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Precipitation - Effects Of Particulate Pollution On Cloud Microphysics

particles droplets clouds liquid

As discussed above, gas-phase pollutants such as sulfur dioxide can be converted into water-soluble particles in the atmosphere. Many of these particles can then act as nuclei of cloud droplet formation. Increasing the number of CCN in the atmosphere is expected to change the characteristics of clouds. For example, ships' emissions have been observed to cause an increase in the number of droplets in the marine stratus clouds above them. If a constant amount of liquid water is present in the cloud, the average droplet size will be smaller. Higher concentrations of smaller droplets reflect more sunlight, so if pollution-derived particles alter clouds over a large enough region, climate can be affected. Precipitation rates may also decrease, since droplets in these clouds are not likely to grow large enough to precipitate.

Resources

Books

Mason, B.J. Acid Rain: Its Causes and its Effects on Inland Waters. Oxford: Clarendon Press, 1992.

Rogers, R.R., and M.K. Yau. A Short Course in Cloud Physics. Oxford: Pergamon Press, 3rd Edition, 1989.

Wallace, John M., and Peter Hobbs. Atmospheric Science: An Introductory Survey. Orlando: Academic Press, Inc., 1977.


Periodicals

Schneider, Stephen. "The Greenhouse Effect: Science and Policy." Science 243 (1989): 771-781.


Cynthia Twohy Ragni

KEY TERMS

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Aerosol particles

—Solid or liquid particles suspended in the air.

Cold cloud

—A cloud that exists, at least in part, at temperatures below 32°F (0°C).

Hailstone

—Precipitation that forms when supercooled droplets collide with ice and freeze.

Mixed cloud

—A cloud that contains both liquid water and ice.

Supercooled

—Water than exists in a liquid state at temperatures below 32°F (0°C).

Virga

—Precipitation that evaporates before reaching the ground.

Warm cloud

—A cloud that exists entirely at temperatures warmer than 32°F (0°C).

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