A offbeat look at the phenomenon of fog and the science behind it...
"There's something in the fog!" screams Stevie Wayne in the classic John Carpenter horror The Fog. The film plays on that ever so ingrained primal fear of isolation and disorientation that fog is associated with. Though,
as it turns out, this coastal romp isn't a meteorologically accurate account of the visibility reducing weather phenomenon. I mean everyone knows that no fog can move against the wind...
Actually any significant wind at all will tend to disperse fog as a rule. It is essentially nothing more than cloud at ground level, a stratus cloud. And as with clouds in the sky a firm breeze will scatter it fairly quickly.
Stillness is very much a requirement for the formation of fog as it is made up of tiny water droplets. These droplets are so small and weigh so little that they remain suspended in the air. Light reflects off these particles and creates the opaque vale.
Referring back to Carpenter's The Fog, the title is in part accurate. The term fog should be used in an official capacity when visibility is reduced to less than one kilometre, which in the movie it certainly is. If visibility exceeds this, then the correct term to use is mist.
So how does fog happen? It has a lot to do with dew points, the point at which cooling air condenses its water vapour into liquid. If the difference between the air temperature and dew point is less than two and half Celsius the chances are you're going to have a fog.
There are of course a number of other factors that contribute to the formation of fog. For example the proximity of water, this increases the chances of fog occurring due to the greater humidity in the air. Presumably this was why The Fog was set by the sea, meteorological accuracy.
Being closer to sea level also alters fog, tending to make it thicker. This means in geographical features such as valleys or bowls, or anywhere where ground level is lower than the immediate surrounding area fog increases in density. This is because foggy air is heavier and flows downward.
The foggiest land area in the world is hard to call but Point Reyes, California and Argentia, Newfoundland are considered as the main contenders. They both experience well over 200 foggy days a year. Although that sounds a little miserable, it does also have benefits. Coastal communities in California use fog nets to trap the moisture to supplement their water supplies.
As for the foggiest place in the world? That is Grand Banks, an area off the coast of Newfoundland. It is where the cold Labrador Current from the north and the much warmer Gulf Stream from the south meet, and when they do fog is almost a certainty.
So there you have it, fog is a little bit spooky, but it's mostly just floating water vapour produced when warm and cold air get together. Though it has occurred to me that maybe it's less the fog that's sinister, and more what might be lurking in it...
