Australia, the driest inhabited continent, is prone to natural disasters and wild fluctuations in weather conditions – from floods and droughts, to heat waves and bushfires.
Now, two new studies from Flinders University on long-term hydroclimatic models provide new insight into the causes of the high climate variability of the island continent that affect extremely wet or dry weather and other conditions vital to the island continent. water supply, agriculture, environment and the future of the country. .
For the first time, researchers at the National Groundwater Research and Training Center (NCGRT) in Flinders have revealed a wetting-drying phenomenon by vegetation between eastern and western Australia.
The swing phenomenon covered in a new article in The future of the Earth is characterized by the fact that eastern Australia gains water, while western Australia loses water, and vice versa is reset by high humidity induced by La Niña to l continent-wide.
“The swing phase appears to depend on the vegetation cover anomaly before the strong La Niña event, and can be explained by the subsequent interactions of vegetation and soil moisture,” says lead researcher Dr Huade Guan , associate professor in hydrology.
“This discovery provides society with a valuable benchmark for managing forest, water and disaster risk following an upcoming continent-wide heavy wetting induced by La Niña in Australia,” says the co-author, professor at Flinders University, Okke Batalaan.
Precipitation on land comes mainly from evaporation in the oceans. The variation in sea surface temperature – in the tropical Pacific at the rate of the El Nino-Austral oscillation, and in the northern Indian Ocean represented by the Indian Ocean dipole – provides an advance of several months to predict overall drought or wet conditions in Australia.
In another long NCGRT study spanning more than a decade, Flinders researchers assessed the impacts of sea surface temperature variations in southern hemisphere oceans on precipitation in South Australia. They found a seven-year lead-ocean-atmosphere oscillation for precipitation – which could help prepare South Australia for future extreme weather conditions, the Frontiers in Earth Sciences the paper says.
This long-standing study, which began as a postgraduate project (by Dr CP Rofe in 2009), revealed a seven-year delayed precipitation teleconnection with a large-scale ocean-atmosphere oscillation index known as the name of Southern Annular Mode, or Antarctic Oscillation, ”says Associate Professor Guan.
“We filled the teleconnect with a 27-season lag correlation between sea surface temperature off South Australia and the annual southern mode, and a two-season lag correlation between precipitation in Africa. south and sea surface temperature. “
Other co-authors, Dr Wenju Cai (alumnus of CSIRO and Flinders) and former visiting scholars, Dr Lingli Fan and Dr Jianjun Xu (Guangdong Ocean University), confirmed this dominant oceanic teleconnection between 1979 -1998.
“By focusing on this period, we were able to delineate an ocean pathway showing how the seawater temperature anomaly associated with the annual southern mode spread from the southern Pacific Ocean to the southern seas. Australia in about 27 seasons.
“This propagation of sea temperature anomaly only existed in 1979-1998 when the Pacific Ocean was at a certain stage, known as the positive phase of the Interdecadal Pacific Oscillation (IPO). “
With this teleconnection, the team was able to “do a retrospective analysis” of the 1988 and 1999 droughts in South Africa unambiguously with a seven-year time frame, Associate Professor Guan said, adding that the next positive phase of l The IPO will further test this theory to support water and agricultural resources. planning in South Australia.
the The future of the Earth The study confirmed four consecutive periods of wetting and drying of the swings between eastern and western Australia over the past five decades, based on analyzes of terrestrial water storage derived from the satellite. GRACE and extended datasets by co-author and Flinders PhD student Ms. Ajiao Chen.
“These findings support the idea of better rainwater harvesting and other environmental measures to prepare for a drying out phase – and more disaster risk and adaptive land management following a strong continent-wide La Niña-induced humidity in Australia.
“Reducing vegetation cover immediately after the wetting episode could reduce the risk of heat waves and bush fires in the last dry phase,” say the researchers.