The climate change irony - more frost

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Frost continues to affect quality and yield in winter crops around Australia each year, but GRDC funding, along with funding from the grape and wine industry, aims to give growers a greater understanding of the meteorological drivers of frost while examining how frost risk is changing now and in the future

By Kellie Penfold

 

The irony of climate change is that while average temperatures rise, CSIRO scientists have found that southern Australia is experiencing an increase in the frequency of late frosts (Figure 1) and, in some areas, an increase in the number of frosts (Figure 2).

New frost research funding is being provided by the GRDC and the Grape and Wine Research and Development Corporation through the CSIRO Climate Adaptation National Research Flagship program. Steven Crimp is the research team leader for farming systems (southern region) at CSIRO Sustainable Ecosystems. He says the new funding will provide a greater understanding of how frost occurrence is changing in southern Australia and how to reduce risk in agriculture, especially in the grains and wine industries.

The current hypothesis is that the increasing frequency of late frosts is driven by a long-term southerly shift in position and intensification of the band of high pressure typically located over central Australia in spring. Southerly displacement of this band of high pressure has potentially resulted in the increased intrusion of polar air masses from circulation about the pressure systems.

This, Dr Crimp says, is likely to be the result of a warmer atmosphere. When combined with lower growing-season rainfall, the impact of frost on crops at flowering or grain fill can be devastating. What is of concern is that, as average growing season conditions warm, the growing season shortens (that is, it is estimated that plant growth stage moves forward by seven days for every 1ºC of warming). When combined with earlier or dry sowing, it means flowering or grain fill is being brought back into the period of higher frost risk.

“Moisture in the soil helps to ameliorate the impact of frost. Drier soils cool more rapidly and plants holding less moisture freeze more quickly,” Dr Crimp says.

By analysing historical weather data, CSIRO has identified that in a number of regions the first frosts of the year are occurring earlier and the last frosts later.

The new CSIRO Climate Adaptation frost research is based on finding answers to the following questions.

• What are the key synoptic-scale climate drivers responsible for historical frost occurrence?

• Are these drivers likely to persist, reduce or be enhanced in response to enhanced greenhouse gas concentrations – that is, is this a transient feature?

• How will these changes in frost risk interact with production risk?

• What adaptation options are available to offset risk?

Dr Crimp says this research will help to improve experimental frost forecasting systems and, when combined with local frost knowledge, will make a useful risk-management tool.

The Bureau of Meteorology (BoM) is currently trialling Frost Potential, a web-based frost-prediction tool. The Frost Potential maps show forecast low temperature thresholds for various Australian weather station locations. The maps are updated each day and show forecasts for the next 48 hours. Coloured dots on the maps indicate the lowest temperature range for each location and forecast temperatures are for the standard 1.2 metres above the ground. Near the ground the temperature may be up to 2ºC lower.

Users can move their mouse cursor over the dots in the state and territory views for further details for each weather station location or click the frost table link to view all the details for that state or territory.

In addition to the forecast minimum temperature, the details include the number of hours below each temperature threshold. BoM is asking for feedback on this service and its relevance to users.

 

GRDC Research Codes MCV00010, CSP00131

More information: Dr Steven Crimp, 02 6242 1649, 0428 482 940, steven.crimp@csiro.au, www.csiro.com; www.bom.gov.au/jsp/watl/weather/frost.jsp

Region National, North, South, West