Snow cover
Winter in Quebec comes with periods of extreme cold and abundant snow. This snow, and the way it accumulates, plays an important role from an economic, environmental and cultural point of view.
The characteristics of fallen snow, such as its thickness, density and grain size, vary throughout the winter. Regular monitoring of these characteristics is important for winter activities, infrastructure, buildings, agriculture and the water supply to hydroelectric dams.
Definitions
Snow cover: According to the Canadian Encyclopedia, snow cover is the term used to describe the accumulation of snow on the ground resulting from solid precipitation. It can be described in terms of its depth or using its snow water equivalent as an indicator.
Snow water equivalent (SWE): The amount of liquid and solid water present in the snow cover, obtained by melting a snow sample taken at a weather station.
Some benefits of snow cover
Snow cover provides many benefits to societies and ecosystems, including:
A water reserve: The snow cover that accumulates in the winter constitutes a large reserve of water, which is released when it melts in the spring. The measurement of its SWE is used in the management of hydroelectricity and irrigation.
Help with flood prediction: Data on melting rates can help predict floods. The spring melt, which is generally rapid, lasts from a few days to two weeks.
An excellent thermal insulator: Snow protects plants, animals and humans from cold temperatures. It allows certain plants to remain active in winter and small animals to move around under an insulating cover. When the Inuit travel to hunt, they still build igloos for protection from the cold.
An asset for winter activities: Winter activities, such as snow forts, snowball fights and tobogganing and winter sports like skiing and snowmobiling, are fun and make winter enjoyable. They also support the development of the recreation industry in Quebec.
The snow cover: cooling the air
Due to its high reflectivity, with an albedo of 80 to 90% for fresh snow, average air temperatures near a snow-covered surface are typically 5 to 10°C colder. If the snow cover is very extensive, cold air can move over large distances without warming up.
However, due to increasing temperatures, the extent of the terrestrial snow cover is decreasing in the Arctic in spring. Combined with the decreasing surface area of sea ice, this is amplifying the warming of the air in this region.
This is why snow cover is recognized as a major element of the Earth’s climate. It is also one of the main sources of climate feedback, meaning that it influences other climate variables such as air temperature.
Measuring the thickness of the snow cover
Since the early 20th century, Quebec has had weather stations that measure air temperature, the quantity and intensity of precipitation, as well as the characteristics of the snow cover. The oldest station still in operation is called Barrage Angliers, located in Témiscamingue. It opened on February 15, 1911. It is worth noting that snow cover can also be measured by satellite.
Snow cover measurements determine its thickness, density and snow water equivalent. This work begins in late January and continues twice a month until the snow cover disappears.
However, snow cover varies greatly over space and time. Snow does not fall evenly across the land, given its volatility and the obstacles in its path. For example, wind contributes to its redistribution and compaction, while topography and vegetation cover affect its accumulation. Once snow is deposited, weather conditions change its density, thickness and the amount of water it contains.
Thus, the measurements taken at one station are not representative of an entire region or an entire season.
However, these observational measurements are very useful for modelling snow cover.
Snow water equivalent
The most frequently considered variable in studies and projections on snow is snow water equivalent (SWE). The SWE provides information on the quantity of water available in the snow cover. This water reserve plays a role in a region’s hydrological cycle with regard to things like flooding, drought, water availability for hydroelectricity, and runoff.
