- The Washington Times - Thursday, April 24, 2003

When people rush through their days, eyes fixed on the pavement, they can miss one of the greatest beauties of the skies: the clouds.
The bodies of fine water droplets or ice particles suspended in the atmosphere up to several miles above sea level often are taken for granted, says Steve Zubrick, science and operations officer at the Baltimore-Washington Forecast Office of the National Weather Service in Sterling, Va., a division of the National Oceanic and Atmospheric Administration in Northwest.
"Each cloud tells a story," he says. "You study clouds because they ultimately contain the basic ingredients that will form precipitation, which is what we want to try to forecast for everyone."
Clouds are among the most obvious features in the sky, and because the assortment of clouds can predict weather patterns, learning about the different types of clouds and how they form can give insight into the weather.
Without clouds, precipitation wouldn't take place on Earth, which probably would prevent life from existing on the planet, says Scott Stephens, a meteorologist with the National Climatic Data Center in Asheville, N.C.
"In order to have precipitation, you need cloud formation," he says. "It keeps the water cycle going."
Clouds get their start when the sun causes water to evaporate on land. When it evaporates, it becomes a gas and rises. The gas cools as it rises, condensing when it reaches a certain level. As the cool, condensing air collects, a cloud is created.
Four basic types of clouds, which can be further divided into 27 categories, can be observed in the atmosphere.
Cirrus clouds, or those clouds with the prefix cirro, usually are made of ice crystals, as their bases form about 20,000 feet into the atmosphere. Typically, the clouds are high, thin and white. They generally occur in fair weather.
Cumulus clouds look like white cotton balls in the sky. These clouds can occur at any level, with the tops reaching more than 60,000 feet into the atmosphere. The more humid the air, the lower the cloud base. Alto is the prefix added when the clouds are at midlevel, between 6,000 and 20,000 feet.
Stratus, which is Latin for layer, describes the type of clouds that cover the entire sky like a blanket. They usually are associated with gray weather, with cloud bases occurring just a few hundred feet above the ground. When stratus clouds reach ground level, they also may be called fog. As fog lifts, it can form low stratus clouds. Strato is the prefix given for low clouds, those with bases below 6,000 feet.
Because nimbus comes from the Latin word meaning rain, nimbo is added to the beginning or nimbus added to the end of the name of a cloud that produces precipitation, such as cumulonimbus or nimbostratus. Usually, nimbus clouds form at 7,000 to 15,000 feet. The bases of these clouds form closer to the ground as the clouds thicken and precipitation falls.
The man credited with initially naming the clouds is Luke Howard, who lived from 1772 to 1864. He worked in England as a manufacturing chemist and pharmacist. He loved nature and the weather, especially the clouds, from an early age. His book "Seven Lectures in Meteorology" was the first textbook on weather. He frequently is referred to as the "godfather of clouds."
More recently, John A. Day of McMinnville, Ore., has dedicated his life to the study of clouds. At age 89, Mr. Day, who holds a doctorate in cloud physics, teaches a course in meteorology during the January term at Linfield College in McMinnville, Ore. He also is the author of several books, including "The Book of Clouds."
Mr. Day, whom many call the "Cloudman," suggests establishing the habit of observing the sky when rising in the morning, before retiring at night and as many times as possible in between. He says such observations can give the viewer a sense of connectedness with nature.
He says watching the clouds "a magic show of the sky" could be an antidote to boredom. Using a cloud chart as a reference that shows pictures of the basic clouds is helpful for any beginning observer of the sky. Notes can be recorded in a journal.
"My passion today is to raise people's consciousness about clouds," he says. "They are missing something that satisfies the soul in terms of beauty. … Look up and see the clouds. Enjoy the panorama of the sky. It adds a new dimension to life. … Think of what it would be like to live in a place without clouds. The skies would be sterile, the same day after day after day."
Beyond their beauty, clouds also insulate the Earth, says Kevin Lavin, executive director of the National Weather Association in Charlottesville.
In fact, the weight of the various clouds can be estimated by finding the weight of the water droplets or ice crystals inside them, which helps scientists know how much moisture is available for precipitation. Aircraft flying through the clouds can measure the water and ice content. That content usually is recorded in grams per cubic meter of air (g/m3). For instance, small cumulus clouds range from 0.2 to 0.5 g/m3, while larger cumulus clouds range from 0.5 to 1.0 g/m3.
Although the clouds seem as light as air, their mass regulates the amount of the Earth's energy that is radiated into space and also protects the planet, keeping too much solar energy from reaching its surface.
Unfortunately, with pollution and smog, some researchers fear global warming, which inhibits the appropriate amounts of energy from escaping into space. As energy is trapped by the clouds, the climate of the planet grows warmer. If less energy is collected, the climate becomes cooler. Understanding this energy balance is essential to answering questions posed by possible climate change.
"We don't know enough about clouds," Mr. Lavin says. "We've been studying clouds for ages, but there are specialists in cloud physics who continue to study them. We try to learn more and more about them every day."
Sometimes, if precipitation is needed in an area, scientists will perform cloud seeding, which encourages the clouds to produce rain or snow, Mr. Stephens says. In warmer seasons, salt is dropped on clouds from airplanes. The salt hastens the transformation of water vapor in the clouds into droplets.
In colder seasons, dry ice or silver iodide is scattered through clouds. Seeding makes precipitation production 5 percent to 20 percent more likely in the cloud, Mr. Stephens says. It converts the cooler water in the clouds into ice crystals, which grow into snowflakes. The snowflakes fall to the earth as snow or melt and fall as rain.
Seeding the clouds is more effective if the atmosphere is leaning toward an environment that is favorable for precipitation.
"You can't just seed any cloud," Mr. Stephens says. "If the overall atmosphere conditions are unfavorable for precipitation, your cloud seeding will not be nearly as effective."

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