Satellite-derived direct radiative effect of aerosols dependent on cloud cover
Satellite-derived direct radiative effect of aerosols dependent on cloud cover
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DOI：
10.1038/ngeo437
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发表时间：
2009-03-01
影响因子：
18.3
通讯作者：
Charlson, R. J.
中科院分区：
文献类型：
--
作者：
Chand, D.;Wood, R.;Charlson, R. J.
生物质燃烧产生的气溶胶可以通过反射和吸收太阳辐射来改变地球的辐射平衡。气溶胶是否产生净冷却或净变暖效应取决于气溶胶类型和下垫面的湿度（2）。在这里，我们使用一个基于卫星的方法来量化的直接，顶部的大气辐射效应的气溶胶层平流在部分多云的边界层的东南大西洋在2006年7月至2007年10月。我们表明，气溶胶的变暖效应增加与底层云覆盖。这种关系几乎是线性的，使得有可能定义一个临界云分数，在该分数处，气溶胶从产生净冷却作用转变为产生净变暖作用。对于这一区域和时间段，临界云分数约为0.4，并且对气溶胶吸收的太阳辐射量和下层云的反射率非常敏感。我们估计，当考虑云量和气溶胶之间的大规模空间协变时，气溶胶的区域平均变暖效应高出三倍。这些结果表明，云预测的气溶胶直接影响的准确量化的重要性。
Aerosols from biomass burning can alter the radiative balance of the Earth by reflecting and absorbing solar radiation(1). Whether aerosols exert a net cooling or a net warming effect will depend on the aerosol type and the albedo of the underlying surface(2). 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.