Thermal structure and dynamics of the Jovian atmosphere 1. The great red spot

Abstract

Temperatures and thermal winds over the Great Red Spot (GRS) and its environs are derived from Voyager infrared spectroscopy (IRIS) data. The atmosphere over the GRS is characterized by a tropopause which is cold relative to its environment and an upper stratosphere which is relatively warm. The cold tropopause implies a decrease in anticyclonic vorticity with height above 500 mbar through the lower stratosphere. IRIS observations at 5 µm indicate little emission from the GRS itself, but enhanced emission in a ring about it, in agreement with recent ground‐based results. The behavior of the tropopause and 5 µm temperatures can be consistently interpreted as resulting from a circulation which rises within the GRS and subsides in the area around it. The explanation of the upper stratospheric temperatures is not so straightforward. A previous suggestion that they may be a manifestation of the linear vertical propagation of Rossby waves appears inconsistent with the gross east‐west symmetry in the stratospheric temperatures over the GRS. The implications of the present results for various theoretical models of the GRS are examined, and the possibility that latent heat release drives the GRS is discussed. Dynamical scalings based on an axisymmetric, frictionally controlled vortex suggest that, aside from the nonlinearities inherent in the parameterization of small‐scale moist convection, the large‐scale dynamics of the GRS are linear, as distinct from those of a tropical cyclone, which are markedly nonlinear.