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Positive IOD influencing Australian wine production

Ben Domensino, Tuesday September 24, 2019 - 15:59 AEST

Australia is one of the largest wine producing countries in the world. But our notoriously diverse weather and broad-scale climate drivers can affect our ability to produce wine each year.

Australia produces 1.3 billion litres of wine annually, making us the 6th largest producer and 5th largest exporter of wine in the world.

According to the latest figures published by Wine Australia, our country's wine sector contributes $40 billion to the national economy each year and supports more than 170,000 jobs across the country.

However, Australia is a land of extremes and no two seasons are the same. So, how do variations in the weather affect our country's ability to produce wine?

"When it's hot and dry wine grapes tend to grow faster," says Chelsea Javis, a research fellow at the University of Southern Queensland.

"If these warmer temperatures happen in the Spring-time months it can really accelerate development, which means the grapes end up being harvested earlier in the season."

The main wine-producing regions in Australia are scattered across the nation's southern and eastern states. The weather in these parts of the country can be influenced strongly by broad scale climate drivers such as El Nino, La Nina and the Indian Ocean Dipole (IOD).

This year, the Pacific Ocean is in a neutral phase, meaning that neither El Nino or La Nina are occurring. However, sea surface temperatures in the Indian Ocean are currently in a pattern that's likely to produce warmer and drier than usual weather in large parts of Australia during the coming months.

This pattern is called a positive IOD, which occurs when cooler-than-usual water develops to the northwest of Australia and unusually warm water forms off the east coast of Africa near the equator. Positive IOD events usually reduce the amount of moisture travelling over Australia from the west, which typically causes below average rain and above average temperatures over parts of our country's wine growing-regions during winter and spring.

Earlier this week, the IOD index reached a value of +1.5ºC, which is well above the +0.4C threshold used by the Bureau of Meteorology to identify positive IOD events. According to Dr Andrew Watkins, Head of Long Range Forecasts at the Bureau of Meteorology, this is the highest weekly IOD value in records dating back to 2001.

Image: Weekly IOD index values. Source: Bureau of Meteorology.

This climate driver could play a big role in Australia's ability to produce wine during 2019.

Wine Australia's National Vintage Report for 2019 estimates that the overall production of wine grapes will drop by just 3% this year, compared to the previous year. Overall production in 2019 is expected to be close to the long-term average.

Unsurprisingly, the production of cool-climate grapes is expected to decline more than warm-climate grapes, in response to the recent spate of unusually warm and dry weather.

According to the Bureau of Meteorology, southern Australia experienced above average temperatures during the first eight months of 2019. For the country as a whole, it has been the 2nd warmest year to date on record.

Image: Monthly mean temperatures for 2019 to date.

Rainfall has also been below the long-term average during each month so far this year. Some areas of central and eastern Australia experienced their driest year-to-date on record based on rainfall between January and August.

With the trend of warmer and drier than usual weather expected to continue across much of the country during the coming months, local growers are already taking steps to ensure that 2019 will still produce plenty of good quality wine to go around.

"Just because it's hot and dry doesn't mean that the wine is going to be bad" said Ms Javis.

"Some of the best vintages happen when it's hot and dry because the winemakers can actually control the hot dry vintage a lot more than they can control a cold, wet one."

"So I would definitely say that there's likely to be some really great wines coming out this year," she concluded.

- Weatherzone

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