Clouds rising from aerosols

MOSCOW, November 13 — RIA Novosti. Elevated levels of aerosols in the upper atmosphere, not only increases the number of clouds, but it makes them grow up, "plump", and also increases the amount of precipitation in the rainy parts of the world and deprived of moisture over dry areas of the planet, climate scientists write in a paper published in the journal Nature Geoscience.

A team led by Lee Chzhantsina (Zhanqing Li) from the University of Maryland (USA) analyzed the results of a cycle of long-term observations of the atmosphere (ARM), which was conducted by the Ministry of Energy of the United States since the late 1980s. In this cycle was to monitor the temperature and structural state of the "foot" and "tops" of the clouds, the state of aerosols in the ambient air, as well as wind speed and direction.

Lee and his colleagues analyzed all the clouds, and all forms of precipitation, which were recorded ARM team in the last 10 years. As part of their work, scientists tried to find out the factors affecting the interaction of aerosols and water vapor, studying the so-called cloud "mixed" phase. Temperature of the foot in the clouds above 15 degrees Celsius and the temperature of their tops are always below four degrees Celsius. As they note, such clubs atmospheric vapor the most vulnerable to the impact of aerosols and small changes in the concentration and composition of the dust particles and droplets of liquids affect their condition.

It was found that this type of clouds begin to grow rapidly in height with increasing proportion of all aerosols in the surrounding air. The strongest growth seen among low-altitude clouds at a height of up to 1 km and decreases with increasing distance from the surface of the earth.

As they note, the most strongly this effect during the summer, at a height of up to 3.3 meters above sea level. As the scientists explain, at that point is the freezing point of water, above which aerosols lose much of their effectiveness.

A similar relationship can be traced to the intensity of rainfall. Climate scientists have found that aerosols increase the intensity of rainfall in those parts of the atmosphere, which contains a relatively large amount of moisture, which is often precipitation. On the other hand, aerosols reduce the number of rainfall in arid regions of the U.S..

In addition, aerosols affect the ratio of showers and light rain — increasing their number increases the total number of showers, and the proportion of light rain drops sharply. This can greatly affect the environment in North America, as more than half of the rain, watering the soil of the United States, belong to the category of light precipitation.

Based on these data, the researchers built a computer model of cloud and compared its findings with observations of some clouds in 2006 and 2008. Share of aerosols in the "virtual" cloud was very close to that which was recorded near these clouds of steam. Other parameters — the duration, the type of precipitation and cloud lifetime — different from the real.

The authors believe that their research will help climatologists and other specialists of the relevant international and national authorities to clarify the "contribution" of aerosols in climate change.

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