How Sensitive Is the Australian East Coast Low to Its Definition?

Abstract:

Midlatitude cyclones ("East Coast Lows", ECLs) are a major feature of Australia's east coast environment, and are both a cause of damaging severe weather and an important contributor to rainfall and dam inflow. For this reason, several studies in recent years have presented cyclone databases developed for this region from reanalysis data, using a variety of identification and tracking approaches. However, inconsistencies in base reanalysis data and low identification regions cause difficulties in selecting the appropriate database for a given purpose. For this study, the four cyclone identification and tracking methods from recent papers have been applied to the ERA-Interim reanalysis and restricted to an identical region and similar numbers of events. This allows a detailed comparison with a preexisting observational dataset between 1980 and 2006, with a particular focus on events associated with severe weather or explosive development. While all methods are able to detect the most severe events, large differences between methods are noted in both the observed seasonality and interannual variability of ECL occurrence. This has major implications for our understanding of the relationships between ECLs and major climate drivers such as ENSO, as well as long-term trends.