Seminal role of clouds on solar dimming over the Indian monsoon region

In contrast to most of the world where solar dimming has changed over to solar brightening since late eighties, dimming continues unabated over the Indian region. This study investigates new insight into the origin of dimming over India. As the insolation at the surface is controlled by aerosols and...

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Bibliographic Details
Published in:Geophysical research letters 2010-03, Vol.37 (6), p.n/a
Main Authors: Padma Kumari, B., Goswami, B. N.
Format: Article
Language:English
Subjects:
Aerosols
Atmospheric sciences
Climate change
Clouds
Dimming
Indian
Monsoons
Sky
solar dimming
Summer
Winter
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Summary:In contrast to most of the world where solar dimming has changed over to solar brightening since late eighties, dimming continues unabated over the Indian region. This study investigates new insight into the origin of dimming over India. As the insolation at the surface is controlled by aerosols and clouds, we tried to separate out the two controlling factors by examining clear and cloudy sky days. From 1981–2006, the rate of dimming is found to be twice as large during cloudy conditions (∼12 W/m2/decade) compared to that during clear sky conditions (∼6 W/m2/decade). The clear sky dimming is attributed to increasing aerosols. While the rate of dimming by clouds is similar during summer and winter monsoon seasons, the increased contribution to dimming by clouds during summer seems to come from increasingly deeper clouds covering increasingly larger area. During winter, dimming in cloudy conditions appears to be due to indirect effect of aerosols.
ISSN:0094-8276
1944-8007
DOI:10.1029/2009GL042133