Ballarat’s Climate.
A vineyard’s climate is a major factor influencing how berries
mature, and the overall flavour profile and structure of the
resulting wine. The following pages explain a little about
Ballarat’s climate, and how it influences grape development and
therefore the finished wine.
Much of the following climatic data is based on observations from
official weather stations, and available from the Bureau of
Meteorology as historical averages. This data applies to the broad
general area, and is known as the Macroclimate.
Those who understand
Pinot Noir know that a cool climate is a critical part
of the jigsaw!
|
An individual site may have particular features that modify the overall
regional climate. These features would include things like:
Altitude
Aspect
Shelter
Whether the site was relatively flat or on a slope
Bodies of water (can moderate temperature
extremes)
This local climate, or Mesoclimate is specific to the individual site.
Indices relating to Phenological Development
Heat accumulation over the growing period of October to March gives a likely
indication of the ripening potential of a particular climate. The amount of heat
received in the warmest month has lead to the simple index of Mean January
Temperature (MJT) – July for the Northern Hemisphere. Climates are graded into
five categories, with a Cool Climate experiencing a MJT of between 17.0°C and
18.9°C (Smart and Dry, 1980).
One of the most common indices used is Heat Degree Days (Winkler et al,
1974). The basis of this index is that growth of vines is limited to above 10°C;
the amount of heat experienced above this baseline is summed for the entire
growing season.
Gladstones (1992) advocates the adoption of an index known as
Biologically
Effective Day Degrees. This index similarly sums the heat experienced over ten
degrees. However, Gladstones suggests that there is no further advance in
phenological development with temperatures above 19°C. He therefore suggests
this index with a cut-off at 19°C.
Sunshine Hours, or the number of hours of bright sunshine, is an important
index of the potential for photosynthesis. These figures are dependant on
latitude (Jackson and Spurling, 1988) and may typically be lower near the coast
due to increased cloud (Smart and Dry, 1980).
These indices (based on recorded weather data) all help to define the
potential for ripening in any given macroclimate - indices relating to different
areas are provided in Table 1. It should be noted that these indices provide a
general indication only. A particularly suitable site (e.g. north facing aspect,
gentle slope, sheltered from the wind) may have a specific mesoclimate more
suited to heat accumulation – the converse also applies. Further as these
indices are based on averaged data, in any given year, phenological development
may be advanced or retarded.
Comparison with other viticultural areas:
Table 1: Comparison of Climatic Indices for a number of vine growing areas.
1 - Raw figures
2 - Corrected for latitude, daily temperature range and "good-average" vineyard
sites (Gladstones 1992, p 70)
3 - Mean temperature of warmest month (February) appears in parentheses.
4 - Spring Frost Index (SFI). Higher figures indicate greater risk of frost.
Figures from Gladstones (2000), except
5 - Calculated from data in Gladstones (1992)
| |
Raw Day Degrees
(1) |
Corrected Day Degrees
(2) |
MJT
(3) |
Sunshine Hrs |
SFI
(4) |
|
Ballarat |
1072 |
1154 |
17.3 (18.3) |
1629 |
13.75 (5) |
|
Mornington |
1427 |
1435 |
18.8 (19.2) |
1420 |
11.55 (5) |
|
Hobart |
1017 |
1158 |
16.7 (16.8) |
1423 |
9.6 |
|
Launceston |
1156 |
1281 |
17.7 (18.2) |
1660 |
11.5 |
|
Blenheim (NZ) |
1101 |
1195 |
17.3 (17.4) |
1604 |
12.5 |
|
Portland (Oregon, USA) |
1179 |
1214 |
19.2 |
1660 |
10.2 |
|
Colmar (France) |
1186 |
1228 |
20.1 |
1369 |
|
|
Dijon (France) |
1164 |
1223 |
19.6 |
1449 |
12.1 |
|
Reims (France) |
1031 |
1191 |
18.8 |
1337 |
12.3 |
These indices give an indication of the potential to ripen fruit –
always an issue when you live on the edge. However, there are
compensations! Wines produced in the extremes of a cool climate tend to
retain higher levels of acid and have a different profile of flavours to
fruit from warmer climates. For example, cool climate Chardonnay would
tend to be more minerally and display more citrus like characters. These
more elegant wines are
natural combinations
with food – they marry with food rather than dominate.
The data above would indicate that Ballarat is particularly well suited
to the production of fine examples of Pinot Noir, Chardonnay, Pinot Gris
and Sauvignon Blanc (Gladstones, 2000). In particular, the delicate
flavours of Pinot Noir demand a cool climate, with maximum temperatures
below about 27°C during the ripening period for ideal flavour
development. Table 2 gives an indication of Ballarat’s Maximum daily
temperatures during the ripening phase.
Table 2: Maximum Daily Temperatures for Ballarat.
| |
January |
February |
March |
April |
|
Max Temp °C |
24.9 |
25.0 |
22.1 |
17.5 |
References:
Bureau of Meteorology (2001) Climate averages [online] available at:
http://www.bom.gov.au/climate/averages/
Gladstones J (1992) Viticulture and Environment Winetitles Adelaide
Gladstones J. (2000) "Past and Future Climatic Indices for Viticulture."
Paper presented at 5th International Symposium for Cool Climate Viticulture and
Oenology, Melbourne, Australia, January 16-20.
Jackson and Spurling (1988) "Climate and Viticulture in Australia" Chapter 4
in Viticulture (Volume 1: Resources) Coombe B.G. and Dry P.R. Eds. Winetitles
Adelaide
Smart RE and Dry PR (1980) A climatic classification for Australian
viticultural regions The Australian Grapegrower and Winemaker 196: 8, 10 & 16
Winkler AJ, Cook JA, Kliere WM and Lider LA (1974) General Viticulture 2nd
edition University of California Press Berkeley cited in Jackson DI and Spurling
MB (1988) "Climate and Viticulture in Australia" Chapter 4 in Viticulture
(Volume 1: Resources) Coombe B.G. and Dry P.R. Eds. Winetitles Adelaide
