A NEW climate tool is changing farming practices in South-West WA and providing researchers with a different approach to tackling Australia’s 30 year drought.

An example of rainfall collected in the South-West / Image - Courtesy Willem van Aken, CSIRO

CSIRO statistician Dr Yun Li and climate physicists Professors Jianping Li and Juan Feng from the Chinese Academy of Sciences collected and analysed rainfall data from Australia and China to create the South-West Australian Circulation Index (SWACI).

The SWACI measures the atmospheric circulation, or spatially alternating high and low pressure systems, over the Indian Ocean.
 
The index has indicated dry conditions in South-West WA are caused by a change in early autumn seasonal winds that produce a high pressure system to deliver weaker westerly and northerly winds.

“The SWAC index explains not only a large portion of the inter-annual variability of SWWA rainfall in both early and late winter but also the long term drying trend over SWWA in early winter,” Dr Li says.

“Using this new index we have found that the South-West Australian Circulation is becoming weaker early in the winter wet season (May to July) causing the drier conditions observed in South-West WA.

“The climate of South-West Australia bears a strong seasonality in the annual cycle and exhibits a monsoon-like atmospheric circulation.”

The WA Wheatbelt is one the hardest hit regions, sustaining a period of low rainfall since the 1970s.

CSIRO climate scientists are working with the Department of Agriculture and Food WA to investigate the predictability of the SWACI with an aim to see if they can improve their skills in forecasting seasonal rainfall and crop growth potential in South-West WA.

Dr Senthold Asseng is the Principal Research Scientist in the CSIRO Climate Adaptation Flagship and the CSIRO Agriculture Sustainability Flagship. He says the SWACI can help understand what drives the seasonal variability to develop sustainable atmosphere-crop-soil systems.

“We can use this information for seasonal forecasting systems which will help farmers to increase returns in the good seasons (by applying more fertiliser for potential higher yields in wet seasons) and reduce/save input costs in dry, low yielding seasons.

“Reduced rainfall will reduce yields if the decline will be in autumn and delays the sowing or in spring increasing terminal water deficit stress during grain filling.

As the degree in rainfall decline is uncertain, the positive side for farmers is the likelihood CO2 in the atmosphere will increase and improve water use efficiency and growth of crops.

Dr Asseng says the research will focus on improving the understanding of our atmosphere crop soil systems, managing climate variability, discovering species which best adapt to the changes, potential for new farming systems and understanding potential thresholds and tipping points when systems might change significantly.

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