By IANS,
Washington : Scientists have proposed a new framework to gauge the effect of aerosols more accurately on precipitation in climate models.
Man-made aerosols are tiny particles suspended in the air – from such sources as transportation, industry, agriculture and urban land use – not only posing serious health problems, but also impacting climate.
Recent studies suggest that increased aerosol loading may have changed the energy balance in the atmosphere and on the earth’s surface, altering the global water cycle in ways that make the climate system more vulnerable to precipitation extremes.
Aerosols also seem to affect clouds, altering precipitation patterns, which may change not only regional water resources, but also the regional and global circulation systems that constitute the earth’s climate.
The proposed framework improves scientists’ ability to simulate present and future climates by integrating, for the first time, the radiative and microphysical effects of aerosols on clouds.
Aerosols radiative effects mostly act to suppress precipitation, because they decrease the amount of solar radiation that reaches the land surface, and therefore cause less heat to be available for evaporating water and energising convective rain clouds.
Microphysical effects can slow down the conversion of cloud drops into raindrops, which shuts off precipitation from very shallow and short-lived clouds.
Model simulations suggest that this delay of early rain causes greater amounts of cloud water and rain intensities later in the life cycle of the cloud. This suggests that rain patterns are shifting, leading to possible drought in one area and flooding downwind in another area.
In addition, greater cooling below and heating above leads to enhanced upward heat transport. Model simulations have shown that greater heating in the troposphere enhances the atmospheric circulation system, shifting weather patterns due to changes in convective activity.
To that end, authors of the study are participating in a new, international research project designed to study the connections between aerosols, clouds, precipitation and climate (ACPC project).
The scientists are affiliated with the International Geosphere-Biosphere Programme (IGBP)
The work appeared in the Friday edition of Science magazine.