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From: Dorinda South
Date: 11/18/02
Time: 8:24:50 PM
Remote Name: 152.163.189.101
Is there anyone in our group that hasn't done a posting yet? Here is what our group (biosphere) came up with:
What is a hurricane?
A hurricane is a migratory tropical cyclone that originates over oceans near the equator. Usually, hurricanes form within a narrow equatorial belt with intermittent calms called doldrums. These doldrums have light variable breezes and frequent squalls, and they lie between the northeast and southeast tradewinds. Hurricanes do not occur in the South Atlantic Ocean because the doldrums of the Atlantic are north of the equator. Hurricanes occur in both the North and South Pacific Oceans because the Pacific doldrums extend North and South of the equator.
Hurricanes are made up of high-velocity winds blowing circularly around a low-pressure center called the eye of the storm. The eye develops when warm saturated air in the doldrums is forced upward by cooler, denser air. The atmospheric pressure drops sharply, and the wind velocity rises. Close to the point of lowest pressure, the winds will attain maximum force. The diameter of the area destructed by winds may exceed 240 km (150 mi). Gale winds may average 480km (300 mi) in diameter.
Hurricanes are rated on strength from a scale of 1 to 5. Category 1 is the mildest with winds of at least 120 km/h (74 mph). Category 5 is the strongest and rarest with winds exceeding 250 km/h (155 mph). In the eye of the storm, with an average diameter of 24 km (15 mi), the winds cease and clouds lift, but the seas remain extremely violent. (“http://encarta.msn/com/encnet/refpages/RefArticles.aspx?refid=7615659952”)
What is the biosphere?
The biosphere is the Earth’s thin zone of air, 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”)
Biosphere and Hurricane Interactions
E>B: Hurricanes are an important part of the natural scheme of things because they help clean out species that might otherwise dominate an ecosystem. They also stir up much needed oxygen in 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”)
E>B: 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. If the storm surge happens to synchronize with a high tide, it causes beach erosion and significant inland flooding. 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”)
B>E: Forecasters generally have a tough time figuring out how just strong a hurricane will ultimately become. New satellite data currently being developed may change all that. In the past, hurricanes snuck up on us. A tropical cyclone, or hurricane, would appear virtually out of nowhere, destroy whatever structures might lie in its path and suck unsuspecting coastal residents out to sea. While the damage potential of hurricanes hasn't changed over time, the monitoring of nature's greatest storms has improved dramatically. With such monitoring, humans can prepare themselves for future hurricanes and spare their lives. (“http://www.explorezone.com/archives/99_10/20_hurricane_satellites.htm”)
RESOURCES: “http://encarta.msn.com/encnet/refpages”
“http://encarta.msn/com/encnet/refpages/RefArticles.aspx?refid=7615659952”
(“http://www.explorezone.com/archives/99_09/20_hurricane_benefits.htm”)
(“http://www.explorezone.com/archives/99_10/20_hurricane_satellites.htm”)
(“http://www.howstuffworks.com/hurricane5.htm”)