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Home > Food & Agriculture > Horticulture > Wine Industry > Vineyard Climates

Vineyard Climates

Temperature
Calculating Growing Degree Days
Averages and Variability
Long Term Climate
Further Information

Vineyard Climates in Tasmania

The Vineyard Climates of Tasmania poster was presented at the International Conference on Cool Climate Viticulture and Oenology in Melbourne in 2000.

Below is a print-friendly version of the Vineyard Climates of Tasmania poster presented by Duncan Farquhar and Ian Barnes-Koeghan. Warning: This is a large file and may take some time to download. If you are having problems downloading the file, please contact the officer below.

Download Vineyard Climates of Tasmania as a PDF  Vineyard Climates of Tasmania
(PDF: 3.10 MB / 1page)
 
This is a Portable Document Format (PDF) file and requires the use of Adobe Acrobat Reader. The Reader is easy to download and is free of charge.
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Temperature

Temperature is a key driver of metabolic processes in plants. The chemical reactions of life occur at faster rates at higher temperatures. In grapes it is commonly considered that growth effectively stops when temperatures fall below 10 degrees. Growing Degree Days (GDD) is a temperature index that shows how much effective growing temperature a plant has been exposed to during a given period.

Below is a Print-Friendly version of a Climate Map of Tasmania that shows how effective temperature (growing degree days) varies from region to region across the State. Values between suitable Bureau of Meteorology weather records were estimated using elevation as a surrogate for temperature.

Download GDD Map of Tasmania as a PDF  GDD Map of Tasmania
(PDF: 302 KB / 1 page)
 
This is a Portable Document Format (PDF) file and requires the use of Adobe Acrobat Reader. The Reader is easy to download and is free of charge.
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Calculating Growing Degree Days

GDD is calculated by subtracting 10 degrees from the observed temperature (if the observed temperature is above 10 degrees) and dividing this figure by the time (measured in days) that this temperature was maintained. For example, if the temperature is 11 degrees for a whole day, one day degree has been experienced. An accurate measure of GDD would be obtained from a continuous measurement of temperature with time and calculating the area under this plot and above 10 degrees. These continuous temperature tracks are not readily available. Standard measurements of temperature are available from the Australian Bureau of Meteorology weather stations. These measures include a daily maximum and daily minimum temperature. For the plot below, average daily temperature is calculated from the midpoint between this maximum and minimum temperature measure. Using this average temperature GDD is able to be calculated for each day by subtracting 10 degrees from this average temperature. For days where the average temperature is below 10 degrees no GDDs are accumulated. To calculate whole season GDD, the GDD for each day from July to June in a given one year season are added. These whole season GDDs are plotted in the figure below.
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Graph showing full year heat summation above 10 degrees celcius at Hobart Airport, Swansea Post Office, Scottsdale and Launceston Airport.


Averages and Variability

The mean GDD for the years plotted above (1989-2002) was 1001 for Launceston Airport, 1275 for Swansea, 1088 for Scottsdale and 1230 for Hobart Airport. It is clear from the plot however that each site varies considerably around each mean. This variability can be summarised into a statistic called variance. The variance is calculated as the average squared deviation of each number from its mean. Standard deviation is calculated as the square root of this statistic, 68 percent of the values are within one standard deviation of the mean. For these stations and these years the standard deviations in GDD are 102 for Launceston Airport, 109 for Swansea, 124 for Scottsdale and 131 for Hobart Airport.

Mean
Standard Deviation
Launceston Airport
1001
102
Swansea
1275
109
Scottsdale
1088
124
Hobart Airport
1231
132


Temperature and its variability is an important part of the risk associated with viticulture in Tasmania and an important influence on wine quality.
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Long Term Climate

Pencil Pine chronology from Mt Field, up to 1976. From initial investigations (mine and LaMirche and Pittock 1980), the dominant response is to summer temperatures in the current growing season (max and min slightly different). Note this is NOT a temperature reconstruction.


Mt Field Chronology

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For Further Information:

Contact: Horticulture Branch Enquiries
Dugald Close
Program Leader (Horticulture)
13 St Johns Avenue NEW TOWN TAS 7008
Phone: 03 6233 0838
Fax: 03 6228 5123
Email: Dugald.Close@dpipwe.tas.gov.au
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This page - http://www.dpipwe.tas.gov.au/inter.nsf/WebPages/CPAS-5JM2L9?open - was last published on 1 October 2009 by the Department of Primary Industries, Parks, Water and Environment. Questions concerning its content can be sent to Horticulture Enquiries by using the feedback form, by mail to GPO Box 44, Hobart, Tasmania, Australia 7001, or by telephone to 03 6266 4305.

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