|
For the 12 and 18-month periods ending 31st December 2008
Short-term rainfall deficiencies ease over much of Australia
LINKS:
Rainfall deficiencies definition
12-month rainfall deficiencies
18-month rainfall deficiencies
Above to very much above average rainfall over most parts of Australia during November and
December 2008 has resulted in a significant reduction in the total area of short-term rainfall
deficiencies. Drought periods of less than 12 months generally show only small and isolated
areas with rainfall totals in the lowest 10% of historical records.
For the 12-month period from January to December 2008, above average rainfall was recorded
across the Top End, eastern Queensland, northeast NSW and far west parts of WA. Rainfall was average to
below average across the remainder of the country. For this period, areas of serious to severe rainfall
deficiencies are evident in central and western Victoria, eastern Tasmania, near Hobart, parts of western
Queensland and in areas across the central NT.
The La Niña conditions that developed during 2007 resulted in a wet start to 2008 across the Top
End and most of eastern Australia. However, during autumn the La Niña weakened, coinciding with the
failure of autumn rains in many areas. When averaged across the southern half of the country it was
the second driest autumn since records began in 1900. Winter rains were mixed, while spring started
with well below average rains across most of the southeast.
Low annual rainfall over the southern Murray Darling Basin further exacerbated the long dry spell in this
region and a drier than normal autumn and spring for southeast Australia severely stressed farming activity
and water supplies in these areas. A dry autumn for southern WA also significantly impacted on farming practices
and water supplies in this region.
The rainfall deficiencies map for the 18-month period from July 2007 to December 2008 shows
serious to severe deficiencies in areas across southeast Australia, western Queensland and central Australia.
A small area of lowest on record is evident near Hobart. Over the 18-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.
However, in southeastern Australia, central Australia and western Queensland, 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 18-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.
For more information go to a recent
Special Climate
Statement on the long-term drought in southern Australia "Long-term rainfall deficiencies continue in southern Australia while wet conditions dominate the north",
issued 10 October 2008. A dry October over much of southeastern Australia has, in many cases, increased the magnitude of the three and seven year records
at the stations identified in the statement, and more stations have set three-year records, especially in Tasmania.
More information on the climate of Australia during 2008 can be obtained from the
Annual Australian Climate Statement.
Rainfall
deficiency maps for standard periods out to three years are
available.
Note: The terms used to describe rainfall in these
Drought Statements have the following meanings -
Serious deficiency
- rainfalls in the lowest 10% of historical totals,
but not in the lowest 5%
Severe deficiency
- rainfalls in the lowest 5% of historical totals
Lowest on record
- lowest since at least 1900 when the data analysed begin
Very much below average
- rainfalls in the lowest 10% of historical totals
Below average
- rainfalls in the lowest 30% of historical totals,
but not in the lowest 10%
Average
- rainfalls in the middle 40% of historical totals
Above average
- rainfalls in the highest 30% of historical totals,
but not in the highest 10%
Very much above average
- rainfalls in the highest 10% of historical totals
For more information regarding this rainfall
deficiencies statement, please contact the following
climate meteorologists in the National Climate Centre:
Lynette Bettio on (03) 9669 4165
David Jones on (03) 9669 4085
Robyn Gardiner on (03) 9669 4671
External Sites Relating to Drought
The Bureau of Meteorology does not make formal drought declarations
as these are done by either the relevant State Governments or by the
Australian Government. The Australian Government Program is called
Exceptional Circumstances
and it is administered by the Federal Department of Agriculture,
Fisheries and Forestry (DAFF). General information about Australian
Government drought assistance is available at
http://www.daff.gov.au/droughtassist.
|
