威望 1293 点
TheMighty Pinwheel Takes Shape.
Theaverage hurricane is about 340 miles (550 km) across and 9 miles (15 km ) high,it might contain 25,000 times the energy of an ordinary summer thunderstorm, orone-fifth of the world’s energy needs for a year. Smaller ones, such asCamille, in 1969, and Andrew, in 1992, often are the most powerful.
Ahurricane’s energy gets concentrated towards the center of the hurricanespiral, known as the eye. As air gets sucked inward in the lower reaches of thehurricane, it spirals more and more tightly toward the center. The eye of thehurricane attracts the winds because that’s where warm air is rising andleaving the storm the fastest. As a result, it is the area of the lowest airpressure.
Ahurricane’s winds are strongest just outside the center. They actually circlethe eyewall, a barrier of thick clouds where the winds abruptly spiral upward,leaving the center of the hurricane magically calm and often sunny. The eye ofa hurricane can be 20 to 30 miles (32---48 km) across. People living in thepath of a hurricane’s eye will experience ferocious winds and rain, thensuddenly placid weather, and then, just as suddenly, rain and howling windsfrom the opposite direction, or the trailing side of the hurricane.
Theeyewall has a steeply conical shape. Winds spiral more widely around it as theyrise and slow down near the top. The warmest air in a hurricane is often foundnear the highest point in the eye, it might be as much 300F (160 C) warmerthan the low-level, outer reaches of the storm. This may be where hurricanes,so tremendously destructive below, show their value. By dispersing heat carriednorthward from the equator, hurricanes help spread tropical warmth to coolerparts of the grope.
If thehurricane makes landfall, it may topple trees, power lines, and buildings, wipeout islands and beaches, tear up roads, and bring a storm surge that caninundate cities and farms, even miles inland. The flooding is almost always themost damaging result of a hurricane, ruining drinking water supplies andcreating a high risk of injury and disease by carrying debris, sewage, and deadanimals.