MEMPHIS, Tenn. (WMC) -When it comes to snow, many of us think if temperatures are above freezing than the snow should be gone , however there are a lot more variables that go into how fast or slow snow melts.
When substances undergo the melting process there are two main energy sources that are needed. The first is energy to bring the temperature to the freezing point from its current temperature and the other is the energy that does the actual melting. The energy in the second stage is referred to as Latent Heat of Fusion.
While several factors can play a role in snow melt, the primary factors are air temperature and the sun angle, the higher the sun angle the better for melting. As temperatures climb above freezing, heat from the sun begins to melt the snow and the higher the angle the more intense the sunlight, the faster it melts. The top layer absorbs the heat, causing the snow crystals to disintegrate. At first, the crystals will attach to individual water droplets. These drops will eventually cause some melting in the upper snow layers. Since snow melts from the top down, this process is repeated and each layer melts away.
Here are other factors that can determine how fast snow will melt
- Density of the snow the more water the heavier the long the snow will take to melt.
- Air temperature, of course above freezing temps will allow snow to melt faster. .
- Solar radiation: The heat from the sun heats us up and the amount of solar radiation will vary based on cloud cover as well as sun angle. The higher the sun angle, the more the solar radiation will heating whatever it touches.
- Wind speed: A stronger wind will allow for more melting thanks to the evaporation process
- Longwave radiation: Most of our warmth comes form the sun but Earth itself emits radiation because it’s warm core. The snow covered ground in the winter can acts as a barrier to that warmth from the earth which means snow can only melt from the top down, which adds to the time it takes to melt.
- Albedo: This is the term describes how reflective an object is. Fresh snowfall has one of the highest albedo of any naturally occurring substance on the Earth. It’s albedo number can be as high as 99 out of 100 which means that of all light is reflected back into space which includes the incoming solar radiation from the sun. Older and snow, has a lower albedo and can soak in more solar radiation and can melt faster.
Let’s get back to latent heat which is the main reason for the time it takes to melt snow. It’s takes a lot of energy and time to change a solid to a liquid in our atmosphere.
Ice doesn’t turn immediately to water when it hits 32°F. It has to have a certain amount of time to build up enough energy on the surface of the ice for the ice to change state over to a liquid. When you pull an ice cube out of the freezer, it doesn’t just immediately turn to liquid in your hand.
Warming ice up to 32° doesn’t take as much energy as it does to change the state of the ice from a solid to a liquid. This is why snow melt can be a long process.