What are Fog and Smog?

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By Erica Campbell on March 22, 2012, 12:05pm

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Each morning over the last few days, I feel like I have woken up in a castle…deep in the Scottish countryside.  Why?  The fog.  It seems like the fog has been there every morning, greeting me with its mysterious fingers, blocking the light of the sun.  Being someone fascinated with the weather, I decided to find out a little more about fog and its distant “cousin” smog.

Fog is essentially a dense cloud, filled with water droplets, that lies close to the ground.  When temperatures at night are cold and calm, with not a cloud in the sky, radiational cooling occurs.  This is when the Earth cannot hold onto the heat of the day and it (the heat) escapes into space.  As the temperature of the ground decreases, it cools the air above it forming water droplets.  This can form fog.  Fog can also form when warm, moist air travels over a cold surface.  The more water droplets per cubic centimeter, the denser the fog becomes.

The foggiest place in the world is the Grand Banks off the island of Newfoundland.  Other foggy areas in the world include Argentina, Newfoundland, parts of Italy and some areas of California, which can average over 200 foggy days a year.  In fact, many highways in California can suddenly and without warning, become blanketed in extremely dense fog…leaving motorists completely blinded.  The results of which can be devastating. 

Fog also has a distant “cousin” called smog.  The term smog was first used in London, England during the early 1900’s to describe the combination of smoke and fog.  Today, smog is a mixture of pollutants, but is primarily composed of ground-level ozone.  Smog-forming pollutants or ozone comes from many sources, such as car and truck exhaust, power plants, factories, buses, boats, trains and even household items like paints, grills and certain lawn care tools.  In Connecticut, we normally see the occurrence of smog in the warm and humid summer months. 

Large smog occurrences are linked to heavy motor vehicle traffic, high temperatures, sunshine and little or no wind.  Temperature controls the length of time it will take smog to form.  Therefore, it will form faster and be worse on hot, sunny and sometimes humid days.  In fact, smog can be trapped over a city for long periods of time.  Los Angeles, San Francisco, Washington DC, and other major cities in the US are known for having a serious smog problem.  In many countries across the world, there are also issues with smog.  If you recall during the 2008 Summer Olympics in China, smog and air pollution was a major concern for the athletes during the games.

Overall, both fog and smog can wreck havoc on everyday life.  Sometimes it is the feeling of waking up, looking out the window through the fog and wondering if you are really in a castle in the Scottish countryside.  Another time it might be trying to drive through the fog on the way to work.  Finally it could be during the summer, when it can feel as though you are suffocating on the smog filled air.  Whatever it is, when fog or smog occur, it can make going about your daily life a little more interesting.


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Erica Campbell

Town: North Haven, CT  

Reporting for WXedge since March 2012.

Articles: 30

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