RICHARDSON-NUMBER CONSTRAINTS FOR THE JUPITER AND OUTER PLANET WIND REGIME

Present theories of the dynamics of the outer planet atmospheres are l imited by the absence of direct observations of the wind and temperatu re layering below their visible cloud decks. We show that if the poten tial vorticity is assumed to be small at low latitudes. then cloud-tra cked wind measurements of the equatorial flow on Jupiter, Saturn, Uran us, and Neptune can be used to constrain their vertical stratification at deeper levels. A Richardson number between 1.2 and 4 is indicated for all the giant planets, which at their rapid rotation implies a muc h more vertical isentropic structure at these levels than is realized in the terrestrial atmospheres. These conditions signify the likely pr esence of a unique but as yet unstudied regime for the jovian meteorol ogy, illustrated by a new ''Richardson-Rossby'' diagram for comparativ e planetary circulations. The Jupiter case will be directly tested by the Galileo atmospheric entry probe.