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A.J. Friedson, G. S. Orton (JPL/Caltech), J.L. Ortiz (Inst. Astrofisica d'Andalucia)
Ortiz et al. (1998) found that (i) the confinement of Jovian 5-micron hot spots to a narrow range of latitudes near 6.5\circN, (ii) their propensity to occur in 8 or 9 quasi-evenly-spaced longitudinal areas, and (iii) the simultaneous changes with time observed in the propagation speed and dominant zonal wavenumber of the hot spot pattern, all could be explained if the hot spots are associated with an equatorially trapped Rossby wave of degree 1 drifting with a westward phase speed between 99 and 103 meters per second relative to the System III longitude system. The unusual cloud opacity and tracer mixing ratio profiles in the hot spots (Niemann et al. 1996, Showman and Ingersoll 1998) suggest they may be areas characterized by strong subsidence. Here we explore whether overturning of an equatorial wave in a weakly stable, deep troposphere might trigger strong downwelling in localized regions. We model the wave as a linear perturbation superimposed on a zonal mean basic state. The large vertical wind shear measured by the Galileo Probe is included in the basic state, but the horizontal shear of the equatorial jet is ignored in these preliminary calculations.
Niemann, H.B., et al., 1996. Science 272, 846-848. \\ Ortiz, J.L., et al. 1998. J. Geophys. Res., in press. \\ Showman, A.P. and A.P. Ingersoll 1998. Icarus 132, 205-220.