Tuesday, January 4, 2011

Annual Australian Climate Statement 2010

Bureau of Meteorology

Issued 5th January 2011
2010 La Niña event brings Australia's third-wettest year on record.
  • La Niña brings heavy rain, eases drought and causes widespread flooding
  • Prolonged dry conditions continue in southwest Western Australia
  • Australia's coolest year since 2001
  • Australia's warmest 10 years on record


Data collected by the Bureau of Meteorology show that the Australian mean rainfall total for 2010 was 690 mm, well above the long-term average of 465 mm. As a result, 2010 was Australia's wettest year since 2000 and the third-wettest year on record (records commence in 1900). The only month to record a national monthly total below the long term average during 2010 was June. This means that 11 months of the year experienced above average rainfall, an occurrence observed only once previously, in 1973.
2010 began with El Niño conditions in the Pacific followed by a rapid transition into La Niña during autumn. From January to May rainfall was generally above average in most areas except the western half of Western Australia and southern Tasmania. By July, La Niña conditions were well established and most areas of Australia experienced very much above average rainfall. The second half of the year (July to December) was the wettest on record for Australia.
However, not all areas were very wet during 2010. Southwest Western Australia had its driest year on record, and Tasmania had near to average rainfall for the year; the result of a dry first six months followed by a relatively wet second six months.
Mean temperatures in 2010 were cooler than those for the previous eight years, with an average of 22.0°C+0.19 °C above the 1961 to 1990[1] average of 21.81 °CDespite 2010 being cooler than recent years, the decade ending 2010 is now the hottest decade on record for Australia with an anomaly of +0.52 °C. This underscores that the warming of Australia's climate continues, even though individual years may be cooler than other years.

Very wet through the north and east

Rainfall was above average across most of the country, with record rainfall reported in many areas. Unusually heavy falls were experienced in Queensland, New South Wales, the Northern Territory and South Australia. Based on preliminary numbers, 2010 was the wettest year on record for Queensland. The Northern Territory, New South Wales and South Australia experienced their 3rd wettest year on record, and Victoria experienced its 5th wettest year on record.

Drought eases in the east but continues in the southwest

For some parts of the southeast 2010 was the first calendar year since 1996 to see above average rainfall. The heavy rainfall in 2010 marked a dramatic reversal of dry conditions across Queensland, New South Wales, Victoria and South Australia. Significantly, the Murray Darling Basin recorded its wettest year on record, ending a record sequence of below average rainfall years extending back to 2001. This rainfall led to a dramatic recovery in water storages across the Murray-Darling Darling Basin from 26% at the start of 2010 to 80% at the start of 2011.
From the point of view of surface water, soil moisture and annual rainfall totals; the "long dry" which commenced in late 1996 in the far southeast of mainland Australia and late 2001 across much of the Murray-Darling Basin has effectively ended.
In contrast to the rest of the continent, the southwest of Western Australia experienced a very dry year, continuing the long drying trend which extends back to the late 1960s. For the southwest region as a whole, the 2010 rainfall total was a record low 392 mm, well below the previous low of 439 mmin 1940. Rainfall in the cropping season (April to October) in southwest Western Australia also set a record with just 310 mm falling; the previous low was 348 mm in 1914.

Wettest on record "dry season" in the north

For the period from May to October, considered to be northern Australia's dry season, conditions were abnormally wet. Northern Australia had its wettest dry season on record, measuring an average of190 mm of rainfall, compared with the previous record of 176 mm in 1978. June was the only month to see the widespread dry conditions that are typical of the season. September was a particularly notable month for rainfall, coming in as the wettest on record for northern Australia with an average of 51 mm, well above the previous record of 33 mm set in 1906.

Big wet results in coolest year since 2001 but nonetheless the warmest decade on record

Overall, Australia's annual mean temperature for 2010 was 22.00 °C+0.19 °C above the 1961 to 1990 average of 21.81 °C. This ranks as the nation's 31st-warmest year since standard records began in 1910. It has now been a record nine years since Australia experienced a below-average year and the past ten years (2001 to 2010) were the warmest decade on record for Australia.
Temperatures were generally cooler than average in the interior of the continent where rainfall was particularly high. By contrast, the north and west were much warmer than normal. Warmer than normal sea surface temperatures in the Coral Sea contributed to the warm temperatures in the Cape York Peninsula. Tasmania was also warmer than normal.
Australia recorded its 8th warmest year on record for minimum temperatures (with an anomaly of+0.59 °C), while maximum temperatures were below normal with an anomaly of −0.21 °C. The tropics were particularly warm during the July to October period, with widespread areas in the Top End of the Northern Territory, the Gulf of Carpentaria and the Cape York Peninsula having their warmest on record mean temperatures. In marked contrast with 2009, days with extreme high temperatures were scarce. However 2010 saw regular, very high overnight minimum temperatures in the northern tropics during winter, including an Australian July record of 26.9 °C at Cape Don in the Northern Territory.

Flooding and storms

As can occur during significant La Niña events, there were numerous significant floods in Australia during 2010, especially in the eastern states. The most widespread and damaging floods of the year occurred across Queensland in the final week of 2010 (and continuing into early 2011). Floodwaters were fed by heavy rain over the Christmas period falling over areas already saturated by persistent above-average rainfall during the preceding months. The most severe impacts were in central Queensland and in the state's southern inland regions. Thousands of properties were inundated in Emerald, Bundaberg, Rockhampton and many smaller centres, while the communities of Theodore and Condamine were evacuated. Numerous rivers throughout the region reached record levels. Damage to property and infrastructure, as well as the economic cost from crop losses and disruptions to mining, is expected to run to several billion dollars.
An earlier major flood event in late February and early March affected central Australia, Queensland and far northern New South Wales. A monsoon low located over the Northern Territory moved southwards and then eastwards into southern Queensland, and then into northern New South Wales. This system produced heavy rainfall in its path resulting in widespread flooding. Major flooding occurred in most of the catchments in southern inland Queensland, and some of these areas had their highest flood levels on record. This event also brought minor flooding to the southern Northern Territory, and as the Queensland waters moved downstream, significant flooding occurred in northwest New South Wales, with some areas remaining affected by floodwaters well into April. It also combined with earlier regular rains in inland Queensland to contribute to a significant filling of Lake Eyre.
Many other floods occurred during the year. Significant flooding occurred across inland New South Wales in December, particularly in the Murrumbidgee Catchment around Queanbeyan and Wagga Wagga, and the Lachlan Catchment around Eugowra (which was flooded three times during the month). Major floods also occurred in northern Victoria and the New South Wales Riverina region in early September; and the Gascoyne River around and upstream of Carnarvon in mid-December.
Two significant and highly damaging thunderstorm events producing large hailstones occurred during March 2010, with losses from each event estimated by the Insurance Council of Australia to exceed $1 billion. The first occurred in Melbourne on 6 March, with the heaviest falls coming in less than 30 minutes, resulting in flash flooding in the inner city. Hail up to 5 cm in diameter fell across a large swathe of Melbourne with widespread damage to cars and houses. A 10 cm hailstone was measured in the suburb of Ferntree Gully, in Melbourne's east, twice the diameter of the previous largest stone on record for Melbourne.
The second thunderstorm event occurred in Perth on the afternoon of 22 March. This thunderstorm produced heavy rain, severe winds and the largest hail stones on record for Perth. The largest hail from this storm occurred in the northwestern suburb of Wembley, where a 6 cm hailstone was reported.

Sea surface temperatures near Australia

Based on preliminary data (to November 30), sea surface temperatures in the Australian region during 2010 were +0.54 °C above the 1961 to 1990 average. This is the warmest value on record for the Australian region. Individual high monthly sea surface temperature records were also set during 2010 in March, April, June, September, October and November. Along with favourable hemispheric circulation associated with the 2010 La Niña, very warm sea surface temperatures contributed to the record rainfall and very high humidity across eastern Australia during winter and spring. The most recent decade (2001−2010) was also the warmest decade on record for sea surface temperatures following the pattern observed over land.

Globally 2010 is likely to be one of the warmest years on record

The past year has been very warm globally, though it remains too early to determine if the year will be the warmest or second warmest on record.
On 3 December the World Meteorological Organization (WMO) declared that year 2010 is almost certain to rank in the top three warmest years since the beginning of instrumental climate records in 1850. The global combined sea surface and land surface air temperature for 2010 (January−October) is currently estimated at +0.55 °C ± 0.11 °C above the 1961 to 1990 annual average of 14.0 °C.
A cooler-than-average global mean temperature has not been recorded since 1985 (for the last 25 years). The past 10 years have been the globe's hottest on record with an anomaly of +0.46 °C. Increasing global mean temperatures derived from instrumental measurements are consistent with other independent indicators of climate change, such as reductions in ice and snow cover, and rises in global sea levels.

Accessing Australia's climate change datasets

The Bureau of Meteorology is responsible for collecting, managing and safeguarding Australia's climate archive. Several high-quality datasets have been developed from this archive to identify, monitor and attribute changes in the Australian climate. Extensive rehabilitation work has been undertaken on these data to ensure they have not been compromised by changes in site location, urbanisation, exposure or instrumentation over time. The high-quality data can be accessed at:http://www.bom.gov.au/climate/change/hqsites/
Please note that heavy rainfall over the Christmas-New Year period, with severe flooding in Queensland, has affected the availability of rainfall data for northeast Australia. As these data are processed in the next few months the final rainfall figures are expected to change.

No comments: