The 5th Conference on Polar Meteorology and Oceanography

2.2
CYCLOGENESIS MECHANISMS WITHIN THE ANTARCTIC CIRCUMPOLAR TROUGH

John Turner, British Antarctic Survey, Cambridge, UK; and S. Leonard and L. Yeomans

Automatic analysis of fields from operational NWP systems and visual assessment of satellite imagery has shown that the circumpolar trough, which rings the Antarctic between the latitudes of 60-70 degrees South, is the area of the Southern Hemisphere where the greatest number of synoptic-scale depressions are located. Some of these lows develop in mid-latitudes and move polewards before declining within the trough. However, both the satellite imagery and the model fields indicate that the circumpolar trough is a region where many cyclogenesis events take place on a range of scales and the model results suggest that more synoptic-scale cyclogenesis events take place here than anywhere else in the Southern Hemisphere. This paper will present the results from a detailed analysis of one month's cyclogenesis events within the circumpolar trough in the vicinity of the Antarctic Peninsula. The study had the goal of understanding the mechanisms that are important for the development of these lows and to reconcile the information available from the satellite and model data. The month of March 1993 was chosen for this work so that geophysical quantities could be derived from passive microwave data over the ocean areas when the sea ice was at a minimum. Other data used within the study included AVHRR full resolution imagery and fields from operational NWP models. The talk will briefly cover the climatological occurrence of cyclogenesis during the month and then describe in detail several individual developments, concentrating on the mechanisms that are important for cyclogenesis within the circumpolar trough. The talk will also consider the degree to which the NWP models are able to represent the cyclogenesis events in this data-sparse region of the Southern Ocean

The 5th Conference on Polar Meteorology and Oceanography