condensation releases tremendous amounts of heat into the atmosphere. The result is lower surface pressure and strengthening winds. In this way, the tropical cyclone’s engine refuels itself, concentrating its power in a donut-shaped area, called the eye wall, surrounding the center. The eye wall typically conations the strongest surface winds. Sinking air at the center clears the tropical cyclone of clouds and forms the “eye.” Falling surface pressure can only occur if air mass is removed from the circulation center. This is accomplished by wind flowing out away from the circulation in the upper atmosphere.
http://www.weather.com/enyclopedia/tropical/forecast.html
A>E Hurricane Winds – The winds of a hurricane range from 74 miles per hour (65 knots) in a minimal storm to greater than 155 miles per hour (136 knots) in a catastrophic one. Often accurate readings of high wind gusts during landfall are impossible because the anemometers at reporting wind stations are ripped from their foundations. Wind is responsible for much of structural damage caused by hurricanes. High winds uproot trees and tear down power lines. The maximum winds from fast moving and powerful storms may remain high, even when the storm is well inland. Often this is actual wind speed combined with the speed of the storm. For example, Hurricane Hazel moved through western New York on October 15, 1954, giving Buffalo winds near 100 miles per hour.
http://www.weather.com/encyclopedia/tropical/effect.html
A>E Hurricanes require a special set of conditions. Warm seawater is evaporated and is absorbed by the surrounding air. The warmer the ocean the more water that evaporates. The warm, moist air rises, lowering the atmospheric pressure of the air beneath. In any area of low atmospheric pressure, the column of air that extends from the surface of the water, or land, to the top of the atmospheric is relatively less dense and, therefore, weighs relatively less. Air tends to move from areas of high pressure to areas of low pressure, creating wind. In the Northern Hemisphere, the earth’s rotation causes the wind to swirl into a low-pressure area in a counterclockwise direction. In the Southern Hemisphere, the winds rotate clockwise around a low. This effect of the rotating earth on wind flow called the Coriolis Effect. The Coriolis Effect increases in intensity farther from the equator. To produce a hurricane, a low-pressure area must be more than 5 degrees farther from the equator. Hurricanes seldom occur close to the equator.
http://www.aolsvc.worldbook.aol.com
A>E Hurricanes last an average of 3 to 14 days. A long-lived storm may wander 3,000 to 4,000 miles, typically moving over the sea at speeds of 5 to 20 miles per hour. All hurricanes eventually move toward higher latitudes where there is colder air, less moisture, and greater wind shears. These conditions cause the storm to weaken and die out. The end comes quickly if a hurricane moves over land, because it no longer receives heat energy and mixture from warm tropical water. Heavy rains may continue, however, even after the winds have diminished.
http://www.aolsvc.worldbook.aol.com
A>E The atmosphere affects the intensity of hurricanes. From global climate models, we know that a doubling of the atmospheric carbon dioxide concentration will likely increase sea surface temperature around the globe. This sea surface temperature increase could have an impact on the severity of hurricanes. Using the increased sea surface temperatures, it has been estimated that in the world’s tropical oceans, hurricane strength could increase by thirty to sixty-percent. In this specific region of Florida, it is estimated that hurricane intensity could increase by about forty percent.
http://www.meteor.iastate.edu/gcp/studentpapers/1996/climate/sorensen.html
Event to Sphere Interactions:
E>A: Scientists tracking the global warming gas carbon dioxide (CO2) believe that hurricanes pump more CO2 into the air by rolling oceans. The ocean soaks up about a third of the CO2 coming from fossil fuel burning and forest clearance. But new research shows that hurricanes pump some of the CO2 back into the air and could hold important implications for global warming. Scientists from the Bermuda Biological Station for Research at Berry Beach explain that “hurricanes” are making oceans lose CO2. This enhances the accumulation of the climate warming gas in the atmosphere. In 1995, hurricane Felix passed over the research center giving scientists an ideal opportunity to measure hurricane effects. They form that Felix, plus two other hurricanes (Luis and Marilyn) increased summertime feedback of Co2 to the atmosphere by 55%. At the same time, each hurricane cooled the seawater (near the surface) by 7 degrees Fahrenheit for two to three weeks at a time. Scientists have known that hurricanes cool the sea as they roll the surface and bring cooler water up from below. Seasonally, the ocean soaks up CO2 from the atmosphere in winter and gives back more than it absorbs in the summer. Cooler water has less ability to hold CO2. Splashing waves and breaking bubbles also release CO2. Hurricanes enhance that feedback. Some scientists speculate that warming would bring more hurricanes and increase hurricane intensity. That, in turn, would increase hurricane CO2 feedback. Research shows that it is very important to consider many factors when increase hurricane CO2 feedback and it is very important to consider many factors when trying to determine how one change in the earth’s atmosphere will affect other parts of the environment. Global warming may cause many other side effects, such as changing circulation patents, and various winds. Certain circulation patterns and winds are very important to the development of hurricanes. Changing these patterns may adversely affect hurricane formation.
Resources:
http://www.csmonitor.com/durable/1998/09/03/p4sl.htm
http://www.orgins.org/orgs/reasons/hurricanes.html E>A: A hurricane can be viewed as a giant engine that must be fed a steady stream of fuel to keep it up and running. The fuel for a hurricane is warm, moist air. When a hurricane moves inland, its energy supply is cut off, and the hurricane begins to lose its strength. Land cannot provide the hurricane with the necessary moisture. Contact with land slows the storm’s winds, and the hurricane breaks apart. Even the death of a hurricane can create violent weather. Tornadoes can spin off from a hurricane’s fierce winds. This occurs as air of different densities or air from different directions collides into each other (known as a convergence of air). The two air masses cannot go through each other, so they veer around each other, creating a spinning column of air. When this comes into contact with the earth’s surface, a tornado is born. As the winds in the tornado begin to spin, the warmer or more buoyant air parcel starts rising. This stretches the rotating storm into a skinner band. This has been described as a funnel cloud stretching from the surface of the Earth up into a storm. This funnel cloud behaves like a giant vacuum cleaner, sucking up everything in its path. Although the tornado delivers a punch much less powerful that the total energy contained in the hurricane that gives birth to it, what makes a tornado particularly deadly is that their energy is packed into a very small area. Within that small area, tornadoes kill by sucking up heavy objects as large as cars, trucks, and even railroad cars, throwing them, like heavy weapons, through buildings. The strong winds associated with tornadoes can move materials such as boulders, rocks, sands, and soils, thus contributing to erosion of the land. Tornadoes are most likely to occur in the right-front quadrant of the hurricane. They may also be found embedded in the rain bands (bands of clouds accompanied by heavy rain showers and hurricane-force winds), well away from the center of the hurricane. In general, tornadoes associated with hurricanes are less intense than those that occur in the Great Plains of the U.S. The effects of tornadoes, added to the larger area of hurricane-force winds, can produce substantial damage. Some of the most dangerous hurricanes have made landfall on the U.S. mainland in the states of Texas. Perhaps the hurricane that was responsible for the most recorded tornadoes was Hurricane Beulah in 1967. It spawned at least 115 tornadoes when it made landfall in Brownsville and Corpus Christi, Texas. Other hurricanes that have spawned tornadoes include Hurricane Carla (Central Texas, 1961) that resulted in 8 tornadoes, Hurricane Allen (Brownsville, Texas 1980) that resulted in 29 tornadoes, and Hurricane Alicia (Galveston Island, Texas 1983) that resulted in 23 tornadoes. Hurricane Allen spawned 14 tornadoes as it made landfall between Galveston and Houston; 9 tornadoes touched down the next day between Houston and Tyler. All but two of these tornadoes were small, with winds between 40-72 miles per hour. The strongest tornado occurred near Tyler, with winds in the 113-157 mph range. Studies have shown that more than half of the land falling hurricanes produce at least one tornado. When associated with hurricanes, hail or a lot of lightning does not usually accompany tornadoes. Tornado productions can occur for days after landfall when the tropical cyclone remnants an identifiable low-pressure circulation.
Resources:
Galliano, Dean, Hurricanes, The Rosen Publishing Group, New York, NY 2000
Rooter, Charles, Tornadoes, Creative Education, Mankato, MN, 1998
http://wvec.com/knowledge/tornadoes.htm
http://passporttoknowlegde.com/storm/what/tornad.htm
http://hurricanes.noaa.gov/prepare/tornadoes.html
http://www.marchfield.k12wi.us/science/biology/eproject/erosion.htm
http://www.usatoday.com/weather/hurricane/history/walicia.htm