Atypical influence of the 2007 La Nina on rainfall and temperature in southeastern Australia

Interannual climate variations associated with El Nino - Southern Oscillation (ENSO) dominate rainfall and temperature variability in southeastern Australia's Murray-Darling Basin (MDB), an important region for agricultural productivity. Following a decade-long dry period, a La Nina during 2007 failed to provide above average rainfall and cool temperatures in the southern half of the MDB, typical of most La Nina events for the region. Instead, annual (winter halfyear) rainfall was 17% (35%) below average and maximum temperatures 0.91 degrees C (1.26 degrees C) above average. Based on the past variability between La Nina events, the combined probability of such anomalies is less than 2%. It is likely that these anomalies contain some contribution from a positive Indian Ocean Dipole (IOD). However, the IOD and other large-scale circulation features are unlikely to explain the atypical conditions that occurred in the southern MDB during the 2007 La Nina. Citation: Gallant, A. J. E., and D. J. Karoly ( 2009), Atypical influence of the 2007 La Nina on rainfall and temperature in southeastern Australia, Geophys. Res. Lett., 36, L14707, doi: 10.1029/2009GL039026.