Reduction of Tropical Cloudiness by Soot

Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2000-05, Vol.288 (5468), p.1042-1047
Main Authors: Ackerman, A. S., Toon, O. B., Stevens, D. E., Heymsfield, A. J., Ramanathan, V., Welton, E. J.
Format: Article
Language:English
Subjects:
Aerosols
Atmosphere
Boundary layers
Clouds
Cooling
Cumulus clouds
Environmental aspects
Fractions
Heat
Liquids
Ocean pollution
Optical thickness
Pollution
Solar heating
Soot
Water
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Summary:Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here, we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations, the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon).
ISSN:0036-8075
1095-9203
DOI:10.1126/science.288.5468.1042