Fog and Thermodynamics

Winter has arrived at Bear Lake.  So far my predictions of above average snow made by observing the number of pine squirrel invading my yard is holding true.  I am just relieved that I don't need to hear about drought and climate changes when the news stations have nothing else to report on.

Winter in Bear Lake has a number of characteristics that don't change from year to year.  The fog is the most prominent one.  Now a quick lesson in thermodynamics.  As the surface water temperature on the lake is warmer than the air temperature condensation starts to occur.  Lots of people will say "the lake is steaming" which is incorrect.

 Vaporization occurs when a liquid is heated to its boiling point at which time the liquid turns into a gas.  Condensation is when a gas turns to a liquid by cooling.  On a cold winter morning,  evaporation is occurring on the lake as long as it is liquid not ice covered.  Evaporation is when a water surface turns from a liquid, directly to a gas.  Another unique characteristic of water.  The water from evaporation is turned into a liquid from gas by the cold air.  These little droplets or ice crystals form the fog we see.

We will see this cycle occur frequently as the winter progresses and the lake approaches freezing.  Depending on the day, wind and temperature the whole Valley will be filled with "cotton" as you look at it from the over look. 

Some days, the fog will hang over the valley, drift to the valley floor during the night and when it lifts in the morning everything is covered with hoarfrost.  Hoarfrost occurs when condensation (when the lake is evaporating and cooling) freezes to solid items whose temperature are below the dew point.  That is why when we have these spectacular mornings with hoarfrost on everything you can actually determine which materials hold heat better.  Dark limbs have less than light colored limbs and so on.

One last observation.  Most of us have seen Grandma hanging out her clothes in the middle of the winter only to have them freeze solid and then dry.  This dynamic activity is called sublimination which is when water goes from a liquid to a solid and then due to cold from a solid directly back into a gas.

You get to experience a lot of things living next to a large temperate lake.  Luckily water is such a unique matter and a more extensive education in physics and thermodynamics will help you understand why.  Yea, I know, we all hated physics.  I hope you look a fog and winter days differently now.