Tropical Cyclone
TROPICAL CYCLONES
IN AUSTRALI
A
Tropical cyclone is one of the most common natural hazards in Australia. It’s also called ‘typhoon’, ‘hurricane’, ‘tropic storm’ and so on. If you look at the climatological data for tropical cyclone, you can find out that the actual shape of a tropical cyclone is almost the same as a whirlpool.
How could this amazing phenomenon happen? There’re several conditions needed to develop a tropical cyclone. Tropical cyclones are formed above the ocean surface, the temperature of the surface should be warm(above 26℃). The air should be very humid, usually 5℃ to 30℃. An unstable atmosphere condition (low-pressure system) is very important. This circumstance could develop the eye of the cyclone (vortex, the centre of the cyclone). As we know, the air in the high pressure area moves to the low pressure area. The eye of the cyclone is a low，high pressure area, this make the air around all moves to the vortex and become a cyclone. If this special condition remains, a tropical cyclone (hazard) will become a severe tropical cyclone (disaster, a mature tropical cyclone), which is really dangerous and destructive. There are five categories in cyclones and two general classifications (tropical cyclone and severe tropical cyclone), they are classified by the speed of the wind in the cyclone. When the speed of the wind is under 125km/h, which is known as a tropical cyclone, a hazard, is the first category. When the wind speed gets higher, the cyclone will be destructive, and may become a disaster (tropical cyclone (125~169km/h), severe tropical cyclone (170~224km/h), severe tropical cyclone (225~279km/h), severe tropic cyclone (over 280km/h). A cyclone (hazard) may not be destructive, however a mature tropical cyclone (a severe tropical cyclone) would be extremely dangerous. A fatal flood may form by a tropical cyclone. Since 1839, tropical cyclones have taken away over 2100 lives in Australia. The annual cost of
IN AUSTRALI
A
Tropical cyclone is one of the most common natural hazards in Australia. It’s also called ‘typhoon’, ‘hurricane’, ‘tropic storm’ and so on. If you look at the climatological data for tropical cyclone, you can find out that the actual shape of a tropical cyclone is almost the same as a whirlpool.
How could this amazing phenomenon happen? There’re several conditions needed to develop a tropical cyclone. Tropical cyclones are formed above the ocean surface, the temperature of the surface should be warm(above 26℃). The air should be very humid, usually 5℃ to 30℃. An unstable atmosphere condition (low-pressure system) is very important. This circumstance could develop the eye of the cyclone (vortex, the centre of the cyclone). As we know, the air in the high pressure area moves to the low pressure area. The eye of the cyclone is a low，high pressure area, this make the air around all moves to the vortex and become a cyclone. If this special condition remains, a tropical cyclone (hazard) will become a severe tropical cyclone (disaster, a mature tropical cyclone), which is really dangerous and destructive. There are five categories in cyclones and two general classifications (tropical cyclone and severe tropical cyclone), they are classified by the speed of the wind in the cyclone. When the speed of the wind is under 125km/h, which is known as a tropical cyclone, a hazard, is the first category. When the wind speed gets higher, the cyclone will be destructive, and may become a disaster (tropical cyclone (125~169km/h), severe tropical cyclone (170~224km/h), severe tropical cyclone (225~279km/h), severe tropic cyclone (over 280km/h). A cyclone (hazard) may not be destructive, however a mature tropical cyclone (a severe tropical cyclone) would be extremely dangerous. A fatal flood may form by a tropical cyclone. Since 1839, tropical cyclones have taken away over 2100 lives in Australia. The annual cost of
Bibliography: The C.G. textbook (Australian explorations) http://www.bom.gov.au/cyclone/about/tc-checklist.shtml