There are days when we are all in a fog.

Even if your mind isn’t murky, there are other reasons for the haze in Vineyard Haven and all around our Island. Returning from holiday last Sunday, I was greeted with clouds at my feet.

Though that sounds heavenly, fog is not way above in the sky, but rather down low near the earth’s surface. Fog can be simply defined as ground-level clouds that are formed when air becomes supersaturated and no longer can hold any more water vapor. The extra water vapor becomes suspended at or near the surface, creating fog.

The clouds of water vapor that make up fog are formed from a different process than the clouds aloft in the sky. Fog is created when air is cooled to a temperature that is at or near the dew point (no more than five degrees Fahrenheit difference), and consequently can’t hold all of the water vapor it contains. Said another way, it is when the relative humidity reaches 100 per cent at ground level.

Poets and aviators find fault with fog. William Shakespeare had his three weird sisters in Macbeth establish confusion early on in his play by declaring: “Fair is foul, and foul is fair: Hover through the fog and filthy air.” Hovering in the fog is the last thing that airplanes want to do. It was fog that caused the 1945 crash of a B-25 Mitchell bomber into the Empire State Building and was responsible for a 1977 collision of two planes at the Tenerife Airport in the Canary Islands.

Those who travel by land or sea are not immune to fog-related disasters either. A collision in 1956 of the ocean liners Andrea Doria and Stockholm, and a 470-car pileup on Florida’s Interstate 4 in 2008, were both blamed on fog. Fog is described as vapor that is sufficiently dense to reduce horizontal visibility to less than 1,000 meters, or 3,281 feet, but for the general motoring public, much less visibility is what causes the most disruption. A reduction of sight of only 50 meters (164.5 feet) due to fog is very possib le and can be deadly.

There are as many fog types as there are cloud types in the sky. One can have radiation fog on clear, cool nights; but we have precipitation fog when it rains or snows. Location matters too. Valley fog occurs in valleys, and upslope fog along hills and mountains. Adduction fog results from humid air over cold ground or water; and steam fog, or sea smoke, happens when cold air drifts over warm water.

Though is seems as if the Island gets a lot of fog, we shouldn’t ever complain. Port Reyes, California has more cause to gripe since they get around 200 foggy days a year!

Perhaps fog’s greatest attribute, apart from adding an atmosphere of mystery wherever it appears, is its usefulness to writers as a source of metaphors: “Derive happiness in oneself from a good day’s work,” wrote Henri Matisse, “from illuminating the fog that surrounds us.” Joseph Conrad reminded us that “It is not the clear-sighted who rule the world. Great achievements are accomplished in a blessed, warm fog.”

And Timothy Geithner concurred, when he observed that “most consequential choices involve shades of gray, and some fog is often useful in getting things done.” The fog of war is a well-known and devastatingly appropriate image.

It is clear that fog can be an elusive presence in our lives, literally and metaphorically. Though the reasons for its emergence are transparent in its chemistry, when it comes to predicting when it will reappear, I can only say that I haven’t got the foggiest idea!


Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.