An Investigation of the Links between ENSO Flavors and Rainfall Processes in Southeastern Australia

The causes of rainfall variations in southeastern Australia associated with three key El Nino years (1982, 1997, and 2002) are explored. Whereas 1982 and 2002 were exceptionally dry years, 1997 had near-average rainfall. These variations in rainfall can be explained by changes in the behavior of cutoff low pressure systems. Although each year had a similar number of cutoff low events, 1997 had higher rainfall per cutoff low event when compared with the other years. In particular, rain in 1997 is attributable to five large wet events from cutoff low pressure systems. In each of these wet events, the moist air originated from the marine boundary layer off the coast of northeastern Australia. Cutoff lows in 1982 and 2002 were much drier and did not draw in moist air from the northeastern coast. In typical classifications, 1982 and 1997 are grouped together as "canonical" El Ninos whereas 2002 is a Modoki El Nino. The results presented here imply that these groupings are not definitive in explaining variations in southeastern Australian rainfall.