Critical comparison of the cyclone activity in the Amundsen, Bellingshausen and Weddell sectors of the Antarctic as diagnosed in 15 tracking algorithms
Ian Simmonds

Authors

Simmonds I and Rudeva I
The University of Melbourne

Abstract

The region around Antarctica is one of very high baroclinicity and large surface heat fluxes. These characteristics induce a never-ending progression of intense cyclones over, and to the north of, the sea ice zone. The quantitative diagnosis of these storms is a key component of understanding Antarctic weather and climate and the poleward transport of energy.

Our group is part of an international consortium, IMILAST (Intercomparison of mid latitude storm diagnostics – www.proclim.ch/imilast/index.html) formed to compare and assess the wide range of automatic cyclone tracking schemes that are readily available to the scientific community. This group has identified all cyclones appearing in the ERA-Interim global reanalysis in 15 state-of-the-art identification algorithms. Each of these algorithms make specific (and often quite different) choices in their cyclone 'search' method. These differences include 'topographic masking' and how cyclones are identified in regions of strong topographic slopes and curvature. These issues are of particular relevance in the immediate environs of the Antarctic continent.

To have confidence in compilations of subantarctic cyclone behaviour and trends it is clearly of importance to identify the respects in which different algorithms might show sensitivity to specific elements of their design. We have taken advantage of our participation in IMILAST (and its collection of tracking schemes) to explore the similarities and differences in the cyclone statistics revealed in the algorithms. Particular attention will be focused on the key Amundsen-Bellingshausen sector (60°S-coast, 180-300°E) and Weddell sector (60°S–coast, 300-360°E).