A CASE-STUDY OF A MIDTROPOSPHERIC SUBSYNOPTIC-SCALE CYCLONE THAT DEVELOPED OVER THE ROSS SEA AND ROSS ICE SHELF OF ANTARCTICA

Satellite imagery, synoptic-scale analyses and automatic weather stati on data were used to study a subsynoptic-scale cyclone that developed over the Ross Sea and Ross Ice Shelf areas of Antarctica. A pre-existi ng subsynoptic-scale midtropospheric cyclone descended from southern V ictoria Land into the semi-permanent baroclinic environment over the s outh-western corner of the Ross Sea. The subsynoptic-scale cyclone the n developed into a frontal system travelling south-eastward over the R oss Ice Shelf and decayed five days later over Marie Byrd Land. It is concluded that stretching of the subsynoptic-scale low, while descendi ng over 2000 m from the high plateau down to sea level, increased its cyclonic vorticity via conservation of potential vorticity. This, alon g with a cold katabatic outbreak into the northern part of the circula tion, provided the mechanisms for its initial development. Subsequentl y, 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 up per-level support for its ESE displacement and development.