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Today, many people are aware of the influence of air pollution is affecting the world climate. Air pollution and certain particles can affect the development of clouds. So that the clouds tend to reduce rainfall in dry areas. While the wet areas, rainfall is increasing, accompanied by a very severe storm.
The research proves for the first time the influence of aerosols - soot, dust and other small particles in the atmosphere can influence weather and climate in the world, has been carried out by a team from the University of Maryland.
Aerosols are tiny solid particles or liquid particles suspended in air. They include soot, dust and sulfate particles, and are what we commonly think of when we talk about air pollution. Aerosols come, for example, from the combustion of fossil fuels, industrial and agricultural processes, and the accidental or deliberate burning of fields and forests. They can be hazardous to both human health and the environment.
Aerosol particles also affect the Earth's surface temperature by either reflecting light back into space, thus reducing solar radiation at Earth's surface, or absorbing solar radiation, thus heating the atmosphere. This variable cooling and heating is, in part, how aerosols modify atmospheric stability that dictates atmospheric vertical motion and cloud formation. Aerosols also affect cloud microphysics because the serve as nuclei around which water droplets or ice particles form. Both processes can affect cloud properties and rainfall. Different processes may work in harmony or offset each other, leading to a complex yet inconclusive interpretation of their long-term net effect.
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Greenhouse gases and aerosol particles are two major agents dictating climate change. The mechanisms of climate warming impacts of increased greenhouse gases are clear (they prevent solar energy that has been absorbed by the earth's surface from being radiated as heat back into space), but the climate effects of increased aerosols are much less certain due to many competing effects outlined above. Until now, studies of the long-term effects of aerosols on climate change have been largely lacking and inconclusive because their mechanisms are much more sophisticated, variable, and tangled with meteorology.
Team use the last 10 years of data obtained from the research facility of U.S. Southern Great Plains, Oklahoma (the program is run by the Department of Energy Atmospheric Radiation Measurement). "We have found, for the first time, long term, the net impact of aerosols on cloud height and thickness, and the resultant changes in frequency and intensity of rainfall," said Zhanqing Li, a professor of atmospheric and oceanic sciences at Maryland and lead author of the study.
The study found that under very dirty conditions, the mean cloud height of deep convective clouds is more than twice the mean height under crystal clean air conditions. "The probability of heavy rain is virtually doubled from clean to dirty conditions, while the chance of light rain is reduced by 50 percent," says Maryland's Li, who is also affiliated with Beijing Normal University.
The scientists obtained additional support for these findings with matching results obtained using a cloud-resolving computer model. The study by Li and co-authors Feng Niu and Yanni Ding, also of the University of Maryland; Jiwen Fan of Pacific Northwest National Laboratory; Yangang Liu of Brookhaven National Laboratory, Upton, NY; and Daniel Rosenfeld of the Hebrew University of Jerusalem, is published in the November 13 issue of Nature Geoscience.
"These new findings of long-term impacts, which we made using regional ground measurements, also are consistent with the findings we obtained from an analysis of NASA's global satellite products in a separate study. Together, they attest to the needs of tackling both climate and environmental changes that matter so much to our daily life," says Li.
"Our findings have significant policy implications for sustainable development and water resources, especially for those developing regions susceptible to extreme events such as drought and flood. Increases in manufacturing, building of power plants and other industrial developments, together with urbanization, are often accompanied with increases in pollution whose adverse impacts on weather and climate, as revealed in this study, can undercut economic gains," he stresses.
Source: http://newsdesk.umd.edu/scitech/release.cfm?ArticleID=2551
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