Effects of the El Niño–Southern Oscillation in Australia
Effects of the
Through
Climate Modelling
The Bureau of Meteorology is Australia’s governing body for monitoring climate drivers and model data. All climate models developed at leading international climate agencies are utilised by the Bureau for climate driver monitoring and data sourcing. All models use an ensemble method, where several forecasts are run at the same time using slightly different initial conditions. While all models use ensemble techniques, the number of ensembles differs for each model.[9] The Climate Model Summary is updated on the 12th of each month (or the next working day following the 12th) when model data becomes available. Data for the Bureau's model, ACCESS–S, is updated fortnightly along with several other models that also provide more frequent updates during the month.[9]
Impacts
El Niño
El Niño episodes are defined as continuous warming of the central and eastern tropical Pacific Ocean, thus resulting in a decrease in the strength of the Pacific trade winds, and a reduction in rainfall over eastern and northern Australia, particularly in winter and spring. An El Niño event typically begins in autumn and fully forms during winter and spring, but would then would start to dissipate by summer, with the event usually concluding in the autumn of the next year. Snow depth during El Niño years is generally lower in Australia's alpine regions.[10]
Furthermore, El Niño years generally experience warmer-than-average temperatures with hotter daily
El Niño's effect on Australian rainfall decreases after November, particularly in the southeast, and therefore a pronounced difference between the rainfall patterns of early and late summer would exist. Nonetheless, Cape York and northwest Tasmania would have moderately dry conditions. Some areas on the Queensland/New South Wales border exhibit a small inclination for wetter conditions. There is also a reasonably stronger propensity for wetter than average conditions in the southeast of Western Australia.[11]
La Niña
La Niña episodes are defined as uninterrupted cooling of the central and eastern tropical Pacific Ocean, thus resulting in an increase in the strength of the Pacific
La Niña is characterised by increased rainfall and cloud cover, especially across the east and north that continue into the warm months (unlike El Niño events); the average December–March precipitation is 20% higher than the long-term average, particularly in the east coast. Snow depth and snow cover is increased in the southeast during winter. There are also cooler daytime temperatures south of the tropics (especially during the second half of the year) and fewer extreme highs, and warmer overnight temperatures in the tropics. There is less risk of
SOI and IOD
The Southern Oscillation is the atmospheric component of El Niño. This component is an oscillation in surface
In several recent studies, it is shown that the Indian Ocean Dipole (IOD) has a much more significant effect on the rainfall patterns in south-east Australia than the El Niño-Southern Oscillation (ENSO) in the Pacific Ocean.[16][17][18] It is further demonstrated that IOD-ENSO interaction is a key for the generation of Super El Ninos.[19] When an El Niño occurs with a positive IOD, the two events can strengthen their dry impact. Similarly, when La Niña coexists with a negative IOD, the chance of above-average winter–spring rainfall generally increases.[20]
History
Paleoclimate record
During the
1880s–1920s
1885 to 1898 were mostly La Niña years, being generally wet, though less so than in the period since 1968. The only noticeably dry years in this era were 1888 and 1897. Although some coral core data[22] suggest that 1887 and 1890 were the wettest years across the continent since settlement.[23] In New South Wales and Queensland, however, the years 1886–1887 and 1889–1894 were indeed exceptionally wet La Niña years, and February 1893 saw the disastrous 1893 Brisbane flood.[24]
1903–04 were La Niña years, which followed the
1920s–1960s
The period from 1922 to 1937 was particularly dry with most years having a positive El Niño phase, with only 1930 having Australia-wide rainfall above the long-term mean and the Australia-wide average rainfall for these seventeen years being 15 to 20 percent below that for other periods since 1885. This dry period is attributed in some sources to a weakening of the Southern Oscillation[26] and in others to reduced sea surface temperatures.[27] During World War II, eastern Australia suffered El Niño conditions which lasted from 1937 through to 1947 with little relief, despite a few weak and relatively dry La Niña years in between (1938–39 and 1942–43).[28]
1949–51 were La Niña years, which had significant rain events in central New South Wales and most of Queensland: Dubbo's 1950 rainfall of 1,329 mm (52.3 in) can be estimated to have a return period of between 350 and 400 years, whilst Lake Eyre filled for the first time in thirty years. 1954–57 were also intense La Niña years. In contrast, 1951–52, 1961 and 1965 were very dry, with complete monsoon failure in 1951–52 and extreme drought in the interior during 1961 and 1965. 1964–69 were moderate La Niña years. Conditions had been dry over the centre of the continent since 1957 but spread elsewhere during the summer of 1964–65. The El Niño conditions from 1965–70 contributed to the 1967 Tasmanian fires.[29]
1970s–1990s
The wettest periods in this century have been from 1973 to 1976, peaking in 1974, all La Niña years. The
Most of the 1990's were characterised by El Niño events; Beginning in the second half of 1991, a very severe drought occurred throughout
2000s
The 35 months from May 1998 to March 2001 can be considered a long La Niña phase, although much of eastern Australia experienced a dry 2001.[40] 2002 was one of Australia's driest and warmest years on record, with 'remarkably widespread' dry conditions, particularly in the eastern half of the country which was again affected by El Niño conditions. It was, at the time, Australia's fourth-driest year since 1900.[41] The El Niño weather pattern broke down by 2004, but occasional strong rainfall in 2003 and 2004 failed to alleviate the cumulative effect of persistently low rainfall in south-eastern Australia.[42][43]
South-east Australia experienced its second-driest year on record in 2006, an El Niño year, particularly affecting the major agricultural region of the Murray–Darling basin.[44] In early 2007, forecasters believed that the El Niño effect that had been driving the drought since 2006 had ended, though the Murray–Darling Basin experienced their seventh consecutive year of below-average rain.[45][46] Wildfires such as the 2003 Canberra bushfires in January and the worst bushfires in Australian history, which occurred on Black Saturday in February 2009, were intensified when combined with a positive Indian Ocean Dipole (IOD) event.[47]
Although 2007 to early 2009 were moderate La Niña years, hot and dry conditions still prevailed in parts of south-eastern Australia, with occasional heavy rainfall failing to break the continuing drought.[48] The effects of the drought were exacerbated by Australia's (then) second-hottest year on record in 2009, with record-breaking heatwaves in January, February, and the second half of the year, when El Niño conditions returned, which also brought a powerful dust storm in the east.[49]
2010s
According to the
El Niño conditions developed in mid-2013 through much of western Queensland.[53] Although these began easing for western Queensland in early 2014, drought began to develop further east, along the coastal fringe and into the ranges of southeast Queensland and northeast New South Wales.[54] Warm and dry conditions continued into 2015 in the east, particularly in Queensland where the monsoon rains were delayed.[55] The 2013 New South Wales bushfires occurred in a neutral ENSO year, as not all major fires occur in El Niño years.[56]
By the start of spring in 2015, the Indian Ocean had started to help the El Niño, which resulted in Australia's third-driest spring on record and limited growth at the end of cropping season. The combination of heat and low rainfall brought a very early start to the 2015–16 Australian bushfire season, with over 125 fires burning in Victoria and Tasmania during October.[57] During the 2014–2016 El Niño event, the 2015–16 Australian region cyclone season was the least active since reliable records started during 1950s.[58][59]
Mild La Niña conditions were present from April to November 2016. Moderate, albeit brief, La Niña conditions returned in the summer of 2017–18.[60] Despite a few and short-lived La Niña outbursts, 2017–19 mostly consisted of El Niño conditions and had caused drier than average conditions for much of inland Queensland, most of New South Wales, eastern and central Victoria, and all of Tasmania.[61] In 2018, rainfall for the year was very low over the southeastern quarter of the Australian mainland.[62] Exacerbating the effects of diminished rainfall during the 2018 El Niño year were a record-breaking run of above-average monthly temperatures, with the first half of 2019 being on an El Niño alert.[63]
2020s–present
Although the unusually powerful
November 2021 was one of the wettest on record across some areas in eastern and northern Australia, after a La Niña was officially declared for the 2021–22 summer, making it the first back-to-back La Niña event since 2010–12.[68] Moreover, the summer of 2021–22 in Sydney was the wettest in 30 years due to the persisting La Niña conditions.[69] From late February to early March 2022, southeastern Queensland and northeastern New South Wales experienced significant rainfalls and flooding, which marked the phase of two years of wet La Niña summers in eastern Australia.[70][71][72]
After the floods in July 2022 in New South Wales, La Niña was declared once again for spring as higher than above average rainfall was recorded in October in New South Wales, making it the third La Niña event in a row.[73][74] In March 2023, La Niña was officially declared over in Australia, with sea surface temperatures returning to normal or neutral.[75] In July 2023, the World Meteorological Organization declared that El Niño has developed in the tropical Pacific for the first time in 7 years.[76] In September 2023, the Bureau of Meteorology formally declared an El Niño weather event, for the first time in 8 years, after hot and dry conditions prevailed over south-east Australia during spring.[77]
See also
- Climate of Australia
- Climate change in Australia
- Drought in Australia
- Floods in Australia
- Bushfires in Australia
References
- Sydney Morning Herald, December 29, 2020.
- ^ La Niña In Australia Bureau of Meteorology. www.bom.gov.au
- ^ El Niño in Australia Bureau of Meteorology. www.bom.gov.au
- ^ "Climate Driver Update". Bureau of Meteorology. Bureau of Meteorology. 17 September 2023.
- ^ King, Andrew (13 September 2022). "La Niña, 3 years in a row: a climate scientist on what flood-weary Australians can expect this summer". The Conversation.
- ^ What is La Nina and what does it mean for your summer? By Peter Hannam and Laura Chung. The Sydney Morning Herald. November 25, 2021.
- ^ Bureau of Meteorology (Australia). 2002-04-03. Retrieved 2009-12-31.
- ^ Australian Climate Extremes – Fire, BOM. Retrieved 2 May 2007.
- ^ a b "Model Summary". Bureau of Meteorology. Retrieved 26 September 2023.
- ^ "What is La Niña and how does it impact Australia?". Bureau of Meteorology. www.bom.gov.au. Australian Government. Retrieved 25 September 2020.
- ^ Climate Driver Update www.bom.gov.au. Retrieved 27 November 2021.
- S2CID 55572677.
- ^ Fewer frosts. Bureau of Meteorology.
- ISSN 1944-8007.
- .
- .
- S2CID 17013509.
- doi:10.1038/NGEO760.
- S2CID 128595874.
- ^ Indian Ocean influences on Australian climate - When the Indian and Pacific oceans work together The Bureau of Meteorology. Retrieved 2 December 2021.
- S2CID 4303100.
- ^ "Commentary on rainfall probabilities based on phases of the SOI". www.longpaddock.qld.gov.au. Department of Environment and Resource Management. Archived from the original on 1 August 2008. Retrieved 27 February 2008.
{{cite web}}
: CS1 maint: others (link) - doi:10.1002/gdj3.19.
- ^ Foley, J.C.; Droughts in Australia: review of records from earliest years of settlement to 1955; published 1957 by Australian Bureau of Meteorology
- ^ "The 1914–15 drought". Climate Education. Australian Bureau of Meteorology. 1999. Archived from the original on 17 March 2009. Retrieved 13 November 2006.
- ISBN 0-643-05803-6
- ^ "Soils and landscapes near Narrabri and Edgeroi, NSW, with data analysis using fuzzy k-means" (PDF). Archived from the original (PDF) on 2021-08-13. Retrieved 2021-11-24.
- ^ "The World War II droughts 1937–45". Climate Education. Australian Bureau of Meteorology. 1999. Archived from the original on 17 March 2009. Retrieved 13 November 2006.
- ^ "The 1965–68 drought". Climate Education. Australian Bureau of Meteorology. 1999. Archived from the original on 17 March 2009. Retrieved 13 November 2006.
- ^ "Short but sharp – The 1982–83 droughts". Climate Education. Australian Bureau of Meteorology. Archived from the original on 17 March 2009. Retrieved 13 November 2006.
- ISBN 0-9592418-3-3(page 151)
- ^ a b Collie, Gordon (26 August 1995). "Worst drought of century cripples farmers". The Courier-Mail. p. 14.
- ^ Collie, Gordon. Dry tears of despair. The Courier-Mail. p. 29. 22 October 1994.
- The Courier Mailp. 3. 3 June 1995
- ^ Coleman, Matthew (30 August 1995). "Crops worth $50m lost". The Courier-Mail.
- ISBN 0-9592418-3-3.
- The Courier Mail. p. 3.
- ^ Australian Bureau of Statistics (27 February 1998). "1998 Yearbook – Climate Variability and El Nino". www.abs.gov.au. Retrieved 26 January 2017.
- ^ Australian rainfall during El Niño and La Niña events www.bom.gov.au Bureau of Meteorology
- ^ Bureau of Meteorology (3 January 2002). "Annual Australian Climate Summary 2001". www.bom.gov.au. Retrieved 26 January 2017.
- ^ Bureau of Meteorology. "Annual Australian Climate Summary 2002". www.bom.gov.au. Retrieved 26 January 2017.
- ^ Bureau of Meteorology. "Annual Australian Climate Summary 2004". www.bom.gov.au. Retrieved 26 January 2017.
- ^ Bureau of Meteorology. "Annual Australian Climate Statement 2005". www.bom.gov.au. Retrieved 26 January 2017.
- ^ Bureau of Meteorology. "Annual Climate Statement 2006". www.bom.gov.au. Retrieved 26 January 2017.
- ^ Barlow, Karen (22 February 2007). "El Nino declared over". Water. Australian Broadcasting Corporation. Archived from the original on 17 May 2012. Retrieved 23 October 2007.
The Bureau of Meteorology has declared that the El Nino which has made the drought so much worse for the past year or so has passed. A senior climatologist at the Bureau of Meteorology, Grant Beard, says it's time to be optimistic about drought-breaking rains, although the drought is far from over yet.
- ^ Bureau of Meteorology. "Annual Australian Climate Statement 2007". www.bom.gov.au. Retrieved 26 January 2017.
- ^ "Police: Australian fires create 'a holocaust'". CNN. 9 February 2009.
- ^ Australian rainfall during El Niño and La Niña events www.bom.gov.au. Bureau of Meteorology.
- ^ Bureau of Meteorology. "Annual Australian Climate Statement 2009". www.bom.gov.au. Retrieved 26 January 2017.
- ^ "Annual Australian Climate Statement 2011". Bom.gov.au. 4 January 2012. Retrieved 15 April 2012.
- ^ "The 2010–11 La Niña: Australia soaked by one of the strongest events on record". Bureau of Meteorology. Retrieved July 22, 2015.
- PMID 23429502. Retrieved July 22, 2015.
- ^ "Rainfall deficiencies increase in Queensland and northeastern New South Wales". Climate: Drought: Archive. Australian Bureau of Meteorology. 7 August 2014.
- ^ "Rainfall deficiencies increase in Queensland and northeastern New South Wales". Climate: Drought: Archive. Australian Bureau of Meteorology. 7 August 2014.
- ^ "Annual Australian Climate Statement 2015". Australian Bureau of Meteorology. Retrieved 26 January 2017.
- ^ What is Niño and how does it impact Australia? Bureau of Meteorology, issued June 2014. Retrieved 24 November 2021.
- ^ Cook, Alison; Watkins, Andrew B; Trewin, Blair; Ganter, Catherine (May 2016). "El Niño is over, but has left its mark across the world". Australian Bureau of Meteorology. Archived from the original on 1 July 2016.
- ^ Dry and hot in the northern tropics (Report). Australian Bureau of Meteorology. May 2016. Archived from the original on 17 June 2016. Retrieved 10 May 2016.
- ^ 2015–16 southern hemisphere wet-season review (Report). Australian Bureau of Meteorology. 10 May 2016. Archived from the original on 17 June 2016. Retrieved 10 May 2016.
- ^ ENSO Outlook - An alert system for the El Niño–Southern Oscillation Australian Bureau of Meteorology. Retrieved 1 December 2021.
- ^ "Annual Australian Climate Statement 2017". Australian Bureau of Meteorology. Retrieved 29 June 2019.
- ^ "Annual Australian Climate Statement 2018". Australian Bureau of Meteorology. Retrieved 29 June 2019.
- ^ Australia records three years of hotter than average monthly temperatures Sydneys Kiss FM, 5 November 2019.
- ^ "Australia fires: Life during and after the worst bushfires in history". BBC News. 28 April 2020.
- ^ What is the meaning of La Niña and how will the weather event affect Australia’s summer? www.theguardian.com
- ^ La Nina set to be declared: The dangerous change to Australia’s weather by Benedict Brook from News.com.au. November 16, 2021.
- ^ "How NSW's devastating floods stack up against past deluges". www.abc.net.au. 2021-03-25. Retrieved 2021-04-08.
- ^ Eastern and northern Australia told to prepare for wet summer as La Niña develops for the second year in a row by Jack Mahony from Sky News. November 23, 2021,
- ^ Sydney rain smashes summer records as cleanup from deluge continues By Raffaella Ciccarelli from 9news. February 24, 2022.
- ^ Queensland's wet weather continues with more than 400mm of rain falling in three hours, flood warnings issued ABC News Australia. 25 February 2022.
- ^ The wild ways of La Niña As storms batters, the east coast, is this what our future looks like? by Cosmos. 25 February 2022
- ^ Six dead, thousands in Ipswich and Brisbane on alert as wild weather continues to lash Queensland By Ashleigh McMillan and Stuart Layt from The Sydney Morning Herald. February 27, 2022.
- ^ La Niña, 3 years in a row: a climate scientist on what flood-weary Australians can expect this summer By Andrew King from The Conversation. September 13, 2022.
- ^ How La Niña could wipe out stretches of Australia's beaches and dunes with wild weather ABC News. October 8 2022.
- ^ La Niña’s three-year reign across Australia finally ends, promising drier, hotter weather by ABC News Australia. Tom Saunders. 10 March 2023. Retrieved 19 September 2023.
- ^ World Meteorological Organization declares onset of El Niño conditions by WMO. 4 July 2023. Retrieved 19 September 2023.
- ^ Bureau of Meteorology formally declares El Niño weather event, as hot and dry conditions sweep south-east Australia By Tom Williams and Brianna Morris-Grant from ABC News. 19 September 2023.
External links
- ENSO Outlook an alert system for the El Niño–Southern Oscillation by BOM
- El Niño Southern Oscillation (ENSO) by BOM