A case study of a midtropospheric subsynoptic-scale cyclone that developed over the Ross Sea and Ross Ice Shelf of Antarctica

Abstract

Satellite imagery, synoptic-scale analyses and automatic weather station data were used to study a subsynoptic-scale cyclone that developed over the Ross Sea and Ross Ice Shelf areas of Antarctica. A pre-existing subsynoptic-scale midtropospheric cyclone descended from southern Victoria Land into the semi-permanent baroclinic environment over the south-western corner of the Ross Sea. The subsynoptic-scale cyclone then developed into a frontal system travelling south-eastward over the Ross Ice Shelf and decayed five days later over Marie Byrd Land. It is concluded that stretching of the subsynoptic-scale low, while descending over 2000 m from the high plateau down to sea level, increased its cyclonic vorticity via conservation of potential vorticity. This, along with a cold katabatic outbreak into the northern part of the circulation, provided the mechanisms for its initial development. Subsequently, cold boundary-layer air over the Ross Ice Shelf spiralled into the subsynoptic-scale cyclone supporting its further development. An upper-level synoptic-scale cyclone that approached the area provided the upper-level support for its ESE displacement and development.