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Satellite-derived direct radiative effect of aerosols dependent on cloud cover

Nature Geoscience volume 2, pages 181184 (2009) | Download Citation



Aerosols from biomass burning can alter the radiative balance of the Earth by reflecting and absorbing solar radiation1. Whether aerosols exert a net cooling or a net warming effect will depend on the aerosol type and the albedo of the underlying surface2. Here, we use a satellite-based approach to quantify the direct, top-of-atmosphere radiative effect of aerosol layers advected over the partly cloudy boundary layer of the southeastern Atlantic Ocean during July–October of 2006 and 2007. We show that the warming effect of aerosols increases with underlying cloud coverage. This relationship is nearly linear, making it possible to define a critical cloud fraction at which the aerosols switch from exerting a net cooling to a net warming effect. For this region and time period, the critical cloud fraction is about 0.4, and is strongly sensitive to the amount of solar radiation the aerosols absorb and the albedo of the underlying clouds. We estimate that the regional-mean warming effect of aerosols is three times higher when large-scale spatial covariation between cloud cover and aerosols is taken into account. These results demonstrate the importance of cloud prediction for the accurate quantification of aerosol direct effects.

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This work was supported by University of Washington startup funds, NASA’s CALIPSO Mission (contract NAS1-99105), National Science Foundation (grants ATM-0601177 and ATM-0205198) and the National Oceanographic and Atmospheric Administration (grant NA070AR4310282). S.K.S. would like to thank NPP administered by Oak Ridge Associated Universities (ORAU) for an NPP fellowship.

Author information


  1. Department of Atmospheric Science, University of Washington, Box 351640, Seattle, Washington, USA

    • D. Chand
    • , R. Wood
    • , T. L. Anderson
    •  & R. J. Charlson
  2. Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore-560 012, India

    • S. K. Satheesh
  3. NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

    • S. K. Satheesh


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D.C. carried out the bulk of the analysis of CALIPSO data using a retrieval algorithm designed by D.C., T.L.A., R.W. and R.J.C. (plus colleagues at NASA Langley). MODIS cloud data were synthesized by R.W., D.C. and S.K.S. carried out the RTM analysis. D.C. wrote the bulk of the manuscript, with major input from R.W. and T.L.A. R.W. and T.L.A. provided project oversight.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to D. Chand.

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