Understanding the science behind frost formation
We’re amidst frost season in Atlantic Canada, which I recently mentioned has started earlier than normal this year.
Have you ever been curious just how frost forms and what factors go into it being a frosty night or not? Let me explain.
Frost most often forms on nights when the sky is clear, winds are light and usually during the presence of high pressure.
A clear sky allows the heat received during the day to escape back toward space and cooler air to sink to the surface. If clouds are present, they act
like a blanket and will send some of the radiated heat back to the surface, making it difficult for frost to form.
The little-to-no wind is also necessary as a breezy or windy night mixes the airmass and prevents the surface from getting as cool.
As the temperature drops, it will often cool to what’s known as the dew point – known as the frost point, in this case. When the temperature meets the dew point, water vapour condenses, and if the surface is at or below freezing, then the water droplets will freeze onto that surface and form frost.
The most common type of frost we experience is known as hoar frost or radiation frost.
Hoar frost forms when water vapour meets a surface or object below freezing and that water vapour immediately freezes and forms ice crystals through the process known as a deposition.
Like other variables in weather, frost can have a detrimental impact on the agricultural sector and even your home garden.
The freezing temperatures cause the water inside and outside the plant to freeze, and the ice that forms can puncture plant cells that can ultimately devastate a productive crop in one or two nights.