Cyclones
A violent storm originating over tropical or subtropical waters, characterized by violent rainstorms and high-velocity cyclonic winds between 5-25 degrees North and South from equator is called cyclone.
Tropical cyclones are like giant engines that use warm, moist air as fuel. That is why they form only over warm ocean waters near the equator. The warm, moist air over the ocean rises upward from near the surface. Because this air moves up and away from the surface, there is less air left near the surface. Another way to say the same thing is that the warm air rises, causing an area of lower air pressure below.Air from surrounding areas with higher air pressure pushes in to the low pressure area. Then that "new" air becomes warm and moist and rises, too. As the warm air continues to rise, the surrounding air swirls in to take its place. As the warmed, moist air rises and cools off, the water in the air forms clouds. The whole system of clouds and wind spins and grows, fed by the ocean's heat and water evaporating from the surface.Storms that form north of the equator spin counterclockwise. Storms south of the equator spin clockwise. This difference is because of Earth's rotation on its axis.As the storm system rotates faster and faster, an eye forms in the center. It is very calm and clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye.
When the winds in the rotating storm reach 39 mph, the storm is called a "tropical storm." And when the wind speeds reach 74 mph, the storm is officially a "tropical cyclone," or hurricane.
Hurricane Katrina
Hurricane Katrina was the USA's worst natural disaster that have ever happened. On 29th of August 2005 the terrible storm hit land hear New Orleans with speed up to 225km/h. This hurricane is priced as a category 4 hurricane. The battering winds were one of the dangers which affected the ocean to rise up by incredibly destroyable 9 meters tsunami.
The location of New Orleans is on the Missisippi delat in the Gulf of Mexico and most of the city is below sea level.
The location of New Orleans is on the Missisippi delat in the Gulf of Mexico and most of the city is below sea level.
The hurricane flooded 80% of the city and killed 1 800 people. It also damaged over 200 000 homes and made 800 000 people homeless. Economist said that Katrina cost the US economy over $80 billion.
Impact and social status of damage:
The most parts of Missisippi delta are sinking by a centimetre a year. Sea levels are rising at an accelerating rate and will be 2m higher by the 22nd century. Much of the delta is less than a metre above sea level so most communities will be submerged. The government is spending 1.5 billion $ over four years on wetland restoration. Another 15 billion $ is spent on defence for New Orleans. The cost of diverting Missisippi to save delta's wetlands and its settlements from sinking would be 200 billion $.
Impact and social status of damage:
- Median household income was 10 000$ less than the national average
- 20% of households had no car
- 25% of people were below the poverty line (doubled the national average)
The most parts of Missisippi delta are sinking by a centimetre a year. Sea levels are rising at an accelerating rate and will be 2m higher by the 22nd century. Much of the delta is less than a metre above sea level so most communities will be submerged. The government is spending 1.5 billion $ over four years on wetland restoration. Another 15 billion $ is spent on defence for New Orleans. The cost of diverting Missisippi to save delta's wetlands and its settlements from sinking would be 200 billion $.
Pictures of New Orleans after hurricane Katrina