Excerpt from ‘Cool Climate Australia’, which first appeared in the Drinks Business, January 2008.
Drs. Amerine and Winkler (1944) defined five regions of California using a temperature index. Using a seven month growing season, they calculated the ‘degree days’ above 10°C (at which temperature vines generally start growing). Mean monthly temperature less 10 (degrees) multiplied by the number of days in the month, and totalled for the seven months.
They came up with five regions, which still form the bedrock of viticultural climatic data. Their system has been variously refined, amended and critiqued, but not abandoned.
Region I is the coolest. Each region can be matched to the mean temperature of the warmest month (MJT) – January or July. From the regions that fit into the model, typical grape varieties can be identified.
|Region||degree days||MJT °C||grape varieties||wine regions|
|Region I||<1390||<19.8||pinot noir, riesling, chardonnay, gewurztraminer, pinot grigio sauvignon blanc||Chablis, Friuli, Tasmania, Champagne, Marlborough|
|Region II||1391 to 1670||19.9 to 21.3||cabernet sauvignon, chardonnay, merlot, semillon, syrah||Bordeaux, Alsace, Yarra Valley, Frankland River|
|Region III||1671 to 1940||21.4 to 22.8||grenache, barbera, tempranillo, syrah,||Clare Valley, Lower Hunter, Rioja, Piemonte|
|Region IV||1941 to 2220||22.9 to 24.3||carignan, cinsault, mourvedre, tempranillo||McLaren Vale, Upper Hunter, Langhorne Creek, Montpellier|
|Region V||>2220||>24.3||primitivo, nero d’avola, palomino, fiano||Greek Islands, Jerez, Sicily, Sardinia|
Source: paper by Dr. Andrew Pirie – ‘Defining Cool Climate’. Stratford’s Brave New World seminar, London, September 2007
Dr. John Gladstones developed the model for Australia. Drs. Peter Dry and Richard Smart developed a homoclime approach, using a range of climatic measures including radiation, rainfall and relative humidity. Pirie brought in growing-season rainfall and humidity to the blooming algebraic calculation, to account for low vine-moisture stress during growing time.