Australian Southerly Busters. Part II: The Dynamical Structure of the orographically

Abstract

A methodology is presented for comparing nonlinear 3D model output to the physical principles embodied in idealized and analytical models, through the use of the transformation of wind components (v, vg,va) to accelerations k/f?(?fk?v,?p/?dv/dt. This methodology is applied to numerical simulations of the interaction of a cold front with coastal topography, leading to the formation of a ?southerly busier? current along Australia's east coast. It is found that while the front is moving along the south coast mountain chain, the dynamics of the perturbation are similar in character to an orographically trapped density-current-type perturbation on the background front. Along the east coast, however, the southerly busier current bears no dynamical relationship to either an orographically trapped density current or a Kelvin wave, the balance of forces here being dominated by inertial terms.