Tropical cyclones: Meteorological aspects

摘要

Sailors have long recognized the existence of deadly storms in tropical latitudes where the weather was usually a mix of bright sun and gentle breezes with quickly passing showers. These terrifying storms were known to have a core of screaming winds accompanied by blinding rain, spume and sea spray, and sharply lowered barometric pressure. When the sailors were lucky enough to survive penetration to the core of such violent weather, they found a region of calm. This region is the signature characteristic and best-known feature of these storms--the eye (Fig. 1). These violent storms of the tropical latitudes were known to be seasonal, hence their designation by Atlantic sailors as "line" storms, in reference to the sun' s crossing of the line (equator) in September (the month of peak hurricane activity in the North Atlantic). Later they became known there as hurricanes, named after Huracan, a Carib god of evil. In the Far East, over the waters of the western North Pacific, hurricanes are known as typhoons. Other local and regional names for these weather systems exist. To meteorologists, hurricanes and typhoons are recognized as a subset of the generic atmospheric phenomenon known as the tropical cyclone (TC). "Cyclone" refers to the direction of rotation of the wind around low-pressure areas--counterclockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere.