Читать книгу Weather For Dummies - John D. Cox - Страница 71

The variety of tiny particles of solids and liquids collectively called aerosols are not, strictly speaking, atmospheric gases. But these natural and man-made impurities in the air are very much a part of the atmosphere. They play important roles in both daily weather and in longer term climate variations.

On the surfaces of these tiny floating bits of stuff, water vapor condenses to form clouds. In fact, my people at the Go Figure Academy of Sciences tell me that you cannot get a cloud to form naturally without this microscopically small flotsam and jetsam up there. Without clouds, of course, there would be no precipitation, and without precipitation — well, you get the picture. There would be no Weather For Dummies!

The atmosphere is carrying tons of aerosols, such things as soot and ash from fires, dust kicked up by winds, salt from sea spray, and large quantities of ash and droplets of gases from the eruption of volcanoes. In fact, the gigantic eruption in 1991 of Mt. Pinatubo in the Philippines threw so much material high into the atmosphere that it changed the short-term global climate. Aerosols from this single volcano filtered out sunlight, causing average surface temperatures in the Northern Hemisphere to decrease by nearly 2 degrees. This worldwide cooling effect lasted nearly two years.

On the downside, industrial processes and gasoline engine combustion releases enormous quantities of aerosols, which is responsible for the formation of smog in urban areas. Chapter 14 describes these and other air-polluting effects of aerosols, including acid rain.