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Jet Streams On Earth and Jupiter
By Robert Roy Britt
Senior Science Writer
posted: 01:41 pm ET
09 February 2000
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jupiter_sidebar_000209 High-speed winds race around the globe between four and six miles above the Earth, mostly from west to east. These rivers of air are often collectively referred to as the jet stream, and they form at the boundaries of warm and cold air. Speeds average between 50 and 100 m.p.h. (80 and 160 kilometers per hour), but reach 250 m.p.h.(400 kilometers per hour). There are actually three (sometimes two) major jet streams over North America in winter, stretching from Canada to the subtropics. These separate bands of wind snake about, separating and combining at various times. The course of the fast winds affect air masses, which in turn affect the course of the winds. Winter storms tend to track along the jet streams. A storm's energy, in the form of increased thunderstorm activity, alters the path of the polar jet stream, typically kicking it further north, where it can block Arctic air from moving into the East. On Jupiter, there are more jets -- five in each hemisphere, according to Caltech's Andrew Ingersoll. The Jovian jets zip along at up to 300 m.p.h. (483 kilometers per hour), and the move east to west in a more consistent manner than their gyrating, ever-changing terrestrial cousins. On Jupiter, the jets control the planet's bands of color. "The jets produce patterns of upwelling and downwelling that bring chemicals up from Jupiter's interior," Ingersoll explained. "Some of the chemicals condense to form clouds. Depending on the rate of updraft and other factors, the clouds can have different colors." Jupiter's jets, along with massive thunderstorms that roil across the surface, are fueled by the planet's ability to generate heat from within, the result of a store of compressed hydrogen in its center. Researchers say Jupiter is gradually cooling, a process likely to continue for another five billion years or so.
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