Investigation of the thermal structure above selected cloud features in the Jovian atmosphere, making use of Voyager IRIS data, reveals strong similarities among a broad range of features which differ considerably in visual appearance. The atmosphere above anticyclonic features, including the major white ovals, the Great Red Spot, and a zone, are cold relative to the immediate surroundings in the upper troposphere region. These results are consistent with upwelling and divergence in this part of the atmosphere. In contrast, a 'hot spot' and a 'barge' which are localized cyclonic features, are found to be warm relative to their surroundings, implying subsidence with accompanying convergence. In all cases, the thermal wind shear associated with the features indicates a decay of the vorticity with height in the upper troposphere and lower stratosphere. Vertical velocities inferred from the observed temperature pertubations imply an upper limit of vertical mixing times near the tropopause of ~20 years. Temperatures in the upper stratosphere above the anticyclonic features show considerable variation, but in most cases are found to be relatively warm. At the present time, no satisfactory explanation for this behavior appears to exist. |