Air Pollution and Atmospheric Visibility

Air Pollution can impact visibility in remote areas as well as in cities.
Click on image for full size (133 Kb)
Source: T. Eastburn

Have you ever spent time in a large city? If so, the odds are you’ve seen the sky engulfed in a brownish-yellow or grayish-white haze due to air pollution. Such haze can reduce visibility from miles (kilometers) to yards (meters). Mountains or buildings once in plain sight can suddenly be blocked from view.

Air pollution that reduces visibility is often called haze or smog. The term smog originally meant a mixture of smoke and fog in the air, but today it refers to any mixture of air pollutants that can be seen. Smog typically starts in cities or areas with many people, but because it travels with the wind, it can appear in rural areas as well.

One consequence of smog over any given area is that it can change the area’s climate. Smog reduces the amount of the Sun’s energy reaching the Earth’s surface. In some cities, this reduction has been as high as 35 percent on particularly smoggy days. The reduction is greatest when the sun is low on the horizon because the sunlight has to travel through a greater amount of polluted air as its angle drops.

A reduction in solar radiation may not be the only thing air pollution inhibits. It may be altering rainfall patterns as well. Particulates in the air often form condensation nuclei that attract water vapor. When enough moisture accumulates around natural dust particles for example, droplets of rain typically fall. But certain specks of air pollution, such as black carbon, can be too small to produce raindrops big enough to hit the ground. Since rain flushes dust, soot, and chemicals from polluted skies, atmospheric visibility could also be negatively impacted as a consequence.

Scientific field campaigns such as MILAGRO are one way scientists can research atmospheric processes to prove or disprove such ideas. For now, if rain isn't in the forecast when atmospheric visibility is low and smog is high, than wind is likely your best hope for a return to clear skies.


Air Pollution's Effects on Us

Air Pollution and Climate

Air Pollution and Atmospheric Visibility

Air Pollution can impact visibility in remote areas as well as in cities.
Click on image for full size (133 Kb)
Source: T. Eastburn

Have you ever spent time in a large city? If so, the odds are you’ve seen the sky engulfed in a brownish-yellow or grayish-white haze due to air pollution. Such haze can reduce visibility from miles (kilometers) to yards (meters). Mountains or buildings once in plain sight can suddenly be blocked from view.

Air pollution that reduces visibility is often called haze or smog. The term smog originally meant a mixture of smoke and fog in the air, but today it refers to any mixture of air pollutants that can be seen. Smog typically starts in cities or areas with many people, but because it travels with the wind, it can appear in rural areas as well.

One consequence of smog over any given area is that it can change the area’s climate. Certain dark particles, such as carbon, absorb solar radiation and scatter sunlight, helping produce the characteristic haze that fills the skies over the world’s megacities. This haze reduces the amount of the Sun’s energy reaching the Earth’s surface, sometimes by as much as 35 percent.

A reduction in sunlight may not be the only thing air pollution inhibits. Some research has supported the idea that certain air particles are altering rainfall patterns as well. Although particles in the air form the nucleus that attracts cloud moisture into water droplets, specks of soot or black carbon may be too small to produce raindrops big enough to hit the ground. Since rain flushes pollutants from the atmosphere, visibility could be negatively impacted as a consequence.

Scientific field campaigns such as MILAGRO are one way scientists can research atmospheric processes to prove or disprove such ideas. For now, if rain isn't in the forecast when atmospheric visibility is low and smog is high, than wind is likely your best hope for a return to clear skies.


Air Pollution's Effects on Us

Air Pollution and Climate

Air Pollution and Atmospheric Visibility

Air Pollution can impact visibility in remote areas as well as in cities.
Click on image for full size (133 Kb)
Source: T. Eastburn

Would you be surprised if smoke from a fire stopped you from seeing nearby buildings or mountains? Probably not. What if there was no fire, and a brown or gray haze filled the sky. Would you be surprised not to be able to see nearby buildings or mountains then?

Smog is the term that is used for such haze in the sky. Sometimes, the sky is so smoggy that visibility is limited. It happens most often in large cities with many people, but smog can also travel to other areas with the help of the wind.

When smog is in the sky, sunlight can have trouble shinning through it. As a result, the climate of the area can be changed by smog. A reduction in sunlight may not be the only thing air pollution reduces. Scientists are researching the possibility that it may also inhibit rainfall.

More clouds usually mean more rain, but not always, especially with certain specks of air pollution. Resent research findings report that particles of soot are often too small to produce raindrops large enough to hit the ground. This is unfortunate, because rain is one way to wash dust, soot, and chemicals from polluted air and allow mountains and buildings near and afar to be seen.

For now, however, more research needs to be done. Scientific field campaigns such as MILAGRO are how scientists gather information about air pollution and its harmful effects on visibility, rain, climate, and so much more. So if rain isn't in the forecast on a smoggy day, it may be best to hope that the wind blows in and the smog blows out.


Air Pollution's Effects on Us

Air Pollution and Climate


Page created February 19, 2006 by Teri Eastburn.
The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. All Rights Reserved. Site policies and disclaimer