Climate in the Niagara Peninsula wine region

Climate, according to Dr. Tony Wolff (Lecturer and Viticulturist, Virginia Tech) and John D. Boyer, is the average course of weather in a region over an extended period as measured by temperature, precipitation, and wind speed, among other variables (Vineyard Site Selection, Virginia Cooperative Extension).  Weather is itself defined as the state of the atmosphere at a specific point in time using the same variables as referenced in the climate definition above.

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.

Niagara Peninsula bounded to the north and south by
Lakes Ontario and Erie
(Source: Google Maps screenshot)

VQA Ontario identifies a closed-loop system of air movement over Lake Ontario and the adjacent landforms. Warm air over the lake rises and cold air resident over the land rushes in to take its place. The warm air then moves inland to occupy the space vacated by the cold air, modifying temperatures "several kilometers inland." The concept is illustrated in the figure below.

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.

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.

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

Macro-climates and their modifying agents

Climate, according to Dr. Tony Wolff (Lecturer and Viticulturist, Virginia Tech) and John D. Boyer, is the average course of weather in a region over an extended period as measured by temperature, precipitation, and wind speed, among other variables (Vineyard Site Selection, Virginia Cooperative Extension). Weather is itself defined as the state of the atmosphere at a specific point in time using the same variables as referenced in the climate definition above. The climate of a grape-growing region will determine, to a large extent -- and all things being equal -- both the grape varieties that can be grown and the styles of wine that can be produced.  That is not to say that these varieties cannot be grown outside of these environments; that is to say, however, that varietal typicity is compromised when these varieties are grown outside of their "zones."  In this post I will examine macro-climatic effects in greater detail and describe the agents which affect their impacts.

Macro-climate refers to climatic effects over large (hundreds to thousands of miles) geographic areas.  The table below shows a climate classification scheme based on the governing temperatures during the berry-growing season and examples of wine-growing regions that fall within the various climate bands.

Climate can also be described in terms of its "continentality", as shown in the table below.

Maritime climates 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.  This effect is not only limited to maritime areas, however, as regions that adjoin lakes and rivers will also be subject to similar effects. Franciacorta, for example, is moderated by winds blowing in off Lakes Iseo and Garde which protect the region from the autumnal and hibernial fogs that threaten from the Brescian Plains. Further, in the case of rivers, the water flow promotes air movement.  The downside associated with proximity to bodies of water is increased humidity levels and the risk of fungal diseases.

Offshore ocean currents can also have a moderating effect on a climate.  For example, the cool air blowing in from the Pacific Ocean mixes with the warmer air blowing in from the San Joaquin Valley creating an early morning fog in Napa's Oakville AVA.  This fog blows off by the middle of the day, allowing the grapes to gain the ripening benefit of the afternoon sun.  At the peak of the afternoon temperature, cooler air is once again funneled into the region from San Pablo Bay.  The Humboldt current off the coast of Chile serves much the same purpose for its regions, allowing grape growing in areas that would be otherwise too hot.

Mountains play a variety of roles in modifying a region's climate.  In the case of Alscae, the Vosges Mountains blocks the wine growing regions from the prevailing westerly winds but also provides a rain shadow effect which keeps most of the rainfall to the west side of the mountain and away from the vineyards. In the case of Oregon's Willamette Valley, climate is moderated by three openings in the Coast Range which provide gateways for the transit of cool air between the Pacific Ocean and the valley. The opening between Lincoln City on the coast and Salem in the valley is named Van Duzer Corridor. The remaining two (un-named) corridors run from Newport to Corvalis and Florence to Eugene, respectively.  Finally, temperature decreases by 33.08°F (0.6°C) every 328 feet (100 meters), thus allowing vineyards to be planted on mountain sides in areas where conditions would otherwise be uncooperative.

Forests can be the bane of vineyards in that they harbor birds but, as in the case of Bordeaux's Medoc, the forest to the west of the region serve as a barrier to the winds blowing in off the Bay of Biscay.

Vineyard selection and management practices can also work to blunt the effects of climate.  For example, by being on an appropriately sited slope, the vineyard can gain access to the sun's rays earlier and for longer periods of time thus aiding the ripening process in cooler climes.  A vineyard on a slope can also benefit from cold air moving downhill and being replaced by warmer air.  That zone of warmth can be hospitable for vine growth and berry ripening. 

Canopy management and trellising techniques could provide the berry with more or less access to the sun or protection from the elements as required.  For example, a significant challenge to Santorini viticulturists is the stiff wind that buffets the island during the growing season and could damage the berries if they were exposed to the elements. The solution that has been employed for eons is to (i) eschew vine density and (ii) train the vines such that they can afford protection to the otherwise vulnerable berries. Vine canes are intertwined and trained into a circle and the berries grow within this protective cordon. The circular structure can be positioned above ground or in a below-ground hollow where the top of the vine is parallel to the surface.

As it relates to the wine regions of the world, the ideal macro-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.  Grapes are, however, grown in a variety of areas which do not fit this profile, a situation made possible by a mix of natural events/edifices and human ingenuity.

©Wine -- Mise en abyme

The science of viticulture: Climate and site selection

Quality grapes are a precursor of quality wine and the science of viticulture has developed and evolved with a single goal in mind: the delivery of high-quality wine grapes to the winery.  The quality of wine grapes produced in a specific harvest is not only a function of that year's harvest conditions.  Rather, it is the result of a combination of factors which, together, represent the full scope of viticultural science.  I will cover most of the inherent elements of viticultural science in a series of posts as a part of my investigation of the source of grape-derived odors.

There are three major areas of concern for the viticulturist as he/she sets about the task of delivering quality grapes to the winery door: (i) selecting the site which will best ensure goal attainment; (ii) setting up the vineyard with the appropriate elements such that cost-effective goal-attainment is promoted; and (iii) implementing a cost-effective, repeatable vineyard management regime which is reflective of the operating conditions.  Within these major considerations there are a number of sub-elements where the rubber really meets the road and I will focus our coverage of the topic on these areas beginning with today's writeup on climatic considerations in site selection.

The site selected for a new vineyard will determine the amount and quality of fruit produced, the resources required to manage the vineyard, and, ultimately, the profitability of the vineyard.  Selecting a site for a new vineyard is generally a compromise between a number of factors.  For example, most of the exceptional vineyard sites in the world have been under vine for many a year, leaving less-than-perfect options available for the aspiring vineyard owner.  Second, most prospective vineyard owners are drawn to sites that are readily accessible to them and this limiting facor comes with a given climate.  And so on.  Site selection is thus the process of making an optimal choice within the bounds provided bythe needs of the wine grapes, the available site options, and associated limiting factors. 

Source: Compiled from arcserver2.iagt.org

The key site-selection factors for consideration are climate and site physical characteristics.  Climate, according to Dr. Tony Wolff (Lecturer and Viticulturist, Virginia Tech) and John D. Boyer, is the average course of weather in a region over an extended period as measured by temperature, precipitation, and wind speed, among other variables (Vineyard Site Selection, Virginia Cooperative Extension).  Weather is itself defined as the state of the atmosphere at a specific point in time using the same variables as referenced in the climate definition above.  The climate of a grape-growing region will determine, to a large extent -- and all things being equal -- both the grape varieties that can be grown and the styles of wine that can be produced.  For example, Syrah appears to flourish in warm climates while Riesling does best in cold.  That is not to say that these varieties cannot be grown outside of these environments; that is to say, however, that varietal typicity is compromised when these varieties are grown outside of their "zones."

As it relates to the wine regions of the world, the ideal climates for vitis vinifera are Mediterranean and marine west-coast climates which are both 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.

Source:www.buywineonline.co.uk

In viticulture, three separate aspects of climate are normally considered: macro-climate, meso-climate, and micro-climate.  Macro-climate refers to climatic effects over large (hundreds to thousands of miles) geographic areas and are either continental or the aforementioned maritime.  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.

Meso-climate covers a much smaller area than does macro-climate and is generally the scale at which site decisions are made.  It is at this level that that the physical aspects of the surroundings -- elevation, slope, aspect -- can temper broader macro-climatic effects.  The climatic effects of these physical elements will be covered when they are discussed individually.

Micro-climate are the conditions that exist in the vineyard from the soil upward into the vine canopy and, as such, is more relevant when the land is under vine than in the site-selection phase.

One of the key grape needs is adequate sunlight and heat to allow both the fruit and the vegetative aspects of the plant to mature.  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 the site-selection dialogue.

Source: Compiled from oregonviticulture.net

These then are the broader climatic considerations for the viticulturist in selecting a site for a new vineyard for the production of quality wine grapes.  The physical characteristics that should be evaluated will be covered in the next post on viticultural science.


© Wine -- Mise en abyme