The Physics of Fog

By MetService Meteorologist Claire Flynn

While the weather conditions that lead to the formation of fog are usually quite benign, fog itself can be very disruptive. In particular the aviation and marine industries are often interested in how fog or mist will affect the visibility for their journeys, though fog also affects road-users. Fog can also make for some excellent photography opportunities, creating an eerie backdrop (as you can see in some of the photos below!)

Inversions

By Meteorologist Tom Adams.

How often have you gone to sleep on a calm night under clear skies, only to wake up and find the whole valley is full of fog?  This makes for great photos if you live above the cloud, as shown below from January 28th 2017 in Crofton Downs, Wellington, but it’s not so nice for the people living beneath the cloud.  Often the top of the fog is a smooth, flat surface, and is due to an ‘inversion’.  In this blog post we unravel what an inversion is, and why it leads to valley fog like this.