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Brown dwarfs and directly imaged exoplanets exhibit observational evidencefor active atmospheric circulation, raising critical questions about mechanismsdriving the circulation, its fundamental nature, and time variability. Ourprevious work demonstrated the crucial role of cloud radiative feedback ondriving a vigorous atmospheric circulation using local models that assume aCartesian geometry and constant Coriolis parameters. In this study, we explorethe properties of the global dynamics. We show that, under relatively strongdissipation in the bottom layers of the model, horizontally isotropic vorticesare prevalent at mid-to-high latitudes while large-scale zonally propagatingwaves are dominant at low latitudes near the observable layers. The equatorialwaves have both eastward and westward phase speeds, and the eastward componentswith typical speeds of a few hundred m/s usually dominate the equatorial timevariability. Lightcurves of the global simulations show variability withamplitudes from 0.5 percent to a few percent depending on the rotation periodand viewing angle. The time evolution of simulated lightcurves is criticallyaffected by the equatorial waves, showing wave beating effects and differencesin the lightcurve periodicity to the intrinsic rotation period. The verticalextent of clouds is the largest at the equator and decreases poleward due tothe increasing influence of rotation with increasing latitude. Under weakerbottom dissipation, strong and broad zonal jets develop and modify wavepropagation and lightcurve variability. Our modeling results help to explainthe puzzling time evolution of observed lightcurves, a slightly shorter periodof variability in IR than in radio wavelengths, and the viewing angledependence of variability amplitude and IR colors.

Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: global and equatorial dynamics