Sensitivity of a simple atmospheric model to changing surface friction with implications for seasonal prediction

An ensemble of idealized experiments with the simplified general circulation model PUMA is used to analyze response reduced surface friction, that a strengthening eddy-driven jet, weakening Eulerian mean overturning, and suppression baroclinic instability. The instability caused by an effect called barotropic governor which increased horizontal shear restricts ability disturbances convert available potential energy into kinetic energy. This ensures residual Eliassen–Palm flux (EP flux) divergence are largely invariant friction parameter despite connection between eddy-momentum flux. leads increase in persistence measured period peak variance on synoptic time-scales strengthened signal-to-noise ratio seasonal time-scales. These findings suggest paradox seen context prediction can be excess mechanical damping atmospheric systems inhibiting effect.