Winter Fog

[sledhead007]

John,

On the drive home from work last night it was -2 outside and there were numerous areas where it was foggy. Just wondering what would have been causing the fog with temps that cold, I did not know it was possible to have fog in those types of condtions..

-Sled

 

[jd]

Well, you start to get into some pretty thick physics as to why it is so, but in order for water vapor (fog) to go right from the vapor form to a solid (ice crystal), a process that is called deposition, there needs to be what is called an ice nuclei. That can be another ice crystal, speck of dust, tiny bit of salt, etc... Without that ice nuclei, the air temps actually need to be well below zero (around 40 below) for that deposition to occur.

-John