Low-level jet simulation over the Southern Ocean in Antarctica

Abstract

We have examined the dynamical characteristics of an intense topographic low level jet (LLJ) that develops in high-resolution numerical simulations of airflow in the Antarctic region. The jet forms off Cape Adare (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 level easterly airflow is directed towards the portion of Transantarctic Mountains located along the west coast of the Ross Sea, inducing a barrier wind airflow which is locally parallel to the topographic barrier. By means of numerical experiments and model output diagnostics, we have investigated the time evolution of different meteorological parameters, and in particular those relevant for the vorticity budget, associated with the LLJ formation. The vertical component of relative vorticity, locally generated mainly by tilting above the boundary layer, is advected downstream creating vorticity streaks extending to the north over the Southern Ocean. The emerging picture is generally consistent with low Froude number regimes of flow over topography. However, complexities in topography geometry and in the large scale flow configuration do not allow direct comparison with existing theories based on simplified models.