THE CLIMATE KELPIE BLOG: Another dry monsoon prompts research into changing summer rainfall patterns

Posted by BCG on 12th February 2020

Summer cropping and other farming businesses that rely on summer rainfall have been left pondering the return of once-reliable wet-season storms after several extremely hot and dry monsoon seasons throughout the mid-latitudes.

The Cotton Research and Development Corporation, through its participation with the Managing Climate Variability (MCV) program has been instrumental in the design and commissioning of a CSIRO study to investigate what’s changed in recent years and what’s driving summer-season rainfall in the sub-tropics.

A new study aims to better understand the leading influences of the monsoon season across northern Australia. Photo: Janet Dampney.

Missing monsoon

CottonInfo Climate Technical Lead, Jon Welsh says many farming and livestock businesses are genuinely concerned and eager to understand the science behind warm-season rainfall so they can evaluate risk and adjust their farm management accordingly.

“Generations of landholders have recounted days of strong easterly winds moving to a northerly direction followed by once-consistent storm rains in summer. But these just haven’t occurred with any frequency in the last seven years.” Mr Welsh said.

Not only does the lack of in-crop rain impact on summer cropping, but broad-acre winter forage and cereal crops rely heavily on stored soil moisture collected during the fallow period to make it through the spring.

“After several disappointing summers, we are really looking for a decent monsoon season to recharge the soil moisture profile and re-fill water storages,” says Mr Welsh.

What drives summer rain?

“From a technical viewpoint, the major climate drivers such as El Niño-Southern Oscillation and Indian Ocean Dipole often take a back seat in the monsoon. To date, the research community have attributed the success or failure of the monsoon season to the impact of ’local factors’ such as sea surface temperatures and upper air disturbances – making this a grey area,” Mr Welsh said.

“There are also multi-year cycles from Interdecadal Pacific Oscillation. Recent analysis by the Queensland Government seems to group summer seasons into alternating wetter or drier cycles over five to seven years, so it would be good to understand how the cycle changes from wet to dry”

The CSIRO study aims to shed some light on the leading influences of the monsoon season through the northern Murray Darling Basin and central and northern wheat belt in Western Australia. Led by CSIRO oceanographers and climate researcher’s, Dr Jaci Brown and Dr Katharina Waha, the study reviews the current science to look for any recent changes in the long-term trends.

AgEcon and Cotton industry researchers Jon Welsh and Janine Powell discuss the climate with Auscott’s Bill Back. Photo: Melanie Jensen.

“Our aim is to separate what is natural variability versus potential trends in our climate – which is challenging over specific regions and shorter timescales,” says Mr Welsh.

“We hope to refresh and build on previous findings, as well as uncover reasons for recent changes in our summer climate, which ultimately impact on many businesses in highly productive temperate agricultural areas.”

The findings from the study will be presented at the Climate Research Strategy for Primary Industries’ (CRSPI) Climate and Carbon in Agriculture Conference at the end of March.

This research has been commissioned by the Managing Climate Variability (MCV) program – Australia’s longest running collaborative research partnership. Members include the Grains Research and Development Corporation, the Cotton Research and Development Corporation, Meat and Livestock Australia, AgriFutures Australia, Sugar Research Australia and the Birchip Cropping Group.

Contact

Jon Welsh, CottonInfo Climate Technical lead, Contact: 0458 215 335 jon@agecon.com.au

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