My Fog Blog
One of the first things we noticed about living in the West Virginia
Eastern Panhandle was that it sure seemed too be foggy a lot. I tried to capture the mood and feel of the
fog. I looked out on the Internet to see
why it formed. Of course I had to write
this blog to share it with you all.
Don’t get me wrong. I have lived
a lot of places where fog formed.
Arizona, California, Florida, Okinawa, Utah, and beyond, all get
fog. It seemed like the conditions in
West Virginia led to more fog than was usual to my experience in the first few
months of living here.
Fog
“Fog is a cloud that touches the ground. Fog can be thin or thick,
meaning people have difficulty seeing through it. In some conditions, fog can
be so thick that it makes passing cars. Even monuments like London Bridge, in
London, England, or the Golden Gate Bridge, in San Francisco, California, are
almost impossible to see in thick fog.
Fog shows up when water vapor, or water in its gaseous form, condenses.
During condensation, molecules of water vapor combine to make tiny liquid water
droplets that hang in the air. You can see fog because of these tiny water
droplets. Water vapor, a gas, is invisible.
Fog happens when it’s very, very humid. There has to be a lot of water vapor
in the air for fog to form.
In order for fog to form, dust or some kind of air pollution needs to be
in the air. Water vapor condenses around these microscopic solid particles. Sea
fog, which shows up near bodies of salty water, is formed as water vapor
condenses around bits of salt.
Depending on the humidity and temperature, fog can form very suddenly
and then disappear just as quickly. This is called flash fog.
Fog is not the same thing as mist. Fog is denser than mist. This means
fog is more massive and thicker than mist. There are more water molecules in
the same amount of space in a fog. Fog cuts visibility down to one kilometer,
meaning it will prevent you from seeing further away than one kilometer from
where you’re standing. Mist can reduce visibility to between one and two
kilometers.
Types of Fog
There are several different types of fog, including radiation fog,
advection fog, valley fog, and freezing fog.
Radiation fog forms in the evening when heat absorbed by the Earth’s
surface during the day is radiated into the air. As heat is transferred from
the ground to the air, water droplets form. Sometimes people use the term
“ground fog” to refer to radiation fog. Ground fog does not reach as high as
any of the clouds overhead. It usually forms at night. Fog that is said to
“burn off” in the morning sun is radiation fog.
Advection fog forms when warm, moist air passes over a cool surface.
This process is called advection, a scientific name describing the movement of
fluid. In the atmosphere, the fluid is wind. When the moist, warm air makes
contact with the cooler surface air, water vapor condenses to create fog.
Advection fog shows up mostly in places where warm, tropical air meets cooler
ocean water. The Pacific coast of the United States, from Washington to
California, is often covered in advection fog. The cold California Current,
which runs along the western coast of North America, is much cooler than the
warm air along the coast.
Valley fog forms in mountain valleys, usually during winter. Valley fog
develops when mountains prevent the dense air from escaping. The fog is trapped
in the bowl of the valley. In 1930, vapor condensed around particles of air
pollution in the Meuse Valley, Belgium. More than 60 people died as a result of
this deadly valley fog.
Freezing fog happens when the liquid fog droplets freeze to solid
surfaces. Mountaintops that are covered by clouds are often covered in freezing
fog. As the freezing fog lifts, the ground, the trees, and even objects like
spider webs, are blanketed by a layer of frost. The white landscapes of
freezing fog are common in places with cold, moist climates, such as
Scandinavia or Antarctica.”
How Does Fog Form?
“The scene can be as spectacular as a view from above showing only the
tops of city skyscrapers poking through or as disorienting as a sheet of gray
directly in front of you.
While common in some locations, fog can simply amaze us.
According to the Glossary of Meteorology from the American
Meteorological Society, fog is a collection of water droplets suspended in the
atmosphere in the vicinity of the earth's surface that affects visibility.
Specifically, fog reduces visibility below 1 kilometer (or 0.62 miles).
Some Common Types of Fog
The most common form of fog, known as radiation fog, typically occurs on
clear nights as the earth's surface cools moist air immediately above it. If
just enough light wind is present – a couple of mph, at most – this chilled air
can be gently stirred through a deeper layer, forming a deeper radiation fog.
Often in the fall, you'll see morning fog hug lower valleys of the
Appalachians. This valley fog, really just a type of radiation fog, results
from cold, dense air draining down mountain slopes at night, collecting in the
valley floors, then forming as any other radiation fog described above.
Incidentally, let's dispel a myth. Fog does not burn off, per se.
As solar energy heats the ground near the fog's edge, vertical mixing
brings drier air into the fog's edge, evaporating it. A typical ground fog will
dissipate first at its edges, where its depth is more shallow, working its way
toward the thicker center of the fog.
Sometimes fog forms when warm air moves over a cold surface. Warm air
moving over snow-covered ground in winter and sea fog drawn inland over a cool
land surface along the West Coast are two prime examples of so-called advection
fog. Unlike radiation fog, advection fog can sometimes be seen as moving
laterally along or near the ground.
When surface temperatures are below freezing, water droplets in a fog
are supercooled, waiting to freeze on contact with any subfreezing surface.
These freezing fog events can be dangerous not only for a reduction in
visibility but also for a light accumulation of ice on roads, particularly
bridges and overpasses.
At even colder temperatures, fog made up solely of tiny ice crystals
will form. This ice fog is common in the winter months in parts of Alaska's
interior, among other locations closer to the poles.
You may also notice steam fog from some lakes in the fall or early
winter. Cold air overlaying warm air near the warm lake surface is an unstable
configuration, lending itself to rising air. The mixing of cool air chills the
warmer, more moist air immediately above the lake to allow condensation and a
cloud to form. You can typically see wispy, vertical currents of fog rising
from the lake.
Some other, less common fog types include:
Frontal fog: If warmer raindrops fall into colder, drier air,
evaporation occurs. Eventually, the cold air moistens sufficiently to produce
fog.
Upslope fog: Air moving gently upward in elevation enough for the layer
to reach saturation, such as behind a winter cold front in the High Plains and
Front Range of the Rockies.
Hail fog: On rare occasions, accumulated hail at the surface can chill
the near-surface air enough to produce a shallow veil of fog.
Most Fog-Prone Areas
The Appalachians, parts of northern New England and the Pacific
Northwest each typically see at least 40 days a year with dense fog (at least
one-quarter mile visibility or lower). Of course, morning fog makes up the
lion's share of these days, after which late-morning/afternoon sunshine is
plentiful.
Parts of the northern Gulf Coast and California coast can also have
frequent fog, if not always dense fog.
In winter, valley fog can hang stubbornly in lower elevations of the
Great Basin, as well as California's Central Valley, as the combination of
warmer air aloft moves over an area just soaked by the storm. Add an Arctic air
mass spilling over the Continental Divide into the Great Basin, and this
so-called "inversion" fog can hang in for days in places like Salt
Lake City and Boise, trapping pollution near the ground, as well.
What about the least foggy location in the Lower 48 States? That would
be the Desert Southwest, from southern Nevada and southwest Utah into Arizona
and southwest New Mexico, averaging only a few days a year of dense fog.”
More links to check out for weather, or fog, related information:
So now I know that the area we live in is one of the
most fog-prone areas in the U.S. Much of this is due to the Allegheny & Appalachian Mountains and our location being in a valley. Thanks for
reading along to the end. Hope you
learned something new along the way and enjoyed the photos and our adventure
living in a foggy area. Please feel free
to comment and share.
