Temperature and Snow Cover
Snow cover is a radiative sink. Its high short-wave albedo is combined with a high thermal emissivity which increases the amount of infrared radiation lost near the Earth's surface. The radiative losses are not replaced quickly by heat fluxes from below because of the thermal insulating properties of the snow. It is a particularly good insulator at night when radiative exchange is concentrated in the surface layers of the snow. The temperature of the snow surface may drop by > 10°C overnight, but the soil surface underlying snow cover as thin as 10 cm may drop by < 1 °C. When the melt occurs, the snow cover is a sink for latent heat because of the large amounts of energy required to change water phase. The surface energy balance is, thus, very strongly influenced by changing distributions of snow cover. Surface exchange processes are further modified by the small aerodynamic surface roughness of snow cover.
ES students went over 20 years of Whitehorse weather data to record temperature changes following October and November snowfalls and the changes in daily temperature. They found considerable varibility. Many of the snowfalls came fro air masses moving in from the west and south west from the ocean. These were often warmer air masses, that were followed by cooling temperatures with the influx of air masses from the north. We were unable to conclude that the increased snow related albedo resulted in decreased temperatures.
Snow cover is a radiative sink. Its high short-wave albedo is combined with a high thermal emissivity which increases the amount of infrared radiation lost near the Earth's surface. The radiative losses are not replaced quickly by heat fluxes from below because of the thermal insulating properties of the snow. It is a particularly good insulator at night when radiative exchange is concentrated in the surface layers of the snow. The temperature of the snow surface may drop by > 10°C overnight, but the soil surface underlying snow cover as thin as 10 cm may drop by < 1 °C. When the melt occurs, the snow cover is a sink for latent heat because of the large amounts of energy required to change water phase. The surface energy balance is, thus, very strongly influenced by changing distributions of snow cover. Surface exchange processes are further modified by the small aerodynamic surface roughness of snow cover.
ES students went over 20 years of Whitehorse weather data to record temperature changes following October and November snowfalls and the changes in daily temperature. They found considerable varibility. Many of the snowfalls came fro air masses moving in from the west and south west from the ocean. These were often warmer air masses, that were followed by cooling temperatures with the influx of air masses from the north. We were unable to conclude that the increased snow related albedo resulted in decreased temperatures.