LOW-LEVEL JET SIMULATION OVER THE SOUTHERN-OCEAN IN ANTARCTICA

We have examined the dynamical characteristics of an intense topograph ic low level jet (LLJ) that develops in high-resolution numerical simu lations of airflow in the Antarctic region. The jet forms off Cape Ada re (Victoria Land) over the Southern Ocean, when a large scale cyclone is present in the region of the Ross Sea and adjacent ocean. A low le vel easterly airflow is directed towards the portion of Transantarctic Mountains located along the west coast of the Ross Sea, inducing a ba rrier wind airflow which is locally parallel to the topographic barrie r. By means of numerical experiments and model output diagnostics, we have investigated the time evolution of different meteorological param eters, and in particular those relevant for the vorticity budget, asso ciated with the LLJ formation. The vertical component of relative vort icity, locally generated mainly by tilting above the boundary layer, i s advected downstream creating vorticity streaks extending to the nort h over the Southern Ocean. The emerging picture is generally consisten t with low Froude number regimes of flow over topography. However, com plexities in topography geometry and in the large scale flow configura tion do not allow direct comparison with existing theories based on si mplified models.