Photo: Parker Blain / Wine Australia

New weather data: how the 2017–18 viticultural growing conditions compared with long-term averages

Market Bulletin | Issue 144
Photo: Parker Blain / Wine Australia
19 Feb 2019
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According to the Bureau of Meteorology, 2018 was the third hottest year on record for Australia, with an average temperature 1.14 degrees above the long-term average[1]. This is a very broad and general statistic, however, that does not provide much insight into the conditions that prevailed for winegrape growers around Australia.

Newly published viticulturally relevant climate and weather indices, calculated specifically for each GI region[2], enable us to look more closely at how the 2017–18 viticultural growing conditions (heading into vintage 2018) compared with long-term averages.

The 2017–18 season was warmer and drier than average across most of Australia’s winegrowing regions

The numbers confirm that it was a warmer and drier season. The average mean January temperature (MJT) across all Australia’s wine regions was 22.6 degrees – 7 per cent above the recent long-term average[3] and 10 per cent above the historical average[4]. There were only 9 regions where the 2018 MJT was below the average: these were all Western Australian GI regions. Figure 1 shows the comparison between the 2018 MJT and the 2 average periods for selected regions, from the warmest to the coolest.

Figure 1: Mean January temperature (MJT) for selected regions over time

Similarly, annual rainfall in 2017–18 averaged across all GI regions was 635 mm, compared with the recent average (1991–2017) of 699 mm and the historical average (1961–1990) of 739 mm.

Annual rainfall by region was more variable than MJT. Most regions had below average rainfall, but 20 regions had rainfall totals above the recent average, while 10 of those were also above the earlier average. Coonawarra, Peel and Perth Hills exceeded their recent average rainfall by more than 10 per cent (see Figure 2).

Figure 2: Annual rainfall for selected regions over time

How wine regions compare in terms of viticultural weather-related measures

The wettest wine region on average[5] is Hastings River (NSW) with 1319 mm annual rainfall, followed by Tasmania’s northwest coast with 1244 mm and Alpine Valleys (Vic) with 1187 mm. In general, the higher the rainfall, the cooler the MJT and the smaller the number of growing degree days (GDD)[6]. Figure 3 shows annual rainfall and GDD for selected regions ranked in order of average MJT. Hastings River and Alpine Valleys both have relatively high rainfall for their position in terms of MJT, while conversely Coonawarra (SA) and Great Southern (WA) have relatively low rainfall for their position in terms of temperature.

Figure 3: viticultural weather indices for selected regions (average 19912017)

A drier than average season does not automatically equate to a smaller crush

There are a number of factors that can affect the size of the crush. In the 2018 vintage, reduced yields were widely reported across most regions as a result of a dry winter, lower cropping after a big crop in 2017, and some seasonal events. However, as reported in the Wine Australia Vintage Report, the total crush was just above the long-term average in terms of tonnes. Vineyard management strategies, such as irrigation and canopy management, can assist in mitigating the impacts of weather conditions.

Image: Ewen Bell / Wine Australia

Regional snapshots now available

Individual regional snapshots for 2017–18 are available for each wine region in Australia. These include the 2018 season climate/weather indices, as well as vineyard area, grape crush by variety and export statistics.

The updated, more accurate weather and climate information included in the snapshots has been provided as an outcome of the Wine Australia-funded project Australia’s wine future: Adapting to short-term climate variability and long-term climate change (2016–2019). The information generated enables current weather conditions to be understood within the context of historical averages. This is essential information for vineyard management and planning and also provides a baseline from which the effects of ongoing climate change can be measured.

Read more about the background to the project below and the project outcomes in an article from our RD&E News here.

Image: Andre Castelluci / Wine Australia

Background

Wine Australia’s regional snapshots have been updated to reflect recent improvements in the available climate data. The Bureau of Meteorology (BoM) automated weather stations (AWSs) are Australia’s key source of weather and climate information. It is well known that these locations have limited spatial and temporal representation, with offsets observed between most farms and the closest BoM AWS. A step towards addressing this issue was developed by the BoM in collaboration with the CSIRO, the Australian Gridded Climate Data (AGCD) product. The AGCD uses the relationship between many observations to provide the best estimate of weather conditions at any location across Australia (at a resolution of 5km2) from 1961 until present (regularly updated). Date from the AGCD improves the accuracy of weather and climate information at a regional scale while also making data across Australia more consistent for comparison purposes.

The wine region Geographical Indications boundaries were used to extract the relevant cells from the AGCD product. These were then aggregated to estimate the climate variables presented in the regional snapshots. This provides the best estimate of how each region’s climate has changed over the past 50 years and is useful for framing the magnitude of change projected into the future. 

Wine Australia identified the need for fine-scaled climate information about future conditions to help winegrowers plan for changes to mean climate conditions and variability. They funded a collaborative research project, Australia’s wine future: Adapting to short-term climate variability and long-term climate change (2016–2019). The project is led by the Antarctic Climate Ecosystems Cooperative Research Centre (ACE CRC, UTAS) in partnership with the South Australian Research and Development Institute (SARDI), the Australian Wine Research Institute (AWRI), CSIRO Marine and Atmospheric Research and the Tasmanian Institute of Agriculture (TIA).

The project will provide an understanding of short-term climate variability as well as trends in climate for the near and mid-term time scales across Australia. Key viticultural indices are being tailored for grapegrowers and winemakers in every wine region, with the focus on heat accumulation, heatwave and frost. Adaptation options to manage emerging risks in the near future and out to longer-term planning horizons are being identified with sector partners. This will help the sector identify appropriate adaptation responses within each region, to maintain grape yield, value and wine style into the future.


[1] 1961–1990

[2] New method divides regions into 5km2 blocks and measures weather variables separately for each block. Results are then compiled and averaged across a whole GI region to give a far more accurate indication of weather conditions than the old method of relying on a single weather station somewhere in a GI region

[3] 1991–2017

[4] 1961–1990

[5] 1991–2017 average period

[6] Growing degree days (GDD) are a measure of heat accumulation in plants. They are measured in degrees Celsius per unit of time (day) and accumulate over a season. Plants need a different number of GDD to ripen. Even within grapevines, different varieties have different thresholds. In this article GDDs are measured from October–April.


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