The spontaneous emergence of coherent vortices and alternating hot-and-cold latitude bands in an idealized GCM

Three-dimensional simulations of the atmospheric flow on giant planets using a primitive equation dry GCM show that long-lived coherent vortices can spontaneously emerge and they play an important role in creating alternating hot-and-cold latitude bands, which correlate with the jets. The GCM uses idealized Held-Suarez physics: the forcing is a linear relaxation of temperature field to a prescribed temperature profile, which decreases monotonically poleward and represents differential radiation; the dissipation is a linear damping of momentum near the surface. The vortices have very distinct vertical structures. For anticyclonic vortices, they have warm cores near the surface and cold cores near the upper atmosphere, caused by a strong downdraft in anticyclones. The cyclonic vortices are the reverse as the anticyclones, but they are weaker in agreement with the preference for anticyclones in shallow water models. The anticyclonic and cyclonic vortices have different preferred latitude bands, organizing themselves into having the same sign of vorticity as the jets. The anticyclonic vortices prefer the 'zones' (jets with anticyclonic wind shear) and therefore make the 'zones' warmer than the surrounding 'belts' (jets with cyclonic wind shear) near the surface. Energy spectrum analysis shows that the large vortices are driven by inverse energy cascade from smaller vortices, and these large vortices are converting eddy kinetic energy into potential energy. This tendency is also observed for shallow water decaying turbulence and we provide it an explanation based on the invariants of the shallow water system. Additional simulations using a more comprehensive GCM with parameters relevant for Jupiter show similar behavior. Typical instantaneous temperature field near the surface (975 mb) together with wind field at upper atmosphere (250 mb) . Only wind vector at the place where the magnitude of relative vorticity is larger than 10e(-5)/s is shown. The color of the wind vector indicates the sign of vorticity, with green indicating anticyclonic and yellow indicating cyclonic.