Jupiter's Great Red Spot

Jupiter's Great Red Spot is a large swirling cloud mass of reddish-brown appearance (see figure in color plate section). Situated in Jupiter's southern hemisphere, it straddles the south tropical zone and, to the north of this, the south equatorial belt. The Great Red Spot (GRS) is roughly elliptical in shape, with the semi-major axis zonally aligned (east-west) and with dimensions approximately 22, 000 km (twice the diameter of the Earth) by 11, 000 km. The atmospheric motions associated with the GRS are visible in the cloud layer near the tropopause. It is generally agreed to be a vortex (Mitchell et aI., 1981); and Smith et aI. (1979a) give an estimate of the vorticity. This vortex is anticyclonic (rotating in the opposite sense to that induced by the planetary rotation), that is, anticlockwise, but with a weakly counter-rotating, or possibly quiescent inner region. The GRS is at high pressure and low temperature relative to its surroundings. A striking feature associated with the GRS is the turbulent oscillating cloud system to the northwest.