Why do some of the gas giant planets show significant atmospheric banding and large oval shaped storms?

Question

Why do some of the gas giant planets show significant atmospheric banding and large oval shaped storms?

Answer 1

The atmospheric banding evident on planets such as Jupiter and Neptune is the result of convection.  Convection, in this context, is the transfer of heat between the interior of a planet and its atmosphere.  Because the gas giants possess interior regions of compressed gases that are under tremendous pressure, heat is generated and radiates outward from the planetary interior and into the atmosphere.  This energy fuels the development and maintenance of "jets" within the atmospheres of the gas giants, because the atmospheric temperature differences fostered by the stronger and weaker convective currents create pressure differences that drive motion.  The result is jets that consist of streams of gas that move significantly faster than the surrounding fluid.  Convective currents allow gaseous elements from the planetary cores to be upwelled into the jets, leading to the creation of brilliantly colored bands that consist of hydrogen and ammonia gas.

The oval-shaped storms are caused by planetary rotation.  The Coriolis "force" is a natural tendency of rotating gaseous parcels to be deflected to the right of their direction of motion in the northern hemisphere of a planet and to the left of their direction of motion in the southern hemisphere of a planet.  This mechanism fosters curvature of the gaseous medium and allows for the formation of hurricanes and other cyclones on Earth.  Indeed, the oval-shaped storms visible in the atmospheres of the gas giants are simply giant editions of the more familiar Earth-based cyclones.  Because planets such as Jupiter are more massive and rotate more rapidly than Earth, however, the Coriolis "force" is stronger on these planets and allows for the production of much more powerful cyclones.