6 Dynamics of Jupiter ' s Atmosphere

Jupiter has half a dozen eastward jet streams in each hemisphere. On average, Earth has only one in each hemisphere. Jupiter has weather patterns ("storms'') that last for centuries. Earth has stationary weather patterns fixed to the topography, but the average lifetime of a traveling storm is rvl week. Jupiter has no topography, i.e. , no cont inents or oceans; its atmosphere merges smoothly with the planet·s fluid interior. Absorbed sunlight (power per unit area) at Jupiter is only 3.3% that at Earth, yet Jupiter's winds are 3-4 times stronger. The ratio of Jupiter·s internal power to absorbed solar power is 0.7. On Earth the ratio is 2 X lQ4 . Jupiter's hydrologic cycle is fundamentally different from Earth's because it has no ocean, but lightning occurs on both planets. On Earth, electrical charge separation is associated with falling ice and rain. On Jupiter, t he separation mechanism is still to be determined. The winds of Jupiter are only 1/ 3 as strong as t hose of aturn and Neptune, and yet the other giant planets have less sunlight and less internal heat than Jupiter. Earth probably has the weakest winds of any planet, although its absorbed solar power per unit area is largest. All the giant planets are banded. Even Uranus, whose rotation axis is tipped 98° relative to its orbit axis. exhibits banded cloud patterns and eastwest (zonal) jets. All have long-lived storms, although Jupiter's Great Red Spot (GRS), which may be hundreds of years old, seems to be the oldest.