“2011 was another wet year for Australia, with data collected by the Bureau of Meteorology showing that the Australian mean rainfall total for 2011 was 699 mm (234 mm above the long-term average of 465 mm), placing the year at the third-wettest since comparable records began in 1900. Back-to-back La Niña events led to a two-year rainfall total of 1402 mm which is the second-highest total on record behind 1407 mm in 1973-74.
“The 2010-11 La Niña, one of the strongest on record, continued to dominate climate patterns during the first part of 2011 before decaying in autumn. A second La Niña developed in spring 2011 and, although weaker than the first event, was associated with rainfall significantly above average across much of the country. It is likely that a record warm eastern Indian Ocean also contributed to above average rainfall in 2011.
“From January to March, rainfall was generally very much above average in most areas, and April was rather wet over the north of Western Australia and the Northern Territory. Falls greater than 300 mm across much of the tropical north led to the wettest March on record for Australia as a whole, with average rainfall of 149 mm topping the previous 1989 record by 23 mm. The period from May to September (when La Niña had receded) saw rainfall below average for most of the country. October was very wet in the western half of the country, with Western Australia experiencing its third-wettest October on record. November rainfall was above average for most of the country, while December was wet for the southwest and parts of Queensland. For the year as a whole, the majority of Australia received above average rainfall; the only regions with below-average rain were patches of southwest Western Australia, western Tasmania and pockets of New South Wales and southeast Queensland.
“The Australian area-averaged mean temperature in 2011 was 0.14 °C below the 1961 to 1990 average of 21.81 °C. This was the first time since 2001 (also a wet, La Niña year) that Australia’s mean annual temperature was below the 1961-90 average. Even though, when taken over the whole country, the mean temperature was below average, the southern half of Australia was warmer than usual.
“In 2011, maximum temperatures averaged 0.25 °C below normal across the country, while minima averaged 0.03 °C below normal. Contrasting this, the global mean temperature in 2011 was the highest for any year which began with a La Niña. Australia was one of the few places on the globe to experience cooler than average temperatures in 2011.
Despite the slightly cooler conditions in Australia in 2011, the country’s 10-year average continues to demonstrate the rising trend in temperatures, with 2002-2011 likely to rank in the top two warmest 10-year periods on record for Australia, at 0.52 °C above the long-term average…
Read more at the Australian Bureau of Meteorology website:
http://www.bom.gov.au/announcements/media_releases/climate/change/20120104.shtml
Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.