The climate of a grape-growing region will determine, to a large extent, both the grape varieties that can be grown and the styles of wine that can be produced. The climatic requirements for successful viticulture include: a growing season long enough to mature both the fruit and vegetative aspects of the plant; production of sufficient carbohydrates to ripen the fruit as well as to maintain future productive potential; and an adequate supply of water.
The general consensus is that the ideal climates for vitis vinifera are Mediterranean and marine west-coast climates, both of which are characterized by mild, wet winters and warm, dry summers. The mild winters promote long-term survivability of the vines (and increased quality of the juice as the vines age) and the wetness provides a reservoir of water that the vine roots can tap into during the grape maturation cycle. The warm, dry summers provide the heat and light that are the engines of vegetative and crop growth while keeping at bay the threat of rot and flavor dilution that would accompany summer/fall rains.
Continental climates are modified by large land masses and are characterized by hot summers and cold winters. Maritime climates, on the other hand, are modified by proximate large bodies of water which heat up and cool down at a slower rate than does the adjoining land mass. This scientific fact results in the warming of winter winds as they blow over a warmer body of water and the warming of landside vineyards as the winds make landfall. This warming could act to extend the growing season and minimize the potential vine impact of winter low-temperature events. On the other side of the coin, warm spring air blowing in over the still-cold water will be cooled down and will retard the development of landside vineyards, minimizing their potential for damage from spring frosts.
The Niagara Peninsula exists in neither a Mediterranean or west-coast marine climate environment; it is decidedly continental. However, the peninsula is bounded by two lakes and those lakes act like heat sinks in moderating the temperature of the surrounding land, cooling it in the summertime and warming it in the winter. In addition, the lakes act as a giant humidifier, increasing the moisture content of the air.
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| Niagara Peninsula bounded to the north and south by Lakes Ontario and Erie (Source: Google Maps screenshot) |
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| Air flows in the vicinity of the Niagara Escarpment (Source: Dr. Tony Shaw, Diagrams and Technical Information for the Niagara Peninsula) |
Niagara Peninsula climate is also modified by temperature inversions. The ground that is distant from the lake cools rapidly overnight by radiating energy upwards. This results in a warm-air being sandwiched between the cooler air above the canopy and the cold air at the surface (Shown in the figure below). In flat areas, this inversion effect warms the canopy and fruit layer of grape vines. In areas with sloping ground, the lower layer of cool air travels downhill and is replaced by the warm air.
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| Temperature inversion (Source: shsu.edu) |
Growing Degree Days
Two key grapevine needs are adequate sunlight and heat to allow both the fruit and the vegetative aspects of the plant to mature. Vitis vinifera requires a minimum of 1250 hours of sunshine to provide ripe fruit. The progression of the grape through its various stages of maturity is influenced by the ambient temperature with research indicating that growth of the grapevine begins when temperature exceeds 10℃. A measure -- growing degree days (GDD) -- has been developed to measure the accumulation of heat (as measured by temperature) in excess of 10℃ over a growing season. Extensive research has yielded the following GDD parameters which can be used as input in vineyard site selection.
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| Source: Compiled from oregonviticulture.net |
Niagara Peninsula, with 1590 growing degree days, is well within the top class of wine quality potential.
©Wine -- Mise en abyme
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