A dry February for southeastern Australia

For the 14-month period from January 2008 to February 2009, above average rainfall was recorded across most of the tropics, along with northeastern NSW and some areas of western WA. Rainfall was generally average to below average across the remainder of the country with much of Victoria experiencing very much below average rainfall. Victoria has experienced its second driest start to the year on record with SA experiencing its sixth driest start. For the 14-month period, areas of serious to severe rainfall deficiencies are evident in southern and western Victoria into southeastern SA, northern and eastern Tasmania, near Hobart, and in areas of central Australia.

The rainfall deficiencies map for the 21-month period from June 2007 to February 2009 shows areas of serious to severe deficiencies spread across mainly southeast Australia, with a few areas in central Australia. These deficiencies cover most of the agricultural areas of South Australia, much of central and western Victoria, and northern and eastern Tasmania. Small areas of lowest on record are evident on the Eyre Peninsula in SA and in the Wimmera district in Victoria. A dry February over much of southeast Australia has resulted in an increase of the area of severe deficiencies. Over the 21-month period the Top End and much of eastern Queensland and northeast NSW had some benefit from above average rainfall associated with the 2007/08 La Niña. Tropical rainfall has also been generally above average through the 2008/09 wet season. However, in southeastern and central Australia, apart from wet November and December periods in both 2007 and 2008, rainfall was generally below to very much below average.

The Indian Ocean Dipole (IOD) is a pattern of sea surface variability across the Indian Ocean that is associated with lower than normal rainfall over central and southern Australia when it is in a positive phase (see IOD). Both 2007 and 2008 were consecutive years of sustained positive IOD, which partly explains rainfall deficits through the 20-month period in these areas. The IOD usually has its greatest impacts between June and November.

The deficiencies discussed above have occurred against a backdrop of decade-long rainfall deficits and record high temperatures that have severely stressed water supplies in the east and southwest of the country. The combination of record heat and widespread drought during the past five to ten years over large parts of southern and eastern Australia is without historical precedent and is, at least partly, a result of climate change.