飓风tropical cycloneSevere atmospheric disturbance in tropical oceans.Tropical cyclones have very low atmospheric pressures in the calm, clear centre (the eye) of a circular structure of rain, cloud, and very high winds. In the Atlantic and Caribbean they are called hurricanes; in the Pacific they are known as typhoons. Because of the Earth's rotation, tropical cyclones rotate clockwise in the Southern Hemisphere and counterclockwise in the Northern. They may be 50–500 mi (80–800 km) in diameter, and sustained winds in excess of 100 mph (160 kph) are common. In the eye, however, the winds drop abruptly to light breezes or even complete calm. The lowest sea-level pressures on Earth occur in or near the eye. 热带气旋 tropical cyclone在热带海洋上形成的剧烈大气扰动。热带气旋中心(眼)的低气压带是晴朗平静的好天气，外部则环绕着降雨、云和强风。在大西洋和加勒比海的热带气旋被称作飓风，而在太平洋则被称作台风。由于地球的自转，热带气旋在南半球按顺时针方向运动，而在北半球则按逆时针方向运动。它们的直径可达到80～800千米，一般风速可保持在每小时160千米。但热带气旋的中心则只有微风甚至是平静的海面。地球上最低的海洋气压出现在热带气旋的中心或中心附近。气旋出现在热带纬度，由温暖的空气和水驱动。风环绕低压中心“风眼”转动，中心通常无风。在风眼壁里面或附近风雨通常最为猛烈。
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