Climatological aspects of cyclogenesis near Adélie Land Antarctica

Abstract

The Ad´elie Land coastal region of Antarctica is one of the most prominent cyclogenesis regions in the Southern Hemisphere, and is adjacent to the continent’s most intense katabatic wind regime. However, the physical mechanisms responsible for cyclogenesis are not known. A manual analysis of cyclogenesis for the 2003–2005 period using output from the Antarctic Mesoscale Prediction System (AMPS) identifies two primary patterns of cyclogenesis near the Ad´elie Land coast. For “secondary development” cyclones, enhanced low-level cyclonic vorticity and baroclinicity result from the combination of an existing synoptic-scale cyclone to the west, coastal barrier winds and katabatic winds. “Lee cyclogenesis” occurs near 152◦E on the cyclonic-shear side of the Ad´elie Land katabatic jet, where a low-level warm potential temperature anomaly sets up a lee trough that becomes mobile with the arrival of upper-level synopticscale forcing. The representation of both “secondary development” and “lee cyclogenesis” cyclones in an automated cyclone-tracking scheme is explored, where it is found that the automated scheme overestimates cyclogenesis for this region. The location of the Antarctic coastal cyclogenesis maximum near Ad´elie Land is due to the unique juxtaposition of the extraordinary katabatic wind regime and dissipating synoptic-scale cyclones to the west.