Cyclonically Forced Barrier Winds along the Transantarctic Mountains near Ross Island

Abstract

The effect of the Transantarctic Mountains on cyclonically forced boundary-layer winds in the vicinity of Ross Island, Antarctica (77.5°S, 167°E), is discussed. When cyclones are present over the western Ross Ice Shelf and Ross Sea, the low-level easterly airflow is toward the mountains. A barrier wind regime is set up as the flow is turned northward and becomes parallel to the mountain range. IT is found that cyclonically forced barrier winds occurred around 5% and 8% of the time during 1984 and 1985, respectively. The case histories of two well-defined barrier wind events lasting for 24 h are discussed in detail, with regional analyses based on satellite photographs and automatic weather station data. One case is for a katabatic wind-forced mesoscale cyclone forming to the north of Ross Island, and the other is for a synoptic-scale cyclone moving through the western Ross Ice Shelf-Ross Sea region. A numerical model for the vertically integrated boundary-layer flow that calculates two horizontal velocities and the boundary-layer depth is used to investigate the mountain barrier effect on low-level airflow. The domain is the region of the western Ross Ice Shelf-Ross Sea from 82° to 76°S, between Byrd Glacier and Terra Nova Bay, and bounded to the west by the Transantarctic Mountains. The boundary-layer airflow is constrained to remain below the height of the mountains, so that the surface airflow is around the topographic features of Minna Blulff and Ross Island. The two cases of cyclonic forcing are modeled, with the isobars intersecting the mountains obliquely. The model depicts the pressure increases and stagnation zones south of Minna Bluff and Ross Island, and the surface airflow eastward past these features, which agree with observations.