臺(tái)風(fēng),龍卷風(fēng)的ppt

單擊此處編輯母版標(biāo)題樣式,單擊此處編輯母版文本樣式,第二級(jí),第三級(jí),第四級(jí),第五級(jí),*,Forms,Measures,Definition,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 Pacific 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(,地球自轉(zhuǎn)偏向力,)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,cloud-free spot.Surrounding the eye is the,eyewall,an area about 16 kilometres to 80 kilometres wide in which the strongest,thunderstorms,and 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 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(,積雨云,)cloud or,in rare cases,the base of a cumulus 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 thunderstorm 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 from windows.,Get out of automobiles.,Do not try to outrun a tornado in your car;instead,leave it immediately.,Thank you!,