Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Understanding autumn rain decline in SE Australia

27.05.2008
Fluctuations in sea-surface temperatures to the north of Australia and changes in atmospheric circulation patterns over the sub-tropical Indian Ocean have been identified as key factors leading to declining rainfalls in south-eastern Australia since 1950.

According to a report from a CSIRO Wealth From Oceans Flagship study – published this week in the science journal Geophysical Research Letters – since 1950 Victoria has suffered a 40 per cent decline in autumn rainfall (March to May) compared to the average recorded between 1961–90.

The report’s authors, CSIRO’s Dr Wenju Cai and Tim Cowan, say that the decline has been most prominent in May, which accounts for about half of the total seasonal reduction.

“Through April and May, large increases in sea surface temperatures in the region are usually associated with a transition from an El Niño to a La Niña event” Dr Wenju Cai, CSIRO Marine and Atmospheric Research The identified causes show imprints of climate change influences, in part through a reduction in the number of La Niña events, and in part through changing weather systems originating from the subtropical Indian Ocean that are conducive to late autumn rainfall across Victoria.

The researchers found that since 1950 the spatially alternating high and low pressure systems (called pressure wave-trains) conducive to rainfall over southern Victoria in May have been weakening, leading to rising sea level atmospheric pressure over south-east Australia.

“This weakening is reinforced by a warming of the Indian Ocean, which is at least in part due to global warming,” Dr Cai says. “This suggests that a component of climate change is active in southern Victoria receiving less rainfall.”

Influences from the Indian Ocean sector occur in conjunction with those from the Indonesian Throughflow region, to the north of Australia. Dr Cai says higher sea surface temperatures in the Throughflow region are conducive to rainfall in central and northern south-east Australia, through the familiar tropical northwest cloud bands, which deliver rainfall to the region.

“Through April and May, large increases in sea surface temperatures in the region are usually associated with a transition from an El Niño to a La Niña event, as part of cycle of the El Niño-Southern Oscillation,” he says.

Mr Cowan says that in recent decades, there have been more El Niño events than La Niñas. As the system spends more time in an El Niño phase, and less time transitioning to a La Niña, south-east Australia receives less rainfall. “This El Niño-like behaviour pattern of the Pacific system is also consistent with what is expected from climate change, as recent studies have shown,” he says. Victoria is not alone among states experiencing rainfall declines. During the past 50 years there has been a decreasing trend in rainfall over much of Australia. In south-west Western Australia the trend is strongest in winter; and in southern Queensland strongest in summer.

National Research Flagships

CSIRO initiated the National Research Flagships to provide science-based solutions in response to Australia’s major research challenges and opportunities. The nine Flagships form multidisciplinary teams with industry and the research community to deliver impact and benefits for Australia.

Craig Macaulay | EurekAlert!
Further information:
http://www.csiro.au
http://www.csiro.au/news/UnderstandingDeclineAutumnRain.html

More articles from Earth Sciences:

nachricht Six-decade-old space mystery solved with shoebox-sized satellite called a CubeSat
15.12.2017 | National Science Foundation

nachricht NSF-funded researchers find that ice sheet is dynamic and has repeatedly grown and shrunk
15.12.2017 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>