资源环境科技发展态势分析平台

Extratropical and subtropical cyclones, and their associated fronts, produce the majority of rainfall and extreme weather in the mid-latitudes around the world. In the Southern Hemisphere in particular, where observations are sparse, we have limited knowledge of their long-term variability and trends. While the long time period of the 20th Century Reanalysis (20CR) offers potential to assess longer-term changes, the lack of observational data sets makes it difficult to assess its reliability. We assess the skill of the 20CR at representing mid-latitude cyclones through a case study on the east coast of Australia. In this region, a comprehensive database has recently been developed of all severe floods between 1871 and 2012, of which >70% are associated with a coastal low-pressure system. Through use of the full 20CR 56-member ensemble, we are able to identify the majority of severe Australian east coast lows as early as the late 19th century, as well as recreate the cyclone tracks for some of the most severe events. The analysis shows that the full ensemble can be used for a long-term assessment of interannual variability in cyclone frequency from at least 1911, despite large inhomogeneities in the ensemble mean pressure fields.