台风,龙卷风的ppt.ppt

1、Whats the definition ?,Hurricane and Typhoon,Same : both of them are a special kind of tropical cyclone , and a storm system. Different : happen in different places ,so they have different name. Hurricane : occur in North Atlantic Ocean, the Caribbean Sea ,the Gulf of Mexico , or the Northeast Pacif

2、ic Ocean Typhoon: Northwest Pacific Ocean west of the International Date Line,six main requirements for hurricane to form and develop: . sufficiently warm sea surface temperatures . atmospheric instability . high humidity in the lower to middle levels of the troposphere . enough Coriolis force(地球自转偏

3、向力) to develop a low pressure center . a pre-existing low level focus or disturbance . low vertical wind shear,The eye of hurricane,The eye, is an area of relative calm (and lowest atmospheric pressure) at the center of circulation. The eye is often visible in satellite images as a small, circular,

4、cloud-free spot. Surrounding the eye is theeyewall, an area about 16 kilometres to 80 kilometres wide in which the strongestthunderstormsand winds circulate around the storms center.,Hurricane Categories,Category one - Winds 74-95 mph. Category two - Winds 96-110 mph. Category three - Winds 111-130

5、mph. Category four - Winds 131-155 mph. Category five - Winds greater than 155 mph.,Tornado,The definition of Tornado,A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus(积雨云) cloud or, in rare cases, the base of a cumulus

6、 cloud.,Place：most frequently in the United States east of the Rocky Mountains Time: spring and summer Forms : multiple-vortex tornado waterspout landspout,A change in wind direction and increase in wind speed an invisible, horizontal spinning effect in the lower atmosphere raising air within the th

7、understorm updraft tilts the rotating air from horizontal to vertical rotation（ 2-6 miles wide ） rotating wall cloud a strong tornado develops,What should we do ？,environmental clues make a family plan Before the storm have frequent drills listen to radio and TV,If a Warning is issued or if threatening weather approaches: In a home or building, move to a pre-designated shelter, such as a basement. If an underground shelter is not available, move to an interior room or hallway on the lowest floor and get under a sturdy piece of furniture. Stay away fr