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From: Cat
Date: 11/23/02
Time: 9:44:50 AM
Remote Name: 80.74.169.140
Hurricanes and Earth Systems Interactions
The Spheres:
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 "greenhouse" gases: water vapor, ozone (oxygen – O3), 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 about 31 miles high. This part of the atmosphere is dry and less dense. The temperature in this region increases gradually to about -3 degrees Celsius, due to the absorption 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 about 53 miles high. In this layer, the temperatures again fall to 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 about 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 in extremely low densities.(http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html)
The biosphere is within the Earth’s thin zone of lower atmosphere, soil, and water in which life is supported. It ranges from about 6 mi. into the atmosphere to the depths of the deepest ocean floor. The biosphere has sustained life for hundreds of millions of years. The biosphere can be subdivided into various regions of growth patterns called biomes. (http://encarta.msn.com/encnet/refpages)
In the hydrosphere, water is a critical element that sustains life and drives a variety of environmental processes acting within the earth system. (http://uwsp.edu/geo/faculty/geog101/modules/hydro.../) The hydrosphere is often called the “water sphere” as it includes all the earth’s water that is found in oceans, streams, lakes, the soil, groundwater, and in the air. The hydrosphere interacts with, and is influenced by, all the other earth’s spheres. Water is held in oceans, lakes, and streams at the surface of the earth. Water is found in vapor, liquid, and solid states in the atmosphere – liquid and solid states are precipitation such as rain and snow. The largest amount of water storage is in the oceans, which contain over 97% of the earth’s water. Most of this water is salt water. The average depth of the oceans is 3,794m (12,447 ft), more than five times the average height of the continents. (Http://encarta.msn.com/encnet/refpages/RefArticle.aspx?=761569459¶=6)
Ice caps, like those found covering Antarctica, and glaciers that occupy high alpine locations comprise a little less than 2% of all water found on Earth.
Water beneath the surface comprises the next largest storage of water. Groundwater and soil water together make up about .5% of all water (by volume). (http://www.uwsp.edu/geo/faculty/ritter/geog101/modules/hydrosphere/hydrosphere.html)
In Latin, hydro means water. Anything that scientists describe, when it comes to water, is a part of the hydrosphere. Water in its purest form is H20 and it is a small molecule that is very busy. (http://www.geography4kids.com/files/water_hydrosphere.html)
The lithosphere contains all of the cold, hard solid land of the planet's crust, the semi-solid material underneath the crust, and the liquid molten rock near the center of the earth. The surface of the lithosphere is very uneven and divided into several layers. The solid, semi-solid and liquid materials of the lithosphere form layers that are physically and chemically different. These layers from the outside to the inside are the crust, mantle, and core.
The rocky material which comprises the crust part of the lithosphere of the earth can be pushed and deformed like putty in response to the warmth of the Earth, such that the rocks actually flow. The flowing lithosphere carries the crust of the earth, including the continents, on its back. The rocky material which comprises the lithosphere of the earth is special, however, because the rocks contain water. These water laden minerals have the ability to slide against each other. The lithosphere is divided up into approximately 14 pieces called tectonic plates. These plates slide over the semi-molten mantle layer below and form the continents and ocean basin. The process of moving plates is known as the Plate Tectonic Theory. Many calculations about the earth are needed to know the thickness of the crust layer of the lithosphere. Some assume that it is 120km, while others think it is closer to 250km. (Microsoft® Encarta® Reference Library 2002. © 1993-2001)
The Event: Hurricanes
Hurricanes are cyclones that develop over the warm tropical oceans and have sustained winds in excess of 64 knots (74 miles/hour). Hurricanes are “organized” storms of very low pressure. Like all areas of low pressure, they eventually move in response to upper level winds. Hurricanes are among the most destructive storms on Earth. They can cause havoc due to their strong winds, rains, tornadoes, the effects of very low air pressure, and resulting floods. (http://www.cotf.edu/ete/modules/sevweath/swintensity.html) Hurricanes are formed when large areas of the ocean become heated, and the air pressure over that area drops. This causes thunderstorms and strong surface winds. Cyclones develop over tropical or sub tropical waters (for example, in the Atlantic off the coast of Africa, or in the Pacific near the equator). As they travel long distances gathering energy from the ocean, they are likely to be classified as strong Tropical Cyclones. When the winds around the cyclone reach speeds greater than 74 mph, the cyclone is called a hurricane in the Atlantic and Northeastern Pacific, or a typhoon in the Pacific. Regardless of the region, there are common elements required for the storms to begin: warm ocean waters (over 79 degrees Fahrenheit), days of warm temperatures and high humidity, and light winds. Although these storms begin over 60% of the world’s tropical latitudes, they do not form in the region between about five degrees north and south of the Equator. This is due to the fact that at those latitudes, the Earth’s spin has little effect on organizing thunderstorm masses into whirling tropical storms. (http://www.usatoday.com/weather/hurricane/whclimo.htm) Once all the prerequisite conditions are in place, moisture from the warm waters evaporate bringing warm moist air high into the atmosphere providing the potential fuel for the hurricane. (http://kids.mtpe.hq.nasa.gov/archive/hurricane/index.html) Once there, winds begin to circle (counterclockwise north of the equator or clockwise south of the equator), gain strength, and move toward the center. The center of the storm, called the eye, is from 10 to 30 miles wide. Within the eye, the winds are calmer, the skies clear, and temperatures warm. It is created as some of the air from the top of the eye-wall moves inward and sinks. (http://kids.mtpe.hq.nasa.gov/archive/hurricane/creation.html; http://www.cotf.edu/ete/modules/sevweath/swwhatare.html) As more moist air is brought up from the warm waters, the storm begins to grow in size and strength perhaps up to 400 miles wide. The most violent activity within the storm takes place in the eye-wall, the area immediately around the eye. At the top of the eye-wall (up to 50,000 feet), the winds are propelled outward increasing the storm’s upward motion bringing more potential fuel for the storm in the form of warm moist air. (http://kids.mtpe.hq.nasa.gov/archive/hurricane/creation.html) Should one of the prerequisites no longer exist (i.e. the storm moves over land or cooler waters) the storm loses its power source and slowly weakens. http://www.cotf.edu/ete/modules/sevweath/swhoware.html) On average, each year, ten cyclones develop over the Atlantic Ocean, Caribbean Sea, or Gulf of Mexico. About six of these will strengthen enough to become hurricanes. (Http://kids.earth.nasa.gov/archive/hurricane/index.html)
Hurricanes are classified into different categories according to the Saffir-Simpson Scale. Developed in the 1970s to characterize the destructive potential of hurricanes, this scale includes maximum sustained wind speed, central pressure, storm-surge height, and coastal destruction potential. Storms are classified into one of five intensity categories from the least at Category 1 (minimal damage, occurring more frequently) to the greatest at Category 5 (catastrophic, likely to occur about once every hundred years). http://www.cotf.edu/ete/modules/sevweath/swintensity.html) These storms are capable of producing dangerous winds, torrential rains and flooding, all of which may result in tremendous property damage and loss of life in coastal populations. One memorable storm was Hurricane Andrew which was responsible for 40 deaths and damages up to $25 billion dollars in Florida and Louisiana. Andrew caused violent winds and storm surges characteristic of a Category 4 hurricane in Dade County. (http://www.msnbc.com/modules/slideshow/hurricane_990913/slideshow.asp) A hurricane requires an excessive amount of energy to swirl the winds around at speeds sometimes in excess 180 mph. This amount of energy is equivalent to frequent atomic explosions. It has been estimated that harnessing just one percent of the energy of a powerful hurricane could provide all the power, fuel, and heating needs of the United States for an entire year. (http://www.cotf.edu/ete/modules/sevweath/swwhatare.html)
Interactions and Causal Chains:
E>A>L>B and E>H>L>B: The barrier islands off the U.S. Atlantic coast are by their very nature dynamic—the one constant being constant change. The area between the barrier islands, called the Outer Banks, and the eastern mainland is a set of habitats called an estuarine system. Here lives a remarkable community of life ranging from the magnificent osprey to microscopic zooplankton. It is a richly diverse community whose variety is dependent on the variables of water level, salinity, and temperature. The geographical location puts this area at the northern extremity of southern biota and at the southern extremity of northern biota. In North Carolina estuaries vary considerably from broad shallow sounds to narrow bodies of water with differing water levels, basin types, tidal patterns, salinity, temperature, and sediment patterns. These characteristics make each estuary unique, and they are home to equally unique communities of plants and animals. Each habitat creates “niches,” roles that each organism plays in maintaining the balance of the natural system. These patterns of life (who eats and produces what) are described as food chains or food webs. Ninety-five percent of the commercial fish species caught in the state depend on the nutrients and shelter of the estuaries during some part of their lives. (http://www.wetmap.org/Cape_Hatteras?Suppliment/ch_background) In these barrier islands powerful storms, like Hurricane Dennis, create the most visible and dramatic land reformation changes simply because they redistribute large quantities of soil in a relatively short period of time. The winds and especially the storm surge of hurricanes push barrier island sands toward the mainland in what is termed overwash. The overwash may bury and smother everything on the landward side of the islands including forests, high and low tidal salt marshes, herbaceous grasslands, woody scrub vegetation, and sea grass beds.
E>H>L>B: As the storm brings in increased wave and current action, salt water is forced into fresh water estuaries and bayous. This sends animals, such as snakes, fleeing from the area which can in turn affect humans as well. (http://hurricanes.noaa.gov/prepare/surge.htm) Due to the winds, rains, and storm surge, inlets—openings between the islands—may be opened or closed, permanently changing the salinity in the brackish water of the sounds, making the water either too salty or not salty enough for those species normally found in that area. This, in turn, can affect the food chains which are dependent on species at the bases of those food chains, or are part of the lower levels of those chains. (http://www.wetmap.org/Cape_Hatteras?Suppliment/ch_background) Examples are water borne organisms and the insect larvae which feed on these organisms.
E>A>H>B: Hurricanes will blow sea water into fresh water, such as lakes and streams, due to the extreme wind speed of the storm causing a disturbance in pH balance of the fresh water. Of course, this would not be beneficial for any living thing that depended on that fresh water and a stable alkalinity/acidity level (pH). (http://kids.earth.nasa.gov/archive/hurricane/index.html) Hurricanes will blow other contaminates, such as raw sewage, paper, anything not contained, into sea water and fresh water streams and lakes or drinking water supplies due to the excess speed and duration of winds. 74 mph or higher winds will send anything anywhere! These contaminates could cause water to be unable to support aquatic life and be unfit for human or other animals’ consumption. (http://kids.earth.nasa.gov/archive/hurricane/index.html ; http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761565992)
E>H>L>B: Torrential rains that frequently accompany hurricanes can cause flooding, increasing sediment flow from rivers feeding the estuary (that can smother aquatic plants and animals). Such rains may also rapidly lower salinity of brackish water on the western side of the sounds stressing aquatic life that is sensitive to salinity levels. Increased organic pollution brought by the flooding can cause bacterial overgrowth that rapidly depletes the oxygen level of the water and produces large fish kills, which in turn add to the organic matter, creating “dead zones” where nothing but bacteria live until the waters can be remixed and cleansed. Disease and starvation may flow up the food chain as animals dependent on other life forms are deprived of their food source.
E>H>B>B: Mosquitoes, on the other hand, may thrive in newly created, stagnant water bodies, acting as vectors to spread disease to man and animals alike. (http://www.nitrate.com/nov99.htm)
E>H>B>L>H>B Torrential rains and flooding can contaminate water supplies for communities when sewage treatment plants are flooded. When this occurred in North Carolina in 1999, after the Tar River overflowed its banks, the water was deemed unusable for drinking or bathing fearing it harbored dangerously high levels of coliform bacteria from fecal sources. (http://earthobservatory.nasa.gov/Study/FloydIntro/) Large amounts of floods and rains from the storm can result in sediment, debris, and pollutants (including sewage, contents of fuel tanks, and carcasses of dead animals) being washed into the coastal waters from the rivers. Rivers can become polluted from the debris felled during the storm. There can be changes in levels of salt and oxygen. In the days following Hurricane Floyd, there were drops in levels of dissolved oxygen in the Pamlico River. This was attributed to outflow from swamps and decomposing organic matter in the flood runoff. Also, there were drops in salinity levels, which had been high due to prevailing drought conditions. These changes were attributed to the massive outflow of the highly polluted freshwater. The dissolved oxygen levels recovered within weeks; however, it took months for the salinity levels to return to normal levels. (http://earthobservatory.nasa.gov/Study/FloydFear/fear.html; http://earthobservatory.nasa.gov/Study/FloydIntro/) Dissolved oxygen is absolutely essential to support respiration of aquatic animals. Various species of plants and animals are sensitive to changing levels of water salinity. Even small changes in the chemistry of the water can affect the food chain and organisms dependent on it.
E>A>H>L>B: Inland forests may be stressed by both the high winds and flooding rains of the hurricane. Many animals are no doubt injured or killed in such storms, or in the aftermath of habitat destruction. (http://lternet.edu/hfr/data/hf002/hf002.html) However, in the long term, hurricanes may bring about greater diversity within the forests by opening the canopy, bringing down old trees which become nurseries for young seedlings, and providing better conditions for more diverse populations of plants and the animals that live on/with them. (http://www.uga.edu/srel/hugo.htm)
E>H>E>A>H>B and E>H>E>A>H>L>B: Hurricanes are an important part of the natural scheme of things because they help thin out species that might otherwise dominate an ecosystem. They also stir up the ocean water and add much needed dissolved oxygen to oceanic "dead zones." They rekindle growth of opportunistic plants and provide critical food for animals. Their beneficial effects start before they ever get close to the shore. Hurricanes vertically mix up the water column which breaks up dead zones of oxygen-poor water. As hurricanes get closer to the shore, this mixing breaks up pockets of fresh water that are infested with bacteria from stream run-off. Along the coast, strong currents created by a hurricane's storm surge flush out sediment, rubble and weeds from coral reefs, and blast away fungal diseases that damage coral. The storms also draw up nutrient-rich water from below, which provides a major food source for sea life. (http://www.explorezone.com/archives/99_09/20_hurricane_benefits.htm) In 1999, Hurricane Floyd caused the mixing of the sediment washed into the coastal waters to be much deeper than normal, re-suspending sediments that had settled on the continental shelf nearly 200 meters below the surface. This was supported by images from remote sensing data such as the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). (http://earthobservatory.nasa.gov/Study/FloydSediment/)
E>H>A>H>L and E>A>H>L: Hurricanes bring with them huge amounts of rain. A big hurricane can dump dozens of inches of rain in just a day of two, much of it inland. That amount of rain can create inland flooding that can totally devastate a large area around the hurricane's center. High sustained winds cause structural damage. These winds can also roll cars, blow over trees, and erode beaches (both by blowing sand and by blowing the waves into the beach). The prevailing winds of a hurricane push a wall of water, called a storm surge, in front of it. This surge of water, topped by wind caused waves, causes considerable (perhaps the greatest) threat to life and property as it sweeps along the coastline. If the storm surge happens to synchronize with a high tide (We would have to insert a new sphere, the “lunasphere,” into the causal chain!), it reaches its greatest height, causing beach erosion and significant coastal flooding. A very strong hurricane over shallow offshore water produces an even higher surge of ocean water as determined by the slope of the continental shelf. (http://www.howstuffworks.com/hurricane5.htm; http://kids.mtpe.hq.nasa.gov/archive/hurricane/damage.html; http://earthobservatory.nasa.gov/Library/Hurricanes/hurricanes_3.html; http://hurricanes.noaa.gov/prepare/surge.htm)
E>H>L>B: Large amounts of rain can occur more than 100 miles inland causing flash floods which wash away roads and bridges. These rains and flash floods can lead to mudslides in mountainous regions, causing death to organisms in its path. (http://hurricanes.noaa.gov/prepare/rains.htm)
E>A>L>B: Hurricane winds often spawn tornadoes, which are smaller, more intense cyclonic storms that cause additional damage. This combination of winds, rain, and flooding can level a coastal town and cause significant damage to cities far from the coast. (http://www.howstuffworks.com/hurricane5.htm)
E>A>H>E: Flooding is often produced from the large amounts of rain dropped once the hurricane makes landfall. This can be intensified if the storm encounters another weather system. This occurred in 1969 when Hurricane Camille combined with an existing cold front in the mountains of central Virginia, dropping 30 inches of unexpected rain. (http://hurricanes.noaa.gov/prepare/rains.htm; http://earthobservatory.nasa.gov/Study/FloydIntro/)
Conclusion:
Hurricanes, created through interactions of the atmosphere and hydrosphere, impact each of the Earth’s spheres. The resulting damage could total billions of dollars or may even have the high price of death for some. Learning about hurricanes, how and where they move can help to hopefully prevent possible deadly devastation. Hurricanes are monitored more effectively due to technological advances.
Weather satellite images have improved our ability to detect and track severe weather. In 1999, NASA launched Quick Scatterometer (QuickSCAT) which uses specialized microwave radar to measure near surface wind speed and direction over the Earth’s oceans under all weather and cloud conditions greatly increasing available information. NASA’s Tropical Rainfall Measuring Mission (TRMM) was launched in 1997 with advanced computer instruments including precipitation radar, visible and infrared scanner, and lightning imaging sensors. Added to other weather observations and data, these data and images increase our ability to determine a storm’s location, direction, structure, and strength. Increased ability to understand the storm allows analysts time to warn the public in order to prepare for a storm’s arrival and potential threat. Hopefully, these technological advances will allow scientists to analyze the storms to determine the amount of energy released into the atmosphere and whether they affect global weather. (http://earthobservatory.nasa.gov/Library/Hurricanes/hurricanes_6.html; http://kids.mtpe.hq.nasa.gov/archive/hurricane/creation.html)
Although hurricanes are wild and furious and cannot be tamed nor stopped, they can be monitored and studied. Costly damage to property and lives could be mitigated by thorough preparation if communication is maintained to the public and life-saving measures are taken to prevent even more disasters and death.