Characterizing Regimes of Atmospheric Circulation in Terms of Their Global Superrotation

Abstract The global superrotation index S compares the integrated axial angular momentum of atmosphere to that a state solid-body corotation with underlying planet. is similar zonal Rossby number, which suggests it may be useful indicator circulation regime occupied by planetary atmosphere. We investigate utility for characterizing regimes atmospheric running idealized Earthlike general model experiments over wide range rotation rates Ω, 8Ω E Ω /512, where Earth’s rate, in both an axisymmetric and three-dimensional configuration. compute each simulated circulation, study dependence on Ω. For all considered, same order magnitude 3D experiments. high rates, ≪ 1 ∝ −2 , while at low ≈ 1/2 = constant. By considering limiting behavior theoretical models we show how value its local can related Indices define dominated geostrophic thermal wind balance, constant defines dynamics are characterized conservation within planetary-scale Hadley circulation. ≫ additional cyclostrophic balance strong equatorial not realized our simulations.