![]() (11, 15-17) In addition to their direct effects on vis radiation, both BC and BrC immersed in cloud droplets absorb light and facilitate water evaporation and cloud dispersion, an additional indirect effect that counteracts the cooling effect of cloud droplet nucleation by aerosols. A new term, “brown carbon” (BrC), has emerged in recent scientific literature to describe this type of aerosol, characterized by an absorption spectrum that smoothly increases from the vis to UV wavelengths. However, certain types of OC absorb radiation efficiently in the near-UV (300–400 nm) and vis ranges. (12-14) Most OC compounds absorb IR and UV radiation strongly but are relatively transparent to visible (vis, 400–700 nm) and near-IR (700–2500 nm) wavelengths. The effects of BC are especially significant in areas that rely on burning biomass and coal. (12) BC absorbs solar radiation over a broad spectral range, from ultraviolet (UV) all the way into infrared (IR). (8-12) The best-known type of light-absorbing carbonaceous aerosol is “black carbon” (BC), which represents soot-like particulates generated by fossil fuel combustion and biomass burning. However, a significant and highly variable fraction of carbonaceous and organic aerosols absorbs radiation. Most organic aerosols (OA) can be characterized as “white” because they efficiently scatter visible radiation. The direct effect refers to direct absorption and scattering of solar and terrestrial radiation by aerosols. ![]() ![]() The cloud albedo effect, or indirect effect, arises from nucleation of cloud droplets and the formation of ice crystals on atmospheric particles. There are two major aerosol effects on the propagation of radiation through Earth’s atmosphere.
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