Planetary scientists have long puzzled over why fast-movingrivers of air called jet streams flow eastward at the equator of Jupiter andSaturn, but go westward on Uranus and Neptune. Now a new simulation has begununraveling that mystery by showing how turbulent thunderstorms create the jetstreams.
Whether a jet stream flows east or west seems to dependon the amount of water vapor in a planet's atmosphere — but researchers confessthat the "how" stilleludes them.
"Under these conditions, the eastward equator flowprefers low water vapor abundance," said Yuan Lian, an atmosphericdynamics researcher at the University of Arizona in Tucson. "The westwardequator flow prefers high water vapor abundance. However, we still don't knowexactly how this happens."
Jet streams feed on swirling eddies that can form thebasis of thunderstorms on giant planets. Eddies don't necessarily all mergetogether to form a jet stream — some can simply spin off their angular momentuminto the jet to sustain howling wind speeds.
"You have a little vortex that gets stretched outand sheared apart by the wind," said Adam Showman, a planetary scientistat the University of Arizona. "As it's shearing apart, it gives the jetstream a little push."
"We took our best guess with our best models foreach of the planets," Showman told SPACE.com. "We did a bunchof simulations varying the water. Even if we don't think the planet has thatamount, it allows us to understand role of water in that simulation."
"When you have this occurring in a complicated 3-Dcirculation, it can develop latitudinal temperature differences," Showmannoted. "More water vapor means more temperature differences that changethe stability of the atmosphere."
"We want to include as many factors as we can,"Lian said. "That way, we can probably produce jet speeds similar toobservations."
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